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English version White Paper 3-D in Cinema and Television v2

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    English version White Paper 3-D in Cinema and Television v2 English version White Paper 3-D in Cinema and Television v2 Document Transcript

    • V2 White Paper 3-D for Cinema and Television TelevisiON Document created under the sponsorship of Document created under the sponsorship of Ficam, the CST, UP3D, the HD-Forum and the AFC and the AFC Editorial Coordination ::Marc Bourhis (Ficam) and Olivier Amato (Smartjog) Editorial Coordination Marc Bourhis (Ficam)© 2012 Ficam
    • Partners for this white paper : The Ficam (Fédération des Industries du Cinéma, de l’Audiovisuel et du Multimédia), presided over by Thierry de Segonzac, is a professional organization bringing together 180 enterprises whose activity covers all the professions and technical know-how dealing with image and sound. Always proposing strong measures, the Ficam represents, promotes and defends the national and international interests of technical industries dealing with audiovisual creation. THE 3D CONSORTIUM The Commission Supérieure Technique de l’Image et du Son (CST), presided over by Pierre-William Glenn is an association grouping professionals in cinema and the audiovisual and multimedia fields, launches 3D rendez -vous as well as technicians and technical artists. The CST brings together today close to 700 members. Its goals are to defend the quality of the production and distribution of images and sound, defend creativity and technological and artistic innovation in cinema and the audiovisual fields, as well as to defend the independence and freedom of action and expression in our professional activities. A UNIQUE MARKET PLACE UP3D (Union des professionnels de la 3Ds) is an association whose objectives are: to bring together and animate the 3-D professional ONE TO ONE MEETING - BUSINESS NETWORKING community, inform and communicate on the professions, know- how and equipment specific to the 3-D world, and to promote and WORKSHOPS - BOARD DEMO PRESENTATION develop 3-D in Europe. Originally composed of 17 members, the HD Forum, presided over 6 ZONES by Jean-Pierre Lacotte, now has 51 members, all professionals as stated in the statutes. The diversity of the questions to resolve around HD has led the HD Forum to create two commissions: the MIDDLE EAST - BRASIL - NORTH AMERICA “technical commission” and the “communication and marketing commission”, which are themselves divided into work groups that RUSSIA - INDIA - CHINA regularly collaborate with the work of the Ficam and the CST. FOUNDED BY : The AFC (Association Française des Directeurs de la Photographie Cinématographique), co-presided over by Matthieu Poirot-Delpech, Michel Abramowicz and Remy Chevrin, brings together most of the SPONSORED BY : directors of French cinematic photography at the highest artistic and technical level of French and foreign productions. The AFC promotes the existence of quality cinematic images, tests new techniques and affirms the competence of photography directors as creative collaborators of film directors, in the best tradition of French cultural and artistic discourse. contact@3dconsortium.biz
    • Special thanks : To Pascal Buron (associate president of Ficam in charge ofthe Research and Innovation technical commission, and to OlivierAmato (Smartjog) for all the coordination work they did on thisproject as they have done on so many others. A big thank you to Yves Pupulin (Bincole) for his contribution TOMORROWto all the chapters of this white paper. Thank you also to OlivierCahen (Stéréo-Club Français) for having shared with us hisencyclopedic knowledge of 3-D and for his editorial contribution to starts here.the visual comfort chapter, as well as to Philippe Gérard (3DLized),who, through his commitment to research on 3-D visual comfort,permitted us to be at the forefront of ideas on this question. A big thank you, too, to Marc Léger (INA Sup) for the writingof the chapter on the main principles of 3-D and the updating of thechapter on codecs and modes of TV distribution.Many thanks to the late Alain Derobe (stereographer andphotography director) who passed away on 11 March 2012, for havingaccepted in due course the taking up again of his contributionmade to the CST concerning the adapting of 3-D to the size of thebroadcast screen, as well as to the members of the CST for theircontribution to the part on 3-D projection for cinema. Thanks as well to Laurent Verduci (stereographer) for hiseducational aids on 3-D which we used as a common theme and ©2012 Cisco Systems, Inc. All Rights Reservedfor his active participation in our work groups. Thanks also to Alain Today, it s easy to marvel at how ar we ve come.Chaptal (Sonovision), Franck Montagné (Imagie), Michel Chabrol Our phones talk to our TVs to record our avorite shows. Doctors in Estonia diagnose(Eutelsat), Thierry Gruszka (NDS/CISCO), Eric Martin (Technicolor), patients in Denmark. Social networks help companies improve customer service.Charles de Cayeux (France Télévisions), Pascal Charpentier And yet, up to now, more than 99% o our world is not connected to the Internet.(UP3D) and Benoit Michel (stereoscopynews.com) for their active But we re working on it. And tomorrow, we ll wake up pretty much everything else you can imagine.participation. Trees will talk to networks will talk to scientists about climate change. Finally, we wish to thank all those who attentively reread Stoplights will talk to cars will talk to road sensors about increasing tra ic e iciency.the final document. Thanks also to David Steiner and Cédric- Ambulances will talk to patient records will talk to doctors about saving lives.Alexandre Saudinos (Parallell Cinéma) for their contribution on the It s a phenomenon we call the Internet o Everything an unprecedented opportunitytechniques of preproduction and filming, as well as to Philippe Ros or today s businesses.(photo AFC director).. Tomorrow? We re going to wake the world up. And watch, with eyes wide, as it gets to work. #tomorrowstartshere
    • 1 SOMMAIRE 0 0 FÉDÉRER ET PROMOUVOIR LES INDUSTRIES TECHNIQUES DU CINÉMA, DE L’AUDIOVISUEL ET DU MULTIMÉDIA 1 Why a White Paper on Stereoscopic 3-D* (3Ds)?? PAGE 8 1 ma 0 Technical industries iné Fundamental Principles of Stereoscopy PAGE 10 0 c of creation audiovisuel RIGS AND STEREOSCOPIC CAMERAS PAGE 20 1 LIVE MULTI-CAMERA 3DS CAPTURING PAGE 24 0 00 1 3Ds POSTPRODUCTION: CORRECTIONS AND WORKFLOW 1 PAGE 25 00 1 1 1 2-D/3Ds CONVERSION: THE NEED FOR KNOW-HOW PAGE 30 1 0 0 0 VISUAL COMFORT WITH 3Ds PAGE 32 0 1 00 1 0 1 0 3Ds PROJECTION FOR FILMS PAGE 34 mult imédi 3-D TV DISPLAY PAGE 36 a 0 ADAPTING 3-D TO THE SIZE OF THE BROADCAST SCREEN PAGE 40 3Ds GLOSSARY PAGE 45 0 With over 180 member companies, APPENDIX 1: DEFINITION OF 3Ds PROFESSIONS PAGE 47 the Ficam represents and promotes the technical industries of Cinema, APPENDIX 2: 3-D FILMING TECHNIQUES PAGE 49 Audiovisual and Multimedia. APPENDIX 3: CODECS AND DISTRIBUTION MODES PAGE 54 www.ficam.fr FICAM (Fédération des Industries du Cinéma, de l’Audiovisuel et du Multimédia) 11/17, rue de lAmiral Hamelin-75783 Paris Cedex 16-Tel : + 33 (0)1 45 05 72 55-Fax : + 33 (0)1 45 05 72 50
    • 8 9 Why a White Paper on Stereoscopic 3-D* (3Ds) ?E ver since movie theaters have been equipped with digital 3-D pro- production. In fact, stereoscopic 3-D, if it adds new possibilities on the jectors, a number of 3-D feature-length films have been shown narrative level, also includes new obligations on the technical level tied with often disparate processing quality. The television market has to the cerebral acceptance of cinema and television viewers. This is why,also decided to respond rapidly to the desire of the public for 3-D films. in this 3Ds white paper, our objective is not to constrain the creativityThe television manufacturers, quick to participate in this technological of directors, who should remain free in their artistic content, but to setcraze, now make flat television screens on a grand scale equipped with a framework for their being better able to get around in the additionaldisplay systems “in 3-D”, allowing the viewer to watch 3Ds TV programs production possibilities specific to stereoscopic 3-D.in conditions of quite acceptable visual comfort. Moreover, some smart- It is also important to specify that the study of stereoscopy,phones have recently appeared in the mass market which are capable already quite old, has allowed the visual comfort zones–inside which aof generating autostereoscopic 3-D. viewer will have no discomfort or, not to say headaches–to be empiri- However, the market for mobile, TV and cinema broadcast cally defined. Scientific studies are now taking place to refine these pa-hardware is much in advance, chronologically speaking, of the produc- rameters.tion capacity of stereoscopic 3-D content by the audiovisual and cinema We say also that the art of 3Ds is only at its beginnings. There will noindustry. Up to now, there does not exist enough natively produced 3Ds doubt be the possibility for directors of films or television broadcasts tocontent to furnish all the ad hoc broadcast media. The barrier is mainly go beyond this technical framework, at least from time to time, in ordereconomic and technological, but it is also a result of a lack of informa- to provoke quite new emotions in the viewer.tion on the practical conditions in which it is possible today to create Finally, it should be noted that the perception of the depth of anfilm in 3-D for television and cinema. object in a 3Ds scene is modified according to the size of the display of Due to the current deficiency in 3Ds content, it should be noted the images (movie theater screens or televisions). This white paper thusthat many 3-D films and programs broadcast in movie theaters, or on describes the different display technologies and defines the technicalthe first 3Ds television channels, use procedures that create 3-D from contours of future 3Ds programs to be provided for television and the cinema.2-D automated images. These do not sufficiently take into account the In fact, in order to summarize the main objective of this whitemain principles of visual comfort for the viewer and put into question paper, we would say that it consists of sufficiently informing audiovi-the notion of respect for the original work. sual and cinema professionals on the possibilities of 3Ds so that they Given this enthusiasm for 3-D, it seemed necessary for diffe- can appropriate this new language as much as possible, and that publicrent professional organizations of the cinematographic and television disappointment can be avoided for this new artistic and technical field,industries (Ficam, CST, UP3D, AFC, HD-Forum, etc.) to produce a white as might have been the case during the first wave of infatuation for 3-Dpaper laying out the current state of stereoscopic 3-D. The goal of this films in the 1950’s.white paper is to point out the different technical and narrative issuestied to the filming, postproduction, visual comfort, 2-D/3Ds conversion This white paper on 3-D refers to the state of the art in May 2012. It is theand display on a cinema and/or television screen. second version of the document that takes into account the remarks of Stereoscopic 3-D is an artistic and technical mechanism requi- French professionals and updates the generic ideas on the subject.ring a mental reconstruction of images, which is chosen by the directorand limited by the physiological laws specific to most viewers. As such, it is crucial to put in place, at every step in the manu- * Rather than use the terms “relief” or “3-D”, quite imprecise for thefacturing chain, 3-D monitoring and quality procedures supervised by former and source of confusion with computer generated images for thequalified personnel and trained in this new mode of creation and post- latter, we recommend using the term “3Ds” for stereoscopic 3-D.
    • 10 11 Fundamental Principles ofStereoscopy How do we perceive 3-D ?L et’s look at a close object: for example Now, while continuing to look at the tip of our the index finger of our hand. Naturally, finger, let us consider the objects situated the optic axes of our eyes convergent behind our finger (Figure 2). On which sidetowards the object being looked at. We thus to they seem to be placed when we close onebecome slightly cross-eyed. The more the ob- eye and then the other? We notice that theyject is close to us, the more we become cross- are more to the left seen from the left eye andeyed: the angle of convergence increases. The more to the right seem from the right eye.more the object moves away, the more the It is what is called parallax. It is said that forangle of convergence decreases. The angle objects situated behind the plane of conver-of convergence is a very important indication gence, the parallax is positive. Let us observefor our brain: knowing the distance between again our finger and now consider the objects figure 1 figure 2 figure 3the two eyes, that are closerit can deduce (Figure 3). Thethe distance of phenomenonthe object, like is inversed: thea range-finder. object is more toThe brain allows the right seemus to perceive from the leftthe depth of the eye and morescene by way to the left seemof the differen- from the rightces between eye. For objectsthe angles of situated in frontconvergence of of the plane ofthe different ob- convergence, thejects being observed. Now let us examine the parallax is negative. In sum, the parallax isimages formed by our two eyes: as the optic zero for all the objects situated in the planeaxes of our eyes converge towards our finger, of convergence, positive for all the objects si-the image of our finger is formed at the same tuated behind the plane of convergence andplace on our two retinas (Figure 1). We call the negative for all the objects situated in front of figure 4same points of the objects in the left and right the plane of convergence. are then practically parallel and the angle of object can hardly be perceived. Happily, otherimages “homologous points”. It is said in this The more an object is distant, the more the convergence becomes too small to inform us indications inform us of the depth: occultation,case that the homologous points are fused perception of its distance is imprecise. When sufficiently as to the distance of the object. Be- relative size of the objects, perspective, the ef-and that our finger is in the “plane of conver- the distance of the object goes beyond several ginning from a 100 meters, the distance of an fect of mist, etc.gence” of our eyes. dozen meters, the two optic axes of our eyes
    • 12 13 consequently the placing of the plane of How is 3-D reconstructed? 3Ds applied to cinema Stereography : a new production language convergence as well as the amplitude of the “scenic box” (see Appendix 2).W and television Creating for the cinema or for television is It should be noted that the size of the 3Ds T e now take two cameras in pla- not tied only to the techniques of produc- he fundamental difference between tion or broadcasting, but also to the emo- monitoring screen during filming does not ce of our two eyes along with a attempts in the past and the present necessarily correspond to that of the fi- tional connection that these images foster 3-D screen system whose role growth of 3Ds comes from the tech- nal broadcast. The stereographer should in the human brain. From this standpoint,is to make each eye see only the image nical mastery of 3-D in the entire chain of 3Ds requires that this connection be re- clearly inform the production team of thethat is intended for it. In Figure 4, the left the manufacturing and image broadcasting considered so as to adapt the conditions differences in the sense of depth accordingand right homologous points are repre- process. The use of computer tools during of creating a cinematographic or televi- to the dimensions of the film’s intendedsented respectively in red and cyan. If the shooting and the possibilities of modifying sion project to this question. 3Ds induces screen and to justify his “not visual” buthomologous points are superimposed du- images pixel by pixel up to broadcasting a rupture with the practices of production “provisional” adjustments.ring projection, the view will converge on are steps that from now on are indispensa- and which modifies the interpretation of The parameters of “depth” can be in- ble and in constant evolution. They guaran- the space as imagined by the director. One creasingly modified in postproduction. Gi-the screen and the object will be seen on tee the quality of the 3Ds image necessary should also note that, in studying certain ven this fact, just as the color calibrationthe plane of the screen. That is how one for the visual comfort of the viewer. gives the tone of the scenes in a film, the filming parameters such as lighting andsees films in 2-D. Digital tools take part in the mastery of “3Ds calibration” becomes an important framing, if there is a rupture between 2-DIf the parallax is positive, the view will stereoscopic production. Being more and 3Ds, it is situated more on the side of step after the film has been edited. It al-converge towards a point situated behind knowledgeable from this experience, we acceptance by the viewer’s brain than that lows for the perception of reality in 3-D tothe screen: the viewer will thus have the wish today to support the emergence of a of artistic practice. be given a general tonality and to provideimpression that the object is situated new cinematographic and television lan- In 2-D as in 3Ds, the director remains the 3Ds continuity between shots according tobehind the screen (as if seen through a guage tied to the usage of 3Ds. main judge of the use of 3-D in order to the final intention of the director.window). Finally, if the parallax is nega- A purely technical conception of 3Ds is serve his narrative, whether it is a question a risky bet. It is preferable to rely on the of a film, a telefilm or a televised program. Think about 3Ds before filmingtive, the view will converge towards a point savoir-faire, both technical and artistic, of In the same way that he decides a produc- If you want to have a quality 3-D effect, itsituated in front of the screen, and the the stereographers and technical service tion in 2-D, he formulates a particular re- would be useful to verify beforehand theobject will thus seem to be in front of the companies, which have both a solid theo- quest to the stereographer who will see to pertinence of the choice of 3Ds for this orscreen (as if popping out). retical knowledge and experience in 3Ds. its completion. The working together of the that film or television program from theIn sum: The production of a sequence in 3Ds can- director and the stereographer thus aims beginning of the synopsis or scenario. In• Objects situated on the plane of conver- not be summed up in an automatic algo- to establish “3-D behavior” (modulation of this way, a story unfolding in an aerial orgence during filming will be reconstructed rithm for creating 3-D effects, however the stereoscopic range), done through a aquatic universe lends itself totally to aon the plane of the screen (parallax zero). sophisticated it may be, or do without the graphic image or annotations on the script popping-out effect, for the objects can be• Objects situated behind the plane of onsite experience of specialized professio- or storyboard, which then serves as a guide “unglued” from any support, like levita- nals who know how to adapt to particular for the team doing the shooting. 3-D that ting in a fluid or a vacuum. Furthermore,convergence during filming will be re- filming conditions, very often full of unfo- is too strong can lead to visual discomfort longer shots and/or rather slow and fluidconstructed behind the screen: window reseen events. The creation of a 3Ds scene over time, while 3-D that is too weak risks movements of the cameras also favor theeffect (positive parallax). requires a perfectly regulated production frustrating the viewer. It is mainly within perception of a more comfortable 3-D ef-• Objects situated in front of the plane of with the camera angles completely maste- these limits that the director can choose fect. They leave time for the public to dis-convergence during filming will be recons- red. If the production teams are not sup- the depths he wants. The streographer cover and enter into the depth of the ima-tructed in front of the screen: popping-out ported by competent people in this way, translates these choices using the tools ge. In the same way, wide compositionseffect (negative parallax). they risk having their possibilities limited at his disposal, tools which he will super- with framing using high-angle or low-an- as to the creation of emotions in the viewer vise in their practical use. Given this, he gle shots favor 3-D effects and intensify specifically tied to 3-D effects of depth or is responsible for the adjustment of the sensations of dizziness. Geometric forms, of popping out, or even in certain cases, to angulation and the inter-axial distance buildings for example, are more quic- provoke visual discomfort in the public. between the center of the camera lenses kly identified by our brain and contribute according to the chosen focal length, and to the quick immersion into 3-D. As for
    • 14 15 Creating a 3-D Scene streaming programs, among the first ex- ted cases: periments taking place today using 3Ds in - The shot itself, as in a classic film. Ideal- retransmission of sporting events, football ly, the storyboard creator should create a From the beginning of writing the scenario, 3-D can be taken into account and used as a is looked on as the favorite due to the high storyboard that is optically correct. narrative tool. It is possible to imagine scenes whose dramatic intensity will be amplified if number of viewers and a public potentially - A view “from the side”. Starting from the one plays with the depth, the popping-out effect and the effects of gigantic size and minia- interested by the fact of viewing matches principle that the 3Ds window is projec- turization. The scriptwriters can think about 3-D effects in advance, sometimes integrating in 3-D. Nevertheless, the current produc- ted onto the plane of the screen, this side their ideas directly into the scenario. These can be indicated in capital letters (in the Anglo- tions of this sport on television, centered view will mark the location of the plane of Saxon world, they are sometimes preceded by the term “3DFX”). Nevertheless, the logical on lateral panoramas and a depth of field the screen so as to distinguish the objects process of creating a film lends to entrusting the control of stereoscopic effects to the director often difficult to master, is not necessarily that should be in front of the plane of the and/or stereographer. For example, in Océanosaures (Sea Rex), a 3-D IMAX© film written the best adapted to retransmission in 3D, screen (popping out) and those that should and directed by the Frenchmen Pascal Vuong and Ronan Chapalain, the stereoscopic filming unless the camera angles and the pano- be behind it (in depth). proposals appear right from the storyboard. ramas are comple- - In the most tely rethought out complex cases, aOcéanoSaures - Voyage au Temps des Dinosaures © 2010 - N3D LAND Productions with respect to view from above, It should be noted in the case of this film a 2-D retrans- with the location that Pascal Vuong created the storyboard mission. A fur- of the plane of the himself and Ronan Chapalain supervised ther constraint screen, could also the stereography, thus allowing each shot comes from the be useful. to be conceived very early in all its depth fact that the ac- Beyond these and not as a 2-D image. In this storyboard tion takes place general rules, © Convergence3D.net extract, the colored markings added to the most of the time it could also be initial drawing permit one to quickly loca- far from the ca- advisable to use te the elements to be popping out and the meras, thus re- previsualization position of individuals in relation to the quiring the use software that si- plane of the screen. This stereoscopic pro- of a long focal mulates what the duction information, added to the framing length on the basis shot or perspec- and cropping choices, allows the director of wide 3-D shots Screen capture of 3Ds previsualization software tive will be in or- and film crew to better prepare the shoo- that could create a der to define the ting and postproduction of the images and “maquette” effect. camera angles prevent certain pitfalls of stereography en- On the other hand, certain inside sports, and movements in 3Ds. Such software al- visaged too late in the process. such as basketball, where one can be clo- lows computer-generated images to preci- ser to the action, offers 3-D that reinforces sely reconstitute each filming location and the viewer’s emotions. the camera position (whatever the type of rig). It allows the frame, the inter-axial dis- Preproduction tance, and the angles to be calculated and Preparation is essential in order for fil- previsualized during filming and in post- ming in 3Ds to be successful. Researching production. All the parameters, such as particularly meticulous points (measuring the focal length, the diaphragm, the depth distances, verification of distant objects, of field, the movements, etc., can also be taking into account the size of the 3Ds rig) predetermined. permits many problems to be avoided in advance. Creating a 3Ds storyboard is ad- The importance of checking volumes vised. Without help from software, this sto- During the work of identifying certain para- ryboard could show, for each shot, at least meters and of preparing a film in 3Ds, it is two or more views for the most complica- necessary for the director and the head of
    • 16 17photography to check the frames by taking lengths, the establishing of the position of one of the fundamental parameters. It is when there is a blurred background withinto account the development and distri- the massive forms of the film set becomes what happens within the shot or out of it backlit foliage.bution of volumes relating to depth. They even more decisive in determining the po- that justifies the movement of the camerarely on the stereographer who helps them sition of the actors and the viewpoint of according to the director’s decision. Inin looking for homogeneity in the choice the camera in terms of the depth and the Using visual indications of depth for 3Ds streaming programs, the frame is deter-of angles and focal length in relation to edge of the frame. The sensation of 3-D, productions mined much more by following the action,3Ds. This step should allow the position even if it appears realistic or admissible Creating a shot in 3-D does not only mean which in sports for example, is generallyof the objects to be determined within the for a single shot, might no longer be so adjusting the stereoscopy, but also to use centered.“scenic box” containing the volumes of the during the editing of several shots one af- information that is going to ease the un-scene in three dimensions. This checking ter another. For example, during filming in derstanding of the depth of the image.is of major im- 2-D, it is normal to A camera in movement It is thus necessary to know how to use Moving shots reinforce the perception of both stereoscopic and non-stereoscopicportance. “cheat” in the po- the succession of volumes within the sce- information.At this step, a sitioning of the ne. This emphasis of volumes is obtained, Painting and photography remind us thatwarning is neces- actors (to make a of course, by the movement of the actors in 2-D numerous factors allow the brainsary to point out shot or perspective in relation to the objects in the frame. It is to analyze and understand the depth of anthat, as opposed easier). This prac- equally increased by the camera’s view- image. This faculty is conserved, moreo-to 2-D images, tice should arouse point, which reinforces the presence of the ver, when one eye is closed. The utiliza-stereoscopic the greatest vigi- actors. Perhaps this could be a new type of tion of this non-stereoscopic informationviewing provides lance when using space between cinema and theater? makes the understanding of space, andthe viewer with 3Ds.the perception the participation of the sensation of 3-D,of the position Framing Lighting in 3Ds easier to experience. Among these fac-in depth of each If, in 2-D cinematography, light and its tors, we can cite the following: The precision ofobject, and thus contrast are only limited by the projection -An object up close masks an object far the cinematogra-their sizes. The standards and, in this context, the power away. This effect, which can be obtained by phic frame is onechoice therefore of the projector, it is quite otherwise in the movement of the actors or the objects of the essentialof the 3Ds fil- stereoscopy. Strong contrasts, in particu- in the depth of the scene, is reinforced by parameters of 2-Dming parameters lar at the edges of the shot, through fo- the movement of the camera’s viewpoint. filming. Yet, withcan lead to a si- liage against the sunlight or between dif- The dollies, the movements of the cra- stereoscopy, whe-tuation in which ferent parts of the subject, can lead to real nes or steadicams, or the movements of re we are nearera person can be cerebral discomfort for the viewer. a shoulder-held camera, emphasize the to low and/or highperceived as a The lowering of contrast is often advised, relative position of objects in relation to 3-D effects, thegiant (magnifi- without us knowing how to precisely each other. frame shows acation) or like a Visualization of the benchmark visual comfort slight uncertainty quantify it today. This being so, shots for -The size of objects decreases with distan-drawing on card- zone as regards 3Ds. which the lighting and contrast levels are ce. This can be used to “cheat” in certain in relation to theboard (flattening), not controllable require sensors covering shots, provided that a likeness is preser- two shots beingor like its opposite a large range in order to obtain images ved with the effects of reduction in size, if filmed, which only overlap completely on(a maquette or stretching effect). capable of conserving 3-D in high and low a realistic image is to be conserved. the plane of convergence or the plane ofFinally, it is useful to note that, as a ge- the screen. Furthermore, the notion of the lighting. This also allows a better adjust- -The gradation of textures: bricks, gras-neral rule, 3-D is best appreciated when immersion of the viewer for certain ste- ment of contrast during the calibration ses, pavements, etc., become less definedthe scene is in movement, close to the ob- reoscopic productions is often emphasi- of stereoscopic films and TV programs. with distance.ject and with a rather short focal length. zed even before the notion of framing, in Likewise, it is advised to pay attention to -The “atmospheric dispersion” (mist ef-Nevertheless, it is difficult to produce a IMAX© for example. But for most cinema- clipping of strong lighting, for such lighting fect): it is due to the pollution of the mi-whole film without close-up shots. For tographic productions, the frame remains can produce a disparity of form between lieu being passed through according to itsshots resorting to medium and long focal the two stereoscopic images, such as thickness. It works for infinite distances
    • 18 19 Managing the Popping-out Effect Popping out is one of the effects is to be weak and slow if the the capacity of the viewer to belonging to 3-D. It gives the intensity is to be strong. The “read” comfortably the effects feeling that the objects pop same popping out can vary in of popping out: at the beginning out of the screen towards the intensity and be produced twice: of a film, around three seconds viewer. first weak then strong, in order are necessary for the brain to However, there are rules to to reinforce the final effect. The submit to the interval between follow so that this effect does not total length of the effect cannot convergence and accommodation cause any visual discomfort. The be too long. For reasons of visual that is imposed on it, whereas elements or parts of elements comfort and of concern for a after ten minutes of a film in 3-D that pop out must be contained narrative balance, the frequency stereoscopy, this accommodation within the field of the cameras. of popping out throughout a time is reduced to half a second. The speed of the appearance of film or a TV program must be It is thus strongly advised against popping out must not be too slow an intelligent dose between the abusing the effects of brutal or too fast. A sufficient time must repetition of popping out and popping out at the beginning be left for the viewer’s brain to their differences in intensity. of a film, for they can become get accustomed to this effect. Finally, it has been noticed painful and wrongly interpreted To preserve the visual comfort, empirically that there is a by viewers’ brains.. Modulation example of the stereoscopic range for the length of a film it must be fast if the intensity phenomenon of learning in Stereoscopic range and modulation of stereosco- is, moreover, variable according to the pic ranges individual.as well as for a smoke-filled room. understanding depth. This is why certain The stereoscopic range is a measure of Some scientific studies are, however,-The effect of perspective is very important head operators prefer using light that is the quantity of 3-D in an image. It is the still going on in France (3-D Acceptanceinformation: as we look, we search in per- more directional than in 2-D in order to difference between the interval of the most & Comfort) and in the United Statesmanence for a scene’s convergence lines emphasize the shadows. Regions without distant object and the interval of the closest (BanksLab, University of California atto understand its perspective by using detail of an image—for example a comple- object in a shot. Berkeley) to clear up the relation betweenroads, railways and buildings. tely white sky or an interior scene with to- The stereoscopic range can vary within a stereoscopic range and visual comfort.-3-D is above all comparative. The brain tally black zones—are less favorable to the shot, between two shots and during the Without 100% reliable reference points inperforms better in comparing, for exam- comprehension of 3-D than a cloudy sky or length of a film. Within all these cases, one this domain, we recommend, during theple, colors than in analyzing them. It’s the an interior in which half-light allows the can speak of “modulation of stereoscopic production of a teaser or a test, to examine,same thing for stereoscopy. A distribution subtlety of the details to be seen. ranges”. case by case, the contentious shots thatof volumes in the depth of a scene will fa- -One must also attend to the consistency of The stereoscopic range (histogram of deviate from the “acceptable” limits ofvor the impression of viewing in 3-D. It will the screen depths and avoid the “collision” disparities) is a quantifiable data for each stereoscopy.be more difficult if there is only one ele- of a title placed on the plane of the screen image in percentage of its size or in pixels. In general, it is customary to moderate thement in the foreground separated from with an object that is popping out. As for The term “depth budget” is sometimes exceeding of these limits in favor of theanother element placed at infinity without a “window violation”, it is characterized by used to designate either a stereo range or production.any intermediary volume. For example: a the collision of the edge of the screen with the modulation of stereo ranges, which can It should be noted that there already existsbee popping out on a background of infi- an object that is popping out. lead to confusion. technical recommendations defining thenitely distant mountains will not favor the The same stereo range gives a weak acceptable limits of stereoscopic rangesimpression of viewing in 3-D. It is important to use all of this information to impression of 3-D on a small screen, for 3Ds TV broadcasting (ex: BSkyB-Furthermore, it is sometimes preferable 3-D). The establishment of technical enrich the stereoscopic production parameters. stronger on a movie screen and veryto have titles popping out on a textured powerful on a giant screen such as recommendations is currently under studybackground rather than on a black one. In a general way, the least contradiction between IMAX©. The acceptance by the viewer of in France.-Textures and shadows are stereoscopic monocular and binocular (that is, parallax) depth a stereo range chosen for a given screenobjects, supplementary “information” for information cannot be allowed.
    • 20 21Ensuring the continuity of the modulation of the each other on more or less sophisticatedstereoscopic range during a whole film mechanical or motorized rigs. The advantageIt is indispensable to think of a 3Ds film or of this arrangement is that it is often moreTV program in its entire continuity. For ci- rigid and avoids the aberrations linked to thenema in 3Ds, like in 2-D, the order of se- mirror set up.quences and shots at different steps in the Its inconvenience is that it imposes wide inter-making of a film are often modified, and axial distances which results in a “maquette” Binocleparticularly when it is being edited. effect tied to the apparent miniaturization ofThe modulation of the stereoscopic range the objects being filmed. It is not known howmay be modified by the inversion of shots to avoid this effect today, but it comes intoduring editing. For example, a close-up play from the moment one goes beyond the Two types of side-by-side rigswith much popping out will correspond ba- inter-axial distance of human vision. It can bedly with a wide landscape shot having a lot put up with, or even looked for, according toof depth: this alternation tires the viewer. how the director wants his production to be. shots in a fiction film. advantage of having its vertical camera placedIt is thus necessary to take care in the or- In any case, there is no other solution when Mirror rigs are used with steadicams, shoul- above the mirror, allowing the optical axis toganization of the shots to ensure smooth one films from far away, with objects in the be brought very close to the ground for ma- der-held cameras and most classic machi-transitions of depth for the public. foreground situated far from the camera king large vertical low-angle shots. nery. Mirror rigs are conceived or arranged in and one wishes to have 3-D. This is the case, two ways when they can be turned around the for example, for certain shots taken from a helicopter. optical axis: Integrated 3Ds camera -The first, called zenithal, favors the protection RIGS AND STEREOSCOPIC of the mirror. The vertical camera is placed Also appearing on the market are professio- nal video cameras that record two views of Semi-transparent mirror rigsCAMERAS The cameras are placed vertically at a 90° an- under the optical axis and directed upwards. the same scene through two optical axes in- This arrangement allows for a simpler protec- tegrated within the same camera body. ThisA gle to each other and find themselves in opti- tion from lights interfering with the mirror. “rig” is an adjustable support on which type of wholly integrated technology has cal concurrence in a semi-aluminized mirror. movie cameras can be arranged and -The second, called “crane position”, has the the advantage of limiting problems of dis- This mirror, also called a “beam splitter”, al- set up. There are two types according lows one camera to film through the mirrorto whether the cameras are placed side-by- and the other to film by reflection on the re-side or as a mirror (beam-splitter). It is the flecting side of it. Binocleneed to obtain or not a small or large inter- For this process, the transmission through,axial distance that determines the choice of a and the reflection from, the mirror is equalrig. If a large inter-axial distance is desired, to 50% each so that the loss of a diaphragm,usually for helicopter or distance shots, a si- induced for the camera filming through thede-by-side rig is used. mirror, is identical, or almost so, to the otherThe sophistication of side-by-side or mirror one. The mirror thus permits filming with anrigs is not linked to the device but to the inter-axial distance equal to 0 and thus bedefinition made by the manufacturer. Certain freed from the problems related to the spacemanufacturers make rigs that are versatile used by the cameras and lenses.and are simply assembled differently to be It is thus possible to reduce the inter-axialinstalled either as a side-by-side or mirror distance to 0 mm, which allows for the ca-rig. meras to be perfectly aligned. The mirror rig mainly permits small inter-axial distances,Side-by-side rigs indispensable for filming close to the sub-Two identical cameras are placed next to ject, which is the case in a large majority of Simplified schema of a semi-transparent rig
    • 22 23 METHODS FOR ALIGNING AND DR SYNCHRONIZING 3Ds CAMERAS A stereoscopic shot requires paired equipment (cameras and lenses) andthe stereographer’s utmost attention to the adjustment of the rig during shooting.Not being able to have perfect alignment once the shooting starts, it is necessaryto continue working thanks to real-time correction algorithms for television, andin postproduction for cinema. It is a question of bringing to the viewer two imagesperfectly aligned vertically pixel by pixel.Factors provoking troublesome vertical disparities:- Difference in height of the optical axes (whether they are parallel or cross verti- Two examples of integrated 3-D camerascally)- Difference in the placement of one camera in relation to the other parity between the two stereoscopic points To this end, technical creation industries have- Difference, even minimal, between the focal lengths of the cameras and the of view to be superimposed, especially pro- seen, since the end of the 90’s, the rise offocusing of the lenses blems of alignment, differences in focusing, motion control rigs capable of being precisely- Different optical aberrations between the lenses of zooming, etc. However, the integrated paired electronically via a computer. More- Trapezoid effect resultant in vergence on the object. 3Ds camera has the drawback of generally recently, 3Ds image analysis instruments It’s a question of minimizing as much as possible these disparities when offering only a single setting for the inter- have arrived with, notably, the possibilityfilming. On a side-by-side rig, the optical axes are placed in parallel aiming at axial distance and a limited adjustment of of making a precise real-time drawinginfinity, and a test card is used at 3 meters to verify that the altitudes have been vergence. These restrictions result in heavy out of problems of disparity between tworespected. On a mirror rig, the same procedure is used in placing the inter-axial constraints when filming a close-up scene in stereoscopic images and correcting them indistances at 0. In both cases, test cards and a 3Ds monitor is used to precisely 3-D, and, more generally, does not allow for real time.adjust the alignment, if possible to the size of a pixel. complete control of stereoscopic production All these factors make it so that today one Likewise, that the colorimetry and luminosity of the cameras are identical through adjustment of the two parameters sees hardware and software solutions appearshould be watched over closely. Certain tools on the 3Ds monitor allow this to be inter-axial distance and vergence. from several components manufacturersprecisely monitored. for processing 3Ds shots in real time,Synchronization of the camera sensors at the pixel level is indispensable. The non- Progress of 3Ds rigs and monitoring of disparities which allows certain corrections—such asrespect of this rule on moving images leads to visual fatigue by the viewer. Whatever the talent of the stereographer, vertical disparities, detection of rotation and For the timecode, the cameras must be connected with one camera as TC involuntary disparities between the two trapezoid deformation—to be automated.“master” and the other as “slave”. viewpoints of the cameras remain. It is Certain software also permits automation As to scanning, putting one camera in Genlock master and the other indispensable to correct them when filming of the inter-axial distance and convergence.in Genlock slave is not precise enough, except for certain miniature cameras or live. For fiction, these defaults can also be Solutions of this kind, conceived in France orcameras conceived for this purpose. It is preferable therefore to have recourse to an corrected on the film site so that rushes can elsewhere, which allow these problems toexternal synchronization camera body in Tri-level Sync, connected to the camera be viewed comfortably. In postproduction, be corrected or parameters to be monitoredGenlock inputs. if these defaults are very minor and do in real time, are already being used on film Cameras without the Genlock input, such as digital photo cameras, are not bother the editing process, certain sites, particularly in live sports productions.problematic. Certain 3Ds monitors allow, however, scanning to be viewed and to stereographers prefer to usefully make these 3-D correctors are also being integratedtry “manual” or “on the fly” synchronization by triggering the cameras simulta- corrections during the “3-D calibration” into visualization tools used in fiction orneously. But this does not provide the indispensable guarantees need for a feature stage. This consists in adjusting the 3-D for capturing in order to judge the effectsfilm project or for live television. values for a shot or between two shots. It obtained without mental strain for the team. ensures the consistency of the 3-D effect for the length of the film.
    • 24 25 LIVE MULTI-CAMERA 3Ds A modification of workflow should be consi- As a general rule, it should be noted that all 3Ds POSTPRODUCTION: dered in the 3Ds production unit. In fact, each the actors who intervene in the live streamCAPTURING stereoscopic source should undergo 3-D cor- should have 3Ds visualization: slow motion CORRECTIONS AND WORKFLOW rection before being integrated into the grid operators, synthesizer operators, special ef- ALive multi-camera 3Ds capturing implies ac- or the mixer. This correction can be multiple fects technicians, etc. ccomplishing postproduction in 3Dstions in real time in order to preserve 3-D ho- and specific to each rig. It encompasses the is not very different from traditionalmogeneity. The first action consists in analy- flip image in the case of a mirror rig, geo- The difficulty of live 3Ds multi-cameras today postproduction, if only that it is neces-zing new actors and organizing them into the metric correction, compensation for opti- is not only related to technical problems, but sary to manage file volumes twice as large.production team’s hierarchy. The director is cal centering, etc. Whatever the nature and also to the calling into question of the pro- It is also necessary to ensure the continuitythe one who conceives the stereoscopy of a number of corrections applied, they should duction. It is quite clear that the acceptance of depth in 3Ds scenes, by watching over theproject that puts the stereographer and all be done in a very short time since this period of 3-D is directly dependent on the quality of sequence of their stereoscopic ranges andthe technicians to work. comes before mixing. Today, this processing the stereoscopy, but it is also necessary to by correcting the disparities between the leftA single stereographer guarantees the qua- time varies from 40 to 120 ms. provide the necessary information for a good and right images. When filming fiction, theselity of 3-D capturing. He works in concert The quality and number of 3Ds visualizations narrative. Due to this fact, live broadcasting defaults can also be corrected, of course,with the director of photography. He is assis- is a key element of a 3Ds production tool. is a dangerous exercise in 3Ds. For example, before reaching the postproduction stage.ted by the convergence operators who are in Two cases are possible for the production: to if one wishes to bring information captured However, if these defaults are very minorcharge of the stereoscopy of one or two axes. propose a multiviewer which includes all the by a 2-D camera into a 3Ds stream, one can and do not interfere with editing, certainHe continuously regulates the inter-axial sources as well as the program and preview resort to a real-time 2-D/3-D transfer, or if stereographers prefer to make these adjust-distance and vergence according to the va- in 3Ds. This requires a certain vigilance in or- one wishes to provide a score or a time, one ments during 3-D calibration, or, in any case,riations of frame, focal length and focus. der to exclude from the mosaic any camera would proceed by inserting 3Ds elements these 3-D adjustments are reviewed in termsBy analogy with photography, it is necessary being adjusted. The second option consists into a 3Ds image. These techniques are to- of consistency over the length of the film.to integrate this team into the live production of keeping the sources in 2-D visualization lerable for the viewer as long as they areunit in order to make discussion easy and and to put only the program and preview in mastered. 3Ds. Viewing is at the heart of the process of 3Ds editingguarantee a consistent program. The postproduction of 3-D images requires
    • 26 27 OPTIMIZING LIVE 3Ds COSTS IS POSSIBLE ! ting tools, this is rarely the case. copyright : Technicolor For this reason, during “offline” editing of 3Ds films or programs, it is imperative to Concerning the additional costs related to 3Ds capturing, the figure of 25 to 30%more than view 3Ds edited shots and to validate them 2-D capturing is often put forward, but according to those in charge of AMP VISUAL TV these regularly on a stereoscopic screen having figures are relative. The additional costs greatly depend on the length of the capturing itself, a size near to the one that will be used for and AMP VISUAL TV hopes to have, in the end, enough production streams in 3Ds to be able the final showing. In this way it is possible to identify at once the visual discomfort resul- to have economies of scale. What is most important today is to find methods for reducing the ting from the non-corrected stereoscopic installation and preparation times. If it is possible, for example, to have two cameras/lenses disparities or the different 3-D values used used only for 3Ds capturing, it would then be possible to considerably reduce the preparation in different shots. Example of correcting geometric time before shooting. But for this to happen, it would be necessary to have a greater volume of If possible, it is even desirable that the conti- disparities production than there is today. nuity of the shots be studied during the pre- paration phase of filming in order to make the 3-D space consistent before and aftera return to more rigorous methods of work after editing, during or just before the stage the transition by reducing to the maximumthan before, and to a more precise definition of calibrating the 3-D of the film. It is done by the differences in distance and convergenceof each person’s task, from preparation of a stereograph technician having experience of the cameras. Nevertheless, adjustmentsfilming to postproduction. These precau- with the correction tools, under the direction are often to be planned in postproductiontions, taken before the various operations, of the stereographer who has already wor- through horizontal transfer of the left and Flare: a source of visual discomfortlimit the alternation of inconsistent 3-D se- ked on it during filming. right images.quences. The change in location of the space to whe-However, even if a stereographer has per- Continuity of shots during editing of 3Ds images re the viewer is attracted, from one shot tofectly adjusted the rigs and taken care to stereoscopic range at the end of the prece- The rhythm of shots edited in stereoscopy another, can also cause visual discomfort.limit the “bad” connections between shots, ding plan consistent with the beginning of is logically slower than that of editing of 2-D Thus the necessity of an appropriate scriptthe editor, will in all likelihood, as in the case the next one. images, for when there is a change of shot, it and a specific “3-D calibration”, making theof 2-D, change the editing order that was is necessary for the brain to have one secondplanned at the beginning. Due to this fact, to appreciate the new universe to be explo-it will be necessary to again verify the conti- red. Learning to watch 3-D by the viewer Adapting convergence and editing:nuity between shots during each viewing of can, however, reduce the accommodation 3-D continuity between two shotsthe 3Ds already-edited rushes. time necessary for each change of shot. ButFurthermore, following the planned post- as of today this is only a supposition. In 3Ds, convergence between two successive shots must be adjusted. Usually, the convergence shotsproduction method and the production bud- In order to limit mental discomfort and re-get, it might be useful to take some time to will be brought closer during cropping in postproduction if they are too different. Otherwise, the duce adaptation time between each shot,correct the involuntary disparities between it is also possible to use the “3-D dissolve” viewer may feel visual discomfort. The time this adjustment takes can also vary. Experiences thatimages. This would mean to correct the- method which smoothes the passage from took place during the production of Legend of the Guardians: The Owls of Ga’Hoole (2010) broughtse geometric and colorimetric disparities one 3-D shot to another when the 3-D ef- to light the fact that the softest transition in 3Ds is obtained when the vergence of entrances into abetween the left and right images such that fects are obviously too different.each of the homologous pixels is situated at shot is progressively adjusted according to the previous shot. In this film, the length of the vergence Because of these constraints, it would bethe same altitude. It must be kept in mind more practical in the absolute for stereos- adaptation time between shots varied from one sequence to another from 8 to 40 images. Further-that these corrections, necessarily made for copic editing to take place “online”, directly more, rather than making the depth characteristics of each shot exactly correspond to the level ofa live capture, should become a postproduc- from already-corrected stereoscopic ima- the cropping point, it was noticed that for most of the sequences, it was possible to eliminate onlytion operation for fiction. ges. However, for reasons of visual fatigue 50% of the difference in depth between shots, and to leave a slight upsurge in 3Ds when cropping.This operation could be made on the rushes over time, but also for the sake of economybefore editing, but today it is generally done Of course, nothing prevents one from using a brutal 3Ds connection between shots to provoke a and/or the non-availability of online 3Ds edi- particular sensation in the viewer.
    • 28 29 Hunting down contrasts that are too strong the parameters of each element in real time,Two types of 3-D according to objects entering into Speed, acceleration and the trajectory of the Since 3Ds broadcasting systems (polarizing and, if possible, on the size of a screen clo- filters and glasses, liquid crystal glasses, sest to that of the definitive broadcasting sizethe shot cameras etc.), do not have an absolute separating in order to take into account the magnifica-The viewer feels visual discomfort if one The movements should preferably be fluid power, each eye more or less perceives a tion factor.of his eyes sees part of an element that and slow, with slow accelerations and dece- phantom of the image destined for the other The special effects person must be trained inthe other eye does not yet see coming into lerations and trajectories in wide curves. If eye. It is thus necessary to limit contrasts 3-D and know how to measure and preciselythe shot from the side. A wise compromise the scenario imposes rapid effects far from that are too strong between foreground place the different elements of a compositebetween the intensity of the 3-D effect and such recommendations, reduced 3-D should and background elements according to the image in a stereoscopic 3-D scene. The pla-the speed of entering into the shot will need be chosen: in the extreme, the optical axes intensity of the 3-D effects and the created cing of these elements must necessarily beto be determined. This does not pose a pro- of the left and right cameras can be blended horizontal disparities. very precise. The objective of the visual effectblem, on the contrary, when this entering little by little so that one films in quasi-mo- is to modify the perception of the 3-D space ofinto the shot is made either on the plane of noscopy, thus preserving visual comfort. It each element to be integrated by using:convergence (plane of the screen) or verti- must be added that rapid movements, espe- Adjusting the light for popping-out effects • The horizontal transfer of the left and rightcally (from the top or bottom of the screen), cially towards the observer, can give rise to To reinforce the sensation of immersion, the images, modifying the convergence point andfor in these cases both eyes see the same ocular fatigue. visual field of the viewer must be filled. The thus the depth location of each object in theelement appear at the same instant. best thing is to progressively dim the zones scene (“horizontal shift”). of the popping-out object that cut the edges • The resizing of the images after the removal of the frame. To do this, a method consists of the parts that are not common to the left The case of a film having “heavy” digital visual effects? in reducing the light of a scene progressively and right views (“crop” and “resize”). towards the edges of the screen. The volume • The correction of the vertical disparities, Concerning geometric and colorimetric defaults, there is a tolerance threshold beyond which the of the filmed scene then seems to be entirely especially trapezoid effects (“keystone”) due viewer gets tired, and it must be admitted that there is a certain imprecision in the correction of centered on the viewer. to the convergence of the two cameras. these defaults. On the other hand, the fine tuning of different elements of a composite image must be accomplished with “zero tolerance”. It is for this reason that the SFX supervisor takes charge of Matte painting in 3Ds all the image’s 3-D manipulations: Matte painting is a technique that can always Adjusting convergence in postproduction 1 - Correction of geometric and colorimetric defaults as well as putting the image filmed in be used in 3Ds for distant scenery, in bac- It is important to note that 3Ds convergence can be adjusted in postproduction and espe- convergence in simultaneous parallel mode. kgrounds toward infinity, where the 3-D set- cially for special effects sequences contai- 2 - Creation and assembly of the composite image’s elements. tings are closest to human vision and without ning visual effects (see box). In this case, 3 - 3-D fine tuning of these elements, in particular in the case of assembling live and computer- real perception of 3-D. However, it is indis- filming often takes place in “parallel” mode, generated images. pensable in this case to create a matte pain- and convergence is done in postproduction, 4 - Putting the composite image in convergence, and 3-D calibrating for the projection screen. ting that is very precisely integrated into the which is much simpler. Important note: when there is filming for a composite image (special effects), it is not recommended “composite” 3-dimensional space. It is no longer convergence that is adjusted, to correct the defaults of the 3-D image before the special effects, because this step produces a The distinguishing of composite stereosco- but the position of the image according to destructive “filtering” that harms the quality of the special effects at the end. pic 3-D elements by the viewer is in fact is the depth: the whole image being brought Besides the SFX supervisor, a certain number of positions can be identified whose work methods much more keen than within a 2-D image. closer or set farther back, and this without should be adapted to 3-D images: An imprecise composition of a 3-D image will deformations. It should be noted that a -rotoscopy be immediately seen as incoherent by the viewer, and even more so when the size of the small part of the side of the images will be -tracking lost, while the vergence on the set will lead -compositing broadcasting screen is large. to a rather slight loss at the top and bottom -matte painting and all work of changing the palette of the image during the elimination of the -computer-generated graphics Compositing in 3Ds trapezoid effects. The computer graphics artist in charge of this work must be labeled “3-D ready” in order to In order to precisely composite the different guarantee the quality and productivity of his work. elements of the final scene, it is necessary to Management of 3Ds files acquire the tools for viewing and modifying More and more shootings in 3Ds use cameras
    • 30 31that record in “file mode”. It then becomes 2-D/3Ds CONVERSION illusion that he sees from two different view- steps and intervention of a specialist remainvery important to recover the X and Y infor- points. indispensable without which the possibilitymation from the cameras to integrate them THE NEED FOR KNOW-HOW exists of providing insufficient visual comfort.into the metadata. In 3Ds postproduction, one C Filming in 2-D while respecting 3-D constraints A number of disparities between the image’sof the main questions is the management of hoosing conversion according to filming two viewpoints must be corrected manually. However, when filming in 2-D in view ofstoring these files, which becomes crucial. Likewise, when distant objects are blurred in conditions converting to 3Ds in postproduction, it is im-The best thing is to opt for regular backups the original 2-D image, the infinite in the re- Today, several American blockbus- perative to film while already extrapolatingof the images as production proceeds, for the constituted 3Ds image must be redefined. It ters shown in movie theaters in 3Ds are the the 3-D effects and in keeping in mind thequantity of data to be processed is doubled. is also necessary to recreate some 3Ds ma- result of conversion of 2-D images into 3Ds constraints pertaining to 3-D. This is how theThe method that consists of editing online terial in zones where the 3-D effect is pro- in postproduction. The main reason is econo- beginning shots, when characters are oftendirectly in 3Ds is most often used for short nounced. mic and comes from the fact that producers, cut off during filming in 2-D by the edges ofprograms (publicity, corporate films, docu- in front of the obstacles related to filming in the frame, can prevent using popping-out ef-mentaries, etc.). This method assumes that 3Ds, prefer to respond to the demand of the fects in the scene. One can slightly cheat to Automatic 2-D/3Ds conversion: an aberration…there are enough editing stations sufficiently 3-D digital movie theater market through have a slight popping-out effect, but with the Most of the current automatic conversionpowerful to process 3Ds images in full reso- 2-D/3Ds conversion, often easier to manage risk of generating the beginning of visual dis- systems provide stereoscopy processed onlylution and in real time. when it has to do with films integrating a comfort in a section of the public, especially in the sense of depth and immersion without large number of digital special effect shots. if this choice is repeated throughout the film. popping-out effects. These machines workLonger editing For example, for the needs of creating 3-D it More generally, shots could have superb with the help of algorithms resting, amongThe editing of a 3Ds project is accomplished is possible to cut out persons who have been popping-out effects provided that the frame other things, on a principle of color recogni-in certain cases from a single point of view, filmed with a green background and to re- is kept “airy”, which requires the cameras to tion, with distribution organized on the factfor example, the left image. To appreciate process scenery in 3Ds that has been trac- pull back or to have the foreground charac- that warm tones are mostly in the foregroundthe consistency of the final editing, it will be ked by a virtual camera. Usually, this sce- ters moved back or recentered. of a scene and cool tones in the back farnecessary to make regular conformations in nery will have been stretched out in matte Certain transitions and dissolves already in away. The only problem with this so-called3Ds, allowing the editor to modify the struc- painting with computer-generated images place in a film or TV program shot in 2-D are “natural” rule is that it includes many excep-ture and rhythm of the film according to the of creatures inserted into the scene and, in going to have to be adapted to the constraints tions, for the simple reason that one is in an3-D effects obtained. this case, the stereoscopic processing of the of the transitions between 3-D spaces, or artificially lit universe where, when someone film can become more expensive and more else there will be volumes overlapping each has some clothing with a cold tone in the fo-Lengthening the calibration time difficult to manage than a 2-D/3Ds conver- other without any spatial coherence. reground, warm tones may be observed inThe calibration of the 3Ds calibration screen sion in postproduction. Consequently, putting 2-D images into 3-D the background. Due to this fact, automaticshould be made according to the technology of It is also possible to mix techniques within is a technical process demanding the grea- conversion generates many visual artifactsthe glasses used (passive or active). Besides, it the same film. Such “composite” projects test care to prevent visual discomfort or and ambiguities. These ambiguities areis difficult to plan the calibration (colorimetry then consist of shots filmed in 3Ds and even rejection by the viewer, all the while going to quickly turn the viewer away fromand density) with 3Ds glasses being used for others converted from 2-D to 3-D when the respecting a certain realism in 3-D. During this type of image which gives a truncatednumerous consecutive hours without having sequences are easier to process by 2-D/3Ds 2-D/3Ds conversion, the 3-D should be set view of reality.ocular fatigue. Usually, calibration is done in conversion rather than by filming. This is the up essentially to ensure the visual comfort2-D. Then, during viewing in 3Ds, a correction case, for example, of sequences filmed with of the viewers, with beautiful window effects …needed for 3Ds program processingis applied on the viewing screen (LUT) to com- long focal lengths in stereoscopic mode that but with few effective and comfortable pop- However, TV broadcasters will be quicklypensate for the effect of using glasses when can give the effect of successive “slabs”. ping-out effects given the difficulties in set- constrained to use automatic conversionviewing the images. This flattening effect, due to filming with ting them up. from 2-D to 3Ds in order to accomplish pro-At this stage, it is necessary to adjust the ste- long focal lengths, is especially irritating gram continuity between different programsreoscopic range of the film, also called “3-D when filming a close-up portrait shot. Then Correcting disparities in 3Ds sufficiently smooth and acceptable tocalibration”, or to modify the colorimetric the simplest and most economical thing to 2-D/3Ds conversion, accomplished automa- the viewer, such as, for example, betweencalibration according to the 3Ds perception do is to film the sequence in 2-D and then tically with the help of postproduction ma- trailers and publicity that have been madeconstraints. add contours to the face using rotoscopy of chines, is certainly becoming more and more with different 3-D settings. the person such that the viewer is given the efficient, but it is no less clear that manual
    • 32 33Animation in computer-generated graphics, matte truly have two viewpoints of the objects (one cherche (France), has the goal, among other - flicker, when the left and right views are al- for the left eye and the other for the right things, of corroborating the results of labo- ternately shown too slowlypainting and stereoscopy eye). For this type of precise shot, a classic ratory tests with a more restricted panel of - when the colors or brightness of the leftAll the shots of a film or a TV program using output of a film or TV program in 2-D can- 3Ds viewers. A vast study using the general and right views of the same element in thematte painting for background scenery not be recovered to be used as a basis for public should be published during 2012. A image are too unequalshould be studied before postproduction if 3-D. It is thus necessary to take up again all small sample of people has already been put - the contradictions between monocular andconversion from 2-D to 3Ds is desired. It is the 3-D files used in compositing with matte under visual constraints that are supposed to binocular indications of depth, particularlyespecially indispensable to determine which paintings and digital visual effects. provoke problems in order to objectively de- those that result from a default in synchro-matte-painting elements should be recrea- fine certain indications of discomfort. Some nization during rapid side movements, orted by 3-D computer-generated graphic examples are: loss of visual acuity, increased “window violations” that make it so that anmodels in order to obtain a second camera movement of the eyelids, contraction of the element of the image is both, because of itsviewpoint that is visually consistent. VISUAL COMFORT WITH 3Ds pupil, slowing of the change in orientation parallax, seen in front of the window, but hid-For matte painting of background scenery to- I of the ocular axes, loss of binocular fusion, den by itwards infinity, it is possible in fact to “cheat” t often happens that viewers of 3-D films etc. - images that are too complicated (high spa-by creating 3-D through compositing. Our complain of visual fatigue, nausea or dis- Among the diverse causes of visual discom- tial frequencies)human perception of 3-D towards infinity comfort. This dissatisfaction can have two fort with 3Ds, most of the studies concentra- - movements that are too quick by certainis, in reality, almost nonexistent (due to the main causes: ted on the visual disparity between the two elements in the image so that the viewersmall distance between our two pupils com- -defaults during the making and/or broad- viewpoints in relation to convergence and does not have time for binocular fusion topared to the distance separating them from casting of 3Ds content accommodation. While in natural vision our take place before the image completelyobserved objects). It is thus possible to easily -rejection of the artistic means (rejection of ocular system converges and accommodates changesfool the brain through this type of composi- its use or disinterest) on the same object, the viewer of a 3Ds film Each of the visual discomfort factors acts inting operation. In-depth studies on the main causes of visual accommodates on the plane of the screen, a very different way from one person to ano-For matte painting and digital visual effects discomfort with 3Ds for the viewer are made but converges towards the objects that at- ther. When creating 3Ds content, one mustcloser to stereoscopic virtual cameras, one from samples of representative groups. tracts his attention and can be situated just be very vigilant concerning each of these pa-must, on the contrary, model the scenery in The 3-D Comfort & Acceptance project, fi- as easily on the plane of the screen, in front rameters.3D computer-generated graphics in order to nanced by the Agence Nationale de la Re- of it or behind it. We hope that the current scientific studies will establish clear physiological thresholds, Wide variability according to the person and in so doing define more precisely the RELATION BETWEEN ACCOMODATION But the effective limits noticed are extremely possibilities of creating 3-D that is agreeable AND VERGENCE IN 3Ds variable from one person to the next: a small to watch. proportion of people are less sensible to dis- parities in the lower limit of this “comfortThe zone in blue corresponds to the zone of ordinary, zone”, whereas another small proportionsharp binocular vision of a normal subject (ZVBSN). This will only feel discomfort more than five timesdiagram shows how in natural vision the demand for ac- the higher limit. The most well-known causes of visual dis-commodation and vergence in the human ocular system comfort with 3Ds are mainly:are covariant in a way that can be predicted according to - divergence of the ocular axes (heteropho-a linear relation (demand line). In 3-D vision (3Ds), this ry) - amplitude of variations of angular parallaxcoupling is no longer in perfect concordance and can lead - vertical disparitiesto convergence accommodation conflicts causing stinging - “orphan” elements in the image, that is, vi-and/or irritation of the eyes, headaches, etc. (asthenopic sible in one eye and not the other, especially if they attract the attention (very bright, forsymptoms). example)
    • 34 35 ter sends a synchronization signal, adjusting the synchronization. reflected by the screen’s canvas, To not tire a person’s vision, it is which easily allows all the seats to be important that the synchroniza- covered. Several transmitters can be tion of the display of the images, placed in large theaters. using the switching of separator The classic movie theater screen can systems for each eye, is perfect. be kept. The less the gain is high, the These adjustments are to be made better the result will be in terms of for each installation. quality (in particular the uniformity of Polarization of light the luminosity). Polarization of light Active shuttering The viewer has “active” glasses. The- 3Ds PROJECTION FOR FILMS se glasses are equipped with liquid crystals For the record, this principle has also been theater. Uniform values of lighting are thus whose orientation can be modified. Accor-T used for a long time with 35mm projection. he 3Ds projection technology currently A light polarization system is placed in front obtained that are very inferior to the recent ding to the eye and the synchronization si- used in movie theaters is based on the of the projection lens. It is a question of al- standards for digital projection (ISO, Afnor). gnal sent by the infrared transmitter, these sending of two distinct and successive ternately polarizing light in opposite circu- While acceptable for 3Ds projection whose liquid crystals will alternately block theimage streams, and a system allowing each lar states. All the images intended for the qualitative characteristics are not standar- viewer’s vision or let the light pass through.eye to only receive information intended for left eye are thus projected with a polariza- dized, this particularity is very damaging Each eye thus sees the image intended forit. tion in one direction, and those intended for for the quality of 2-D projections. It is thus it, and only this image (no “ghost” effect).Three technological solutions are proposed the right eye with polarization in the oppo- recommended that theaters so equipped be The glasses should be supplied with elec-to accomplish this separation: site direction. To accomplish this, systems dedicated to 3Ds. Furthermore, this method tricity to activate the LCD command circuits.• Polarization of light of liquid-crystal filters (RealD solution) or is not very appropriate for wide theaters with These glasses are relatively expensive and• Spectral filtering of light rotating disks (MasterImage) are placed in little depth. also quite fragile. They are usually “rented”• Active shuttering front of the lens. A connection to the GP/IO To perceive the images separately, the viewer to the viewer for the time of the film, whichAll of them come up against a real problem port of the projector ensures the synchro- wears glasses having a filter for each eye, requires logistics for recovering and clea-of light output, for on average between 75 nization of these filters with the display of each only allowing light to pass according ning them. The main suppliers are Xpand,and 85% of the light stream is lost in the the images. to its polarity. This filtering is not perfect, Volfoni and E3S.systems (filters, glasses). The power of Problems could appear with the projection and each eye perceives a little of the imagexenon burners being limited (currently a window, since most glass integrates light intended for the other eye, thus generating Color filteringmaximum of 7000W), the dimensions of a depolarization layers for security (espe- a slight double image called “ghosting”. In The principle of this technology is to filterlightable image using 3Ds projection with cially fire). order to get around this problem, DCP files by bands using a wavelength comb filter.a single projector are necessarily limited The light is reflected by the surface of a type called “ghost images” can be used, that is, Two techniques have been developed, one(14 to 15 meters in cinemascope format). of “metalized” screen. In fact, it is a screen integrating an inverse image of the parasite by Dolby (based on an Infitec patent) andBeyond that, it is recommended to use two painted with a paint containing aluminum image for each eye. The glasses are sold to one by Panavision.superimposed projectors. The luminosity of elements. This paint has the distinctive fea- the viewer (very low cost) who can keep and The Dolby solution inserts a color filteringthe images is a fundamental factor in the ture of keeping the polarization of the light reuse them for other projections using the wheel into the light path, between the lampperception of stereoscopic effects. when it is reflected, which is not the case same technology. and the matrices (three bands per eye, sli-Another difficulty is the fluidity of the pro- with classic mat white canvas. The two main providers of this type of tech- ghtly offset for each). The rotation of thisjection. In order to improve this problem, On the other hand, these metalized canva- nology are RealD and MasterImage. wheel is synchronized with the alternateand thus to improve the perception of 3-D, ses are very directional, that is, they reflect display of images for each eye. A colorime-each image is projected three times (triple most of the light according to the effective/ Active shuttering tric processing must be made at the serverflash) in the space of one image, that is six reflection axes. Concerning the projector, there is no mo- level in order to reinforce the chromatic se-images altogether in 1/24th of a second This results in a “hot point” whose loca- dification. An infrared transmitter is simply paration of the two images. This requires a(three images per eye). tion varies according to where one is in the connected to the GP/IO port, generally pla- server able to do this processing.The last difficulty in 3-D projection is in ced behind the cabin window. This transmit- The Panavision solution requires that the
    • 36 37 right images is successive. Concerning to High Definition TV. It is what all the televi- ColorCode, who, thanks to a system of ma- the projector, the same lens can be used. sion manufactures say and which explains naging the separation of colors, allows this It is also possible to display two images the very rapid marketing of 3-D televisions already old principle of creating stereoscopic “top-and-bottom” or “side-by-side” on in 2010, even if the content does not exist to- images on television to remain alive a bit lon- the matrix (for example, if it is 4K). In this day in sufficient quantity. ger. case, it is necessary to replace the lens by The other explanation for the rapid deve- a double-lens system. This is the solution lopment of 3Ds televisions comes from the taken by 4K Sony projectors. The polarizing Polarized panels and passive glasses improvement of the quality of the display The principle of passive TV3Ds glasses passive systems are used in front of these technologies and in particular the frequency with a polarized screen surface placed on double lenses. Recently, it is also possible of refreshing flat screens that allow this to a classic LCD panel is a technology used to use active glasses. take place above 200 Hz. Given this fact, it is by certain consumer electronic brands. The possible to propose quality 3-D while crea- principle of its display is based on a filter ha- The technological battle between passive and ac- ting a minimum number of undesirable ef- ving a circular polarization in one direction tive systems fects for the viewer. for even lines and a polarization in the oppo- 3Ds cinema projection systems use a To really understand, however, the problems site direction for odd lines. In this way, each Color filtering wide variety of different technological of displaying 3-D images on a television, it is eye only sees the lines corresponding to its principles. It is the sign of an emerging first necessary to recall the main technolo- direction of polarization. market which is in the process of clo- gies and to provide information on specific The main advantage of passive glasses re-whole lens be replaced and a fixed filter be sing in today on a battle between the rules related to this new mode of television sides in the fact that no electronics areinserted behind the back interior lens. This principle of passive projection of the type display. embedded in them since the glass only hasfilter separates the light spectrum for each RealD or Dolby and the active system of the “static” polarization. These glasses are li-eye (five bands per eye). type XpanD. This competition in the movie Exit anaglyphs ght, the colors are quite correct and there isThe classic movie theater screen can be theaters between two competing techno- As an introduction, we note that it is possible no flickering effect. On the other hand, withkept. The less the gain is high, the better logies, each having its advantages and in- to visualize 3Ds images on a traditional televi- passive glasses each eye only receives a halfthe result will be in terms of quality (in par- conveniences, will no doubt be influenced sion through the transmission of an anaglyph an image on the vertical resolution plane.ticular the uniformity of the luminosity). by the arrival of new light sources in the image filtered in red and cyan. This already Furthermore, with this display technology,The viewers are furnished with glasses that D-Cinema (Laser) projectors, which clearly old possibility is still used sometimes on when the head is inclined in relation to thefilter the light spectrum and allow each eye improve the quality of comfort when 3-D today’s televisions, but broadcasting in ana- television screen, diaphonic effects appearto only view the images formed from the projection is used. Likewise, the techno- glyph has only a single advantage from now like in the technology used with “active”color triplets intended for it. This filtering logical rivalry in movie theaters is likely to on: from the encoding of the video up to its glasses. Here, the circular polarization al-must be very precise and requires the stac- be decided in the course of time by choices display on the television it is not necessary to lows the head to be inclined up to a certainking of around 50 layers of colored plastic taken by large electronic manufacturers in have a specific broadcasting infrastructure. point, after which the polarization of the li-film. Furthermore, as these chromatic fil- the mass television market, which little by On the other hand, this technique suffers ght causes loss of luminosity and colorime-ters require the light to pass through at an little propose for both technologies more from serious limits concerning visual com- tric changes.angle of 90°, the glasses are specially sha- and more refined and comfortable techni- fort. It intrinsically generates a loss of colorped to allow the eye to move without losing cal solutions for the viewer. fidelity. In particular, depth information is TV3Ds with active glassesthe 3-D effect. lost in those parts of the image having the In 2010, most of the television manufacturersThe glasses are very costly (less than ac- same colors as the red-cyan filters. Even lost accepted a TV3Ds display technology usingtive ones). They are usually “rented” to the sometimes is the capacity of the eyes to fuse.viewer for the time of the film, which re- 3-D TV DISPLAY Also noted is discomfort due to the disparity active glasses. This technology is based onquires logistics for recovering and cleaning flat screens having at least a double refresh of luminosity between the left and right filters frequency (even frequencies of 400 and 600them. With the passage to stereoscopic 3-D, the of the glasses. Hz), that are combined with 3-D active glas- development in terms of visual sensation for To be quite complete, it must be emphasized ses. The shutter frequency of active glassesDisplaying the images the viewer is much more pronounced than that the anaglyph process has been refined is synchronized with the display of imagesFor all these systems, the display of left/ during the passage of standard definition TV these last years by companies like Trioviz and on a flat screen. In this way, each viewer’s
    • 38 39eye only sees alternately the image that is principle is essentially the same as lenti- 3-D images to be made and thus limits de top-and-bottom in 720p50, 1080p25, 720p60intended for it. cular network autostereoscopy in which a facto, on a technical and economical level, and 1080p24.This technology is for the moment almost filter (the barrier) alternately distributes the production of content in this displaythe only one to offer a 3-D image with full the points of view intended for each eye. In mode, at least for now. 2-D/3Ds conversion in the television setresolution for television, even if companies contrast to lenticular networks, the lateral Dans la mesure où le relief créé par un réalItlike RealD, JVC and Samsung now market positions for seeing the whole image are A single connection for 3Ds: HDMI 1.4a will be several years before TV3Ds natively-a Full HD passive TV3Ds technology near all at the same distance from the plane of The new HDMI 1.4a (High Definition Multi- produced 3-D content becomes widespread,to the Z-screen system used in movie thea- the image. It thus permits switching more media Interface) connection defines the new especially due to the high additional costs ofters. This new approach should permit the easily from 2-D mode to 3Ds mode, which formats and timings for stereoscopic image production and postproduction generated bypolarization direction to be alternated on is not so evident with a physical lenticular information furnished to televisions through this new technology. From now on, televisionthe whole image, thus offering a Full HD network. readers and decoders. The HDMI 1.4a stan- manufacturers, far in advance of the nativepolarized system for TV. These two technologies represent a strong dard, launched on 4 March 2010, has impro- 3Ds content production market, have deci-The only drawback to the “active” glas- p o t e n t i a l for development ved several functions of the HDMI connec- ded to integrate real-time converters of 2-Dses technology is, for in the future of tors, including the possibility of conveying images to stereoscopic 3-D images in theirexample, when the TV3Ds display most of the stereoscopic 3-D signals used latest generation of televisions.synchronization me- technology in so for broadcasting today. Among these si- This conversion function for the viewer ischanism of the glas- far as they allow gnals, there are the “Compatible Frame” usually accessible with the help of a simpleses is defective. In this the viewer to do modes based on classic image resolutions, remote control. It acts only in the sense ofcase, double images without glasses. where the two images share the horizontal the depth of the image through a heighte-(ghosting) can appear, Autostereoscopy, (side-by-side) or vertical (top-and-bottom) ned sensation of immersion in the scene.which is a nuisance as 3-D immedia- resolution. 2-D/3Ds conversion in the television set isfor the viewer. The tely visible without These broadcasting modes are intended, not conceived so as to produce objects thatproblem also results glasses, already above all, for the TV transmission of 3-D pop out from the screen. Such automaticin diaphonic image represents, mo- content, while the existing infrastructure 2-D/3Ds conversion in the home also causesinformation of the left reover, a convin- can be used for the transmission in high-de- frequent artifacts, exaggerations of 3-D oneye onto the right eye cing medium for finition (HD). Thus, where HDMI 1.3 allows parts of the image that may quickly gene-and vice-versa, while the Panasonic P55VT50 3Ds television marketing and only one HD image to be transmitted, which rate visual fatigue in the viewer.periods of each eye being communication ap- means all diffusion modes of type side-by- So, even if it has yet to be proven by anopen for too short a time plications: public side, top-and-bottom and checkerboard, epidemiological study, it is already knowncan lead to a reduction in places, dynamic dis- that is 3Ds with loss of resolution, the HDMI with certainty that such on-the-fly 2-D/3Dsluminosity. play, museums, airport halls, etc. 1.4 standard allows the transmission of two conversion of video sources that have not On the other hand, autostereoscopy is for HD images, or 3Ds in full HD. been conceived using native support or inAutostereoscopy now still reserved for events and corporate As examples, there are several image for- postproduction to be broadcast in 3-D (ra-The principle of autostereoscopy is based communications or even as a display inten- mats compatible with the HDMI 1.4a interfa- pidity of editing, continuity of shots, para-on two distinct processes: ded for a single individual (telephone and ce: 3-D field alternative (interlaced), frame sitic objects in the foreground, etc.) leads- An LCD panel in front of which a video game consoles, smartphones, etc.). packaging (top-and-bottom format with full to enough parasitic effects so that the in-lenticular network is placed so that an ob- It has, in fact, two major constraints: the resolution by view), complete alternation of terpretation of the 3-D by the human brainserver only sees, for each eye, one column viewer must be in front of the screen and/ lines, half side-by-side, full side-by-side and becomes quickly uncomfortable with heada-of pixels at once. One simply has to use a or to not move too much in front of it to keep the principle of 2-D broadcasting plus depth ches eventually occurring.matrix of two images together (one pixel out a comfortable stereoscopic effect. Further- metadata. It should be noted that HDMI 1.4of two) so that each eye receives a different more, to allow the viewers to be freely pla- works with 3-D flat screens that support Adjusting the intensity of 3-D in the televisionimage in real time and so the stereoscopic ced in front of an autostereoscopic screen, it definitions and broadcasting frequencies as In so far as 3-D created by a director is moreeffect is produced. is necessary to display eight different came- different as 720p50, 1080p25, 720p60 and or less comfortable for the viewer accor-- The parallax barrier is the other ra views enmeshed in a single image. This 1080p24, but also horizontal side-by-side ding to his own visual perception and theimportant autostereoscopic technology. Its therefore implies the production of complex mode in 1080i50 or in 1080i60, as well as
    • 40 41size of his screen, certain television and ADAPTING 3-D TO THE SIZE OF to the camera. It is thus possible to recali- to broadcast the film, because the content3Ds decoder manufacturers are beginning brate all the stereoscopy of a production by created for a large screen will always beto offer manual or automatic adjustment THE BROADCAST SCREEN making a simple side offset of the stereos- viewable on a smaller screen, even if the 3-D Tof the depth of 3Ds scenes. Whatever the here exists several phenomena and copic images. will be more subdued, whereas in the oppo-electronic system used, it is clear that such rules that govern the viewing of ste- site situation, content planned for a smalladjustments made by the viewer cannot be reoscopic 3-D images that we have Calibration of 3-D according to the size of the screen cannot be viewed on a large screenproposed at a level of 3-D going beyond that summarized in the following diagrams, without provoking visual discomfort due to projection screenconceived at the beginning of the program’s and which should serve as a guiding thread divergence. If one considers that the perception of 3-Dproduction, the minimum level being, of when creating the preproduction of a TV Therefore, a film planned for a screen of 20 depends on the size of the image and posi-course, a flat image in 2-D. program or film. meters at its base can always be projected tion of the viewer, the adjustments of 3-D depth and popping out must be fine-tuned on a screen of 2 meters at its base, at theThe placing of subtitles and their presentation Depth represented on the screen: a “scenic box” according to whether one is watching a mo- cost of a weaker 3-D effect, but the opposite The real depth and the depth represented creates too large left-right horizontal spa-on the air vie theater or television screen. on the screen in a 3Ds project are very dif- In a stereoscopic image, space is subdivi- cing so that the 3-D can no longer be fused,The placing of subtitles and graphic ferent things, and trying to show the actual ded into two volumes, one part in front of necessarily creating visual discomfort.elements in a 3-D television program So if the same film is projected on a larger dimensions of the subject on the screen is the screen and the other in back. Betweenis a technological and artistic feature a completely vain undertaking. The depth screen, the distance between the “homolo- large movie theaters and the living room ofthat must be taken into account before shown on the screen is called the “scenic the average man for example, this propor- gous” points of the “distant objects” (ele-the program is to be broadcast. It is re- box”. It obeys laws belonging to represen- tion between what is in front and what is in ments discernible the farthest towards infi-commended that scenarios should be tations in movie theaters or on a television back changes. nity) is going to increase quasi-proportionalbuilt for the placing of subtitles and/ and above all to the image shown (see dia- For all that, is it necessary to “calibrate” the to the base of the screen and thus go beyondor graphic elements based on an ana- grams below). 3-D according to the size of the television or the average inter-ocular distance of humanlysis of human perception so that they Nevertheless, one must be vigilant, becau- cinema screen? Is it necessary to adopt a beings (65 mm). se sharing foreground objects (popping-out median screen value for both these broad- The limit resides in the fact that the homo-do not interfere with the 3Ds effects in effects) and backgrounds (depths, distant cast vectors? Is it also necessary to take into logous points of objects located the farthestthe program’s scenes. Two options are objects) by specifying a precise position for account an “ideal” distance of the viewer in towards infinity on two stereoscopic imagespossible: either the subtitles are always the plane of convergence is only valid for a relation to the television screen? should not be more than 65 mm apart, oninserted in front of the video content given screen size. In particular, this plane pain of provoking ocular divergence in the One of the first basic rules consists in ca-(fixed depth positioning) and the rest of of convergence makes no sense with giant librating the 3-D of a TV program or a film viewer.the scene is sent to the background, or screens of the IMAX© type, for with them, according to the largest screen size abletheir position dynamically adapts to the all the represented volume can only be instereography of the program so that the theater itself. In fact, 6.5 cm on the basisthey are always in front of the content, of a screen of 30 m is so nonsensical that it Principle of the Floating Window is no longer taken into account (0.2%, thatwhile avoiding too great of a parallax is, 8 pixels out of an image of 4K). The im- The floating window is an arrangement of the stereoscopic image such that the windowbetween the scene and the text. portance and exact positioning of the plane is seen in front of the screen. It is obtained by the creation of a virtual screen frame that of convergence decrease steadily with the is closer to the viewer than the real screen frame in order to entirely or partially hide increase in the size of the screen. the violations of the stereoscopic window. Inversely, small screens are perfectly si- The floating window appears as black vertical bands on the left (in the left view) and tuated in terms of depth, and consequently on the right (in the right view), which reduces the horizontal visual field all the more a adapt to most of the image in back of the virtual frame close to the viewer is desired. The floating window can be dynamic and surface. This leads to a stereoscopic win- thus constantly change to adapt to the scene being broadcast. It is frequently used in dow that is more in front within the volume animation films. of the scenic box, just as during filming convergence would be made a little closer
    • 42 43 Relation between 3Ds parallax and the size of the screenThe CST, in collaboration with Alain Derobe, created a table establishing the average settings ofdistant objects viewed on different screen sizes: by percentage, fraction and screen discrepancies,measured in cm or in number of pixels of the 2K image.Experiments have been made on the rendering of distant objects for them to be as agreeable aspossible for an audience of spectators at common viewing distances.For example, if a film is calibrated for a screen of 10 m at its base, thus involving distant objectsoffset by a maximum 16 pixels, it will be necessary, aided by a general offset of the image, to reducethem by 10 pixels for a presentation valid for a screen of 26 m at its base; and inversely, to increasethe offset by 11 pixels to go to a screen of 4 m at its base. Explication du tableauExcept for small screens, the table is based on the viewpoint of an average spectator situated at adistance equal to the width of the screen for viewing a “normal” scene. So as an example, the first pro-ducers of television channels to broadcast in 3-D considered the size of an average television image tobe 42 inches with a viewing distance of about 3 meters.A true proportionality between the offset of distant objects and the size of the screen is only exact for a screen having Screen width (base) % offset Offset for distant objects Correspondence in pixels Screen of 26 m 0,25% 6,5 to 10 cm on the screen 5/7 pixels 2K or HD Screen of 19,5 m 0,33 % 6,5 to 9 cm on the screen 7/8 pixels 2K or HD Screen of 13 m 0,5% 6,5 to 8 cm on the screen 10/12 pixels 2K or HD Screen of 9,85 m 0,66 % 6,5 to 7 cm on the screen 15/16 pixels 2K or HD Sources : Alain Derobe-CST Janvier 2009 Screen of 6,5 m 1% 6,5 cm on the screen 20 pixels 2K or HD Screen of 5 m 1,1 % 5,6 to 6 cm on the screen 22 pixels 2K or HD Screen of 4 m 1,3 % 5 to 5,5 cm on the screen 27 pixels 2K or HD Screen of 3m 1,6 % 4,8 to 5,3 cm on the screen 32 pixels 2K or HD Screen of 2 m 2% 4 to 4,5 cm on the screen 40 pixels 2K or HD Screen of 1,5 m 2,25 % 3,4 to 4 cm on the screen 45 pixels 2K or HD Screen of 1 m 2,5 % 2,5 to 3 cm on the screen 50 pixels 2K or HD Screen of 65 cm 2,3 % 1,5 to 3 cm on the screen 45 pixels 2K or HD Screen of 50 cm 2,2 % 1 to 1,3 cm on the screen 42 pixels 2K or HD Screen of 30 cm 2,25% 6 millimeters on the screen 40 pixels 2K or HD Screen of 26 cm 2,3 % 5 millimeters on the screen 46 pixels 2K or HD Screen of 13 cm 2,5% 3 millimeters on the screen 50 pixels 2K or HDa base of around 6.5 meters. With larger screens, a bit larger offset of distant objects is possible, which will lead to adivergence of only a fraction of a degree, even for the first rows of a movie theater. For a screen larger than 6.5 me-ters at its base, another phenomenon comes into play: the synchrony that links convergence to the accommodationof the eyes. This phenomenon systematically goes against the effort of parallelism, which allows seeing beyond thesurface of the screen, so that the distant offsets are limited to a maximum of 2.5% of the image’s width.
    • 44 45 GLOSSARY 3Ds3-D professional monitoring directly depends on the size of the screen it Accommodation: Modification of the curvature Disparity: Distance between the homologous will be viewed on. of the lens of the eye due to the action of the points of the same object observed on theMonitoring on a small size screen is useful For example, on an editing monitor 1 me- muscles of the ciliary body in order to form images or the left and right retinas.for validating errors in producing simple 3-Deffects such as inversion of the left and right ter wide with the viewer at a distance of 2 a clear image on the retina of objects obser- Focusing: An operation that consists of meters, if the offset of the distant objects is ved at different distances. concentrating light rays coming from oneeyes, but it could never be used as a way ofappreciating 3-D in a feature film. adjusted from 40 to 50 pixels (2.5 %), the 3-D Angular disparity: See “Parallax angle”. point onto another point.All the graphic artists and technicians in image could seem pleasant to watch, but re- Automultiscopy: 3Ds visualization without Ghosts: “Ghosting”, perception of “cross-charge of an audiovisual and cinematogra- sult in a false setting according to the size of glasses with N viewpoints (N being greater talk” physical phenomena.phic project must be able to appropriate the screen that the public will finally view in than 2). Homologous points: The corresponding pointsstereoscopic production techniques and to a movie theater or a living room. It will then Autostereoscopy: 3Ds visualization without of the same object viewed by the left and ri-regularly view rushes of their work, in par- be impossible for the images to be fused for glasses, with two viewpoints. ght eyes, and whose distance between theticular during editing to adjust the 3-D and the eyes of a viewer who looks at a 13-meter Binocular rivalry: The perception of diffe- eyes displayed on the retinas constitutes thesolve “depth continuity” problems, which screen (50 pixels instead of 10 pixels recom- rences between the left and right views, in retinal disparity. These corresponding pointsresults in retakes of the framing. What mended in the table above represents five particular with geometric and colorimetric of the same object are also present on thewould thus be ideal would be to have a 3-D times the ideal inter-ocular distance, that is asymmetry. left and right images displayed on the planescreen available for each of the main pro- 32.5 cm on the screen). Convergence point: A point in space at the in- of the broadcast screen and whose distanceduction and postproduction stages in order However, it should be noted that the figures tersection of the optical axes of the eyes or between them constitutes the parallax.to be able to validate the advancement of on the table represent an observed average cameras that converge towards it. Horizontal shifting: The horizontal movementwork in progress. It is also indispensable to and depend on the quality of the restitution Convergence: Rotation of both eyes (binocular of stereoscopic cameras made parallel du-regularly test on “real-size” screens, that of the environment. Thus, a very good reso- convergence) or of two cameras, aiming at ring filming, or the displacement of two leftis, the same as those that viewers will be lution of a monitor allows the figures in the the same point in 3-D space. and right images in postproduction to set awatching, for here also the impact of 3-D table to be slightly exceeded. Cristalline lens: Biconvex lens of the eye, null parallax and thus recompose the depth behind the pupil, instrumental in the conver- of the scene. gence of light rays towards the retina on Horopter A virtual arc of a circle of a person’s which near or far observed objects are brou- visual environment formed by all the conver- ght to a focus. gence points coming from the observation of Crossed disparity: Retinal disparity corres- object-points located at the same distance ponding to the crossing of the optical rays of from the eyes. All the points situated on this each eye in front of the horopter or the plane curve correspond to identical places on each of convergence. retina. The retinal disparity is thus zero on Cross-talk: Imperfect physical dissociation of this curve. The disparity of objects observed images respectively intended for the left and inside the horopter is called “crossed dispa- right eyes during viewing of 3Ds content on a rity”, the disparity of objects situated outside plano-stereoscopic screen. is called “non-crossed disparity”. Depth range: The limits of the depth of 3Ds Hyperstereoscopy: Stereoscopy produced content coming from the left and right image from a wide stereoscopic base, usually well shots displayed on a screen or a stereosco- beyond the inter-ocular distance. pic projection. Infinite stereoscopy: The greatest distance Diopter A unit of homogenous vergence op- between the object and the viewer in bino- posite the length. cular vision where the effect of depth is still Diplopia: A disorder of vision characterized by discernible, usually estimated at 200 me- the absence of fusion of the image perceived ters. by each eye and provoking a double vision of Inter-axial distance: See “Stereoscopic base”. the observed object. Inter-ocular distance: The distance between
    • 46 47the pupils of each eye, generally considered and right images), and one sees with diplopia Retinal disparity: Disparity between homolo- binocular vision. It allows the creation of leftfor an adult male as being by default about vision. gous points of the same object formed on and right dual images and the perception of65 mm. Parallax angle: The angle starting from the the retina of each eye. 3-D when broadcasting.Keystone or trapezoid effect: The consequence of point of convergence observed by each eye Stereopsis: Sensation of depth given by bino- Vergence: The size characterizing the focu-a shot with two cameras in convergence. and forming a triangle with them. cular vision. sing properties of a system.Macrostereoscopy: Stereoscopy obtained from Parallax: The offset between the apparent Stereoscopic base: The distance between the Viewer: The observer, adult or child. Accor-a small stereoscopic base, below the intra- positions of an object due to the distance optical axes of two lenses of a single camera ding to the difference in their respective in-ocular distance, having virtually several mil- between the eyes of the observer. It is also or lenses of two cameras, with stereoscopic ter-ocular distances, adults and children dolimeters between each camera. the space between the left and right homolo- shooting. not have the same perception of 3-D depthMagnification factor: The relation between the gous points of the same object observed on a Stereoscopic binocular acuity: The depth reso- and do not feel the same sensations of visualrendered or captured image and the final size plano-stereoscopic screen. This space is due lution limit perceived by each eye. It repre- discomfort. It is thus necessary to take intoof this image on the broadcast screen. to the distance between the viewpoints of the sents the capacity to distinguish several account different distances to the screenMaquette effect: A 3-D effect where objects observed scene. planes of depth close to each other, planes (children closer to a 3Ds screen than adults),are perceived, during 3-D broadcasting, as Plane of convergence: When shooting in ste- defined by different parallax angles also a distance to be specified according to thebeing smaller than in real life. This sensation reoscopy, the “depth” plane that is determi- close together. left and right view separation technologyis due to the chosen size of the stereoscopic ned by making the homologous points of a Stereoscopic fusion: A phenomenon that com- specific to each type of 3Ds screen, and tobase. The cameras being separated beyond scene’s object coincide, and where the came- bines in the brain the views coming from verify the inter-ocular distance hypothesesthe inter-ocular distance, the real world is ras have their optical axes in parallel. The po- each eye, allowing the perception of one tri- taken into account by each manufacturer.perceived through the eyes of a giant and the sitioning is achieved by horizontal movement dimensional image. Zero parallax: A surface plane, physically re-humans observed appear as ants. of the two cameras or by horizontal shifting in Stereoscopic window: The 3Ds region of the presented by the broadcast screen, on whichMotion control stereoscopy: Usage of the left postproduction. image in three dimensions represented by are situated all the left and right homolo-and right cameras, especially to modify the Plano-stereoscopic screen: A screen from which the outer limits of the left and right views. gous points of the scene.stereoscopic base, convergence, focusing, the perception of 3-D depth comes from the A horizontal movement between these leftzoom, time synchronization, calibration of display of viewpoints for the left and right and right views modifies the position of theplacement, and so on. eyes on exactly the same planar surface of stereoscopic window in space.Negative parallax: 3-D objects perceived in front this screen. Stereoscopy: Principles and methods thatof the broadcast screen (for the retinal visual Plano-stereoscopic display: A display where 3-D allow the observation and/or restitution ofsystem, it is called “crossed disparity”. images intended for the left and right eyesNon-crossed disparity: Retinal disparity cor- form on the same surface of a screen.responding to the crossing of optical rays of Popping-out effect: When the stereoscopic win- APPENDIX 1: DEFINITION OF 3Ds PROFESSIONSeach eye in back of the horopter or the plane dow is shown on the plane of the screen, it Wof convergence. has to do with the 3-D effect in which objects ith the increase in 3-D experien- rections, the positioning of the plane ofOrthostereoscopy: The ideal position of the are seen in front of the physical broadcast ce of teams on filming sites or in convergence according to the editing beingviewer in relation to the broadcast screen, screen. It corresponds to a negative parallax. postproduction, as well as with the made, as well as the management of floa-where the 3-D image of the filmed objects Positive parallax: 3-D objects perceived in back continuous training courses in stereogra- ting windows.conforms to the real objects. The 3-D is per- of the broadcast screen (for the retinal visual phy for professionals, the stereographer It should be noted that the definition of 3-Dceived without depth distortion (flattened or system, it is called “non-crossed disparity”). will be increasingly less necessary for trai- management positions are different accor-stretched). Pseudoscopy: The inversion of the left and right ning everyone onsite. However, the stereo- ding to the genres (feature film, live broa-Panum’s fusional area: A virtual region situated images respectively intended for the left and grapher will remain the one who ensures dcasts or TV programs). The methodologyaround the horopter where the retinal dispa- right eyes. The left eye perceives the image the continuity of 3-D on a film or television and, above all, the teams will vary accordingrities can be fused by the visual system into a intended for the right eye (and vice-versa). program in relation with the entire team to the budget allocated to the production.tridimensional image. Outside of this region The 3-D is inversed and the objects normally working on a production. This is where the greatest difficulty lies: infusion is no longer possible, the images ap- situated in back of the scene are viewed in During postproduction, the stereographer making definitions of positions too defini-pearing doubled (in reality, the non-fused left front, which causes visual discomfort. also ensures the follow-up on 3-D cor- tive. In spite of all that, we are attached to
    • 48 49this exercise in order to better understand duction stages such as correcting conver- For live shooting: gineer deals with 3-D vision and with supervi-these new professions. gence errors, the continuity of depth in the sing the tools used for creating 3-D. He works shots, compositing, calibrating, correction under the direction of the stereographer and Stereographer is in charge of monitoring the angulation andOn stock TV and feature film programs: of disparities, etc. On streaming TV programs being shot in the inter-axial distance through the remote“Stereographer” or “Director of Stereography” 3Ds, the stereographer is usually employed control commands of 3-D assessment tools.On a feature film, the stereographer has for Stereographic technician on the same level as the director or the head When the means of production allow it, the He should not be confused with the traditio-the most part the role of “stereo-supervisor” of photography. He conceives the general stereographer can be assisted by a stereo- nal image vision engineer who ensures thewho determines with the director the “3-D stereographic options in collaboration with graphic technician in charge of physical control of the image in agreement with theshot” and the amplitude of the depth appro- the production and directing teams as well adjustments of, or the 3-D systems used, head of photography by acting on the came-priate for each sequence of the whole film. as the photography director and the chief ca- in shooting. He thus takes the initiative in ras’ commands (diaphragm, level of blacks,He also determines, with the photo direc- meraman (framing supervisor). He also par- setting up the rig and the camera, the ver- whites and gammas, corrections of detailstor, the most appropriate hardware for the ticipates, as outside personnel, in conceiving gence of the inter-axial distance and the and contours, matrices, etc.).shoot. On productions having a large budget the filming of shots and in the positioning ofand high artistic ambitions, the stereogra- involuntary disparity problems. When there the camera. He then supervises the workpher can be supported by a “stereographic are several teams shooting on a feature film of installing and adjusting the cameras and Stereographic techniciantechnician” dedicated to the operational ma- or several cameras on the same film set, the stereoscopic modules. He directs and super- In a large 3Ds multi-camera set-up (five to 6nagement of the 3Ds settings and monito- different stereographic technicians can ap- vises the work of the “convergence-pullers” rigs), there is generally a stereographer whoring as well as the 3Ds rushes. pear as generic “stereographers”, because (also sometimes called “assistant stereo- supervises all the filming, two 3-D visionThe stereographer must ensure the stereos- in this case they have much more autonomy graphers”) in order to obtain 3-D consistency engineers in the control room and a stereo-copic “guarantee of good end results” of a than in a usual shooting environment. between cameras. He also assists the pro- graphic technician per active rig (or for seve-production. The hierarchy remains unchan- duction in making choices that influence 3-D ral rigs). The vision engineer has a role veryged, but the stereographer is the same as a 3-D postproduction supervisor effects. At the stereographer’s side is some- near to the one he has in 2-D, except that indirector of special effects under the director times found one or several stereographic addition he must pair (match) both camerasand director of photography. The “3-D postproduction supervisor” belongs technicians who adjust the production rigs. on the same rig. It should be noted that tech-- With the director, he studies the stereosco- to the laboratory team. He is responsible for Also found there are 3-D vision engineers in nologies evolve very quickly in terms of 3-Dpic variations for the entire film. the adjustment of the settings of the digital the control room. filming and the convergence settings, regu-- With the chief operator, he studies the lat- postproduction machines. He will be working lated today by the stereographic technician,ter’s demands to guarantee that the tools hand-in-hand with the stereographer as well could in the end become operations that are 3-D vision engineer more and more automated.are used well and to respond to the specific as the editor and/or calibrator during 3-D ca- Based in the control room, the 3-D vision en-demands of the director of photography. He libration (depth grading). It also happens thatalso participates, as outside personnel, in the stereographer intervenes in a film as ahow the scenes are shot and in how the ca- “3-D supervisor” from one end to the other APPENDIX 2: 3-D FILMING TECHNIQUES :mera is positioned. He then supervises the of the production chain and thus takes on the From “Filming in Relief: the Complete and Interactive Course”, Parallell Cinemawork of installing and setting up the came- task of supervising the control of 3-D consis-ras and stereoscopic modules. Stereoscopic offset its right image to the right. In this case, the D tency at different stages of postproduction. It- For the production as a whole, he studies should be recalled that in postproduction it is e Stereoscopic offsets appear when object seems to be in the distance, behindthe necessary means for getting started in the image filmed by the right camera the plane of the screen, “in depth”. necessary to correct both “visual disparities”terms of teams and hardware. and the image filmed by the left ca- An offset is said to be null (0%) when the two (keystone, alignment, optical aberrations,- With all the production technicians, he mera are superimposed. The stereoscopic images of an object are perfectly superim- etc.) and to bring “corrections to stereoscopicanswers their precise questions on adapting offset of an object, or parallax, is the dis- posed. In this case, the object appears on settings” resulting from shooting errors, buttheir professions to 3-D. tance to the image between left and right the plane of the screen (exactly at the depth also from brutal 3-D variations introduced- With the manager of postproduction, he images of an object. It is expressed in the of projection screen). during editing by inverting shots planned forstudies the specific demands related to percentage of the width of the image, or in An offset is said to be negative (-1% for in the beginning.workflow. To ensure the consistency of all pixels: an offset is said to be positive when example) when the left image of an object isthe 3-D effects, he might supervise postpro- the left image of an object is to the left and to the right and its right image to the left. In
    • 50 51 will often be horrible on a screen of 13 m. They will give a weaker sensation of depth on a screen of 2 or 3 m. Adjusting the distant objects according to the planned screen size is thus very important from the beginning, even if it is possible to make adjustments in postproduction.Positive offset: the object seems Zero offset: the object seems on Zero offset: the object seems on • The artificial horizon of a 6.5 m screen is behind the screen the plane of the screen the plane of the screen thus +1% (the “+” meaning a positive offset). • The artificial horizon of a 13 m screen is +0.5%. • The artificial horizon of a 26 m screen is +0.25%. Effect of “angulation” or “vergence” on the The case where small screens are used is placement of the scenic box in relation to the eye, the eyes will look straight in front of plane of the screen them and be perfectly parallel in terms special: in fact, experience shows that the of view. majority of viewers tolerate more easily an On the other hand, if the two images on the screen are now offset 13 cm, then the left eye must look to the left and the right eye to the right: the viewing enters into divergence. Now this situation is not natural for the human eye, and at best it is tiring, or at worst painful, provoking nausea and headaches. It can thus be deduced that an offset (po-Adjustment of Distant objects in sitive) on the screen of 6.5 cm betweendistant objects divergence (diplopy) the two images of an object is the maxi-on an artificial horizon mum that we can tolerate. For this reason, this offset value is of- this case, the object seems near, in front of ten called the “artificial horizon”. It is the plane of the screen, “popping out”. An naturally a question of an absolute va- offset can be expressed, it should be noted, lue, which means that the same film is in percentage or in number of pixels. not necessarily adapted to every screen size. On a small screen (for example, 1 First step in shooting: adjusting distant objects m wide), if an offset is, for example, 1 cm One of the basic rules to be respected during (that is, 1% of the width of the image), shooting in 3-D is to ensure that the viewer it will be 13 cm when it is projected on will really have the sensation that an object a screen of 13 m. It will be 26 cm on an placed in the background of a scene is really IMAX© having a base of 26 m (see table positioned in the “depth” of the screen. For on page 44: the relation between the 3Ds example, the space existing between the parallax and the size of the screen). eyes is on average 6.5 cm for an adult male. Therefore, distant objects offset +1% of Therefore, if the image of a distant object the width of the image will be perfectly intended for the left eye is offset 6.5 cm in adapted to a screen of 6.5 m (since our relation to the image intended for the right +1% will make exactly 6.5 cm), but they Effect of inter-axial distance (distance between the optical axes of the cameras) on the stereoscopic range (amplitude of the scenic box)
    • 52 53artificial horizon situated between +1.8% and seems farther away. deformations of perspective in the angles of tant objects, the adjusting of the inter-axial+2.5%, the latter value already being quite This method is used to adapt the 3-D image the image, called “keystoning”. These de- distance will also allow the position of thelarge. Beyond this, the shot generally beco- to different screen sizes: an image is shifted formations, negligible in most shots, never- plane of the screen to be determined. Theremes too long to be superimposed. The artifi- in relation to another until distant objects theless require certain shots to be corrected exists several methods for determining thecial horizon of a small screen is thus around correspond to the artificial horizon of each in postproduction using morphing effects to inter-axial distance necessary according to+2% (with photos, the tolerance is greater be- screen size, that is: “make up for” the deformations of perspec- the scene being filmed.cause the image does not move). • About +2% for small screens tive, which otherwise would create visualIt should be noted that with negative offsets • +1% for 6.5 m screens fatigue. Method for determining the inter-axial distance by(that govern popping-out effects), no artificial • +0.5% for 13 m screens There exists two types of rigs: those that only calculating the stereoscopic rangehorizon really exists, convergence posing less • +0.25% for a 26 m IMAX© screen converge on one axis and those that conver- If the farthest object in the image has anproblems than divergence. However, it must While shooting, it is useful to determine the ge on both so as to apportion the trapezoid offset of +1% and the closest object has anbe kept in mind that an offset of -1% makes 3-D effect obtained by visualizing before- or “keystone” effect over both images. offset of -2%, then the stereoscopic range ofan object pop out at ½ the viewer’s distance hand the effect of the offset by using a 3-D The convergence of the cameras defines the this image is 3%, for +1-(-2)=3. Likewise, ifto the screen on a screen of 6.5 m, and at 2/3 monitor that allows an image to be shifted in plane of the screen and adjusts the distant the farthest object has an offset of +2% andthis distance on one of 13 m, a very strong ef- relation to another. objects. It is necessary to locate the most the nearest an offset of 0%, the stereoscopicfect. distant object in the scene on a 3-D monitor range of the image is 2%, for 2-0=2. Filming with convergence and to angle a camera until both images of For small screens, a stereoscopic range ofFilming in strict parallel t Another method exists for adjusting distant this object have the desired offset: for exam- 1.5% to 3% is often recommended. For lar-Filming in strict parallel, without angulation objects, which is preferred by certain stereo- ple, +1%. ger screens, smaller stereoscopic rangesor offset of an image in relation to another graphers because it avoids the loss of a band are usually recommended: 0.75% to 1.5%.one in postproduction, hardly takes place of several pixels on the left and right of the Second step: adjust the inter-axial distance Of course, the exact stereoscopic rangeanymore except in IMAX© format, where it image when an image is shifted in relation to The inter-axial distance is often adjusted depends on each shot and the effect oneadapts well. For all smaller screens (cine- another in postproduction. Rather than shift once the distant objects have been set. The wishes to obtain. For certain shots (popping-ma, television), this type of filming generally or offset an image in relation to another, a inter-axial distance is the distance separa- out effects, for example), one might want togives disappointing results, since it is cha- camera, or both, can be angled, that is, to ting the centers of each camera’s lens. This precisely control the stereoscopic range.racterized by the absence of positive offsets: have them make a small panorama of less should not be confused with the inter-ocular Starting from an inter-axial distance of 0everything is popping out, nothing is behind than one degree, which is also called the distance separating the optical axes of the cm, first the distant objects are set by usingthe screen and distant objects are on the vergence of the cameras. eyes (6.5 cm on average). The inter-ocular angulation (for example, +1%). Then the in-plane of the screen. When a camera is angled, a small panorama and inter-axial distances are independent, ter-axial distance is progressively increasedIn strict parallel, without postproduction off- is made. Now, unlike a travelling, in a pano- the inter-axial distance being used to adjust until the left and right images of the closestsets or angulation, as soon as a film is looked rama the perspective does not change. the “stereoscopic range” of an image, which object reach the value of the desired stereos-at on a screen smaller than that of IMAX©, Mathematically, it is the same thing as a also depends on the focal length and the po- copic offset. This is directly controlled on thepopping out effects are not very comfortable postproduction offset (shift): with an angu- sitioning of the first and last object. 3Ds monitor (in our example, the inter-axialdue to the proximity of the screen, which for- lation, like in a postproduction offset, all the The inter-axial distance varies according to distance would be increased until a value ofces the eyes to take quite large convergence pixels of the image are shifted to the left or the shots: when a large inter-axial distance -2% is reached for the closest object if a ste-angles. to the right. This is why filming in parallel is needed (landscape shots, miniaturization reoscopic range of 3% is desired). with postproduction offset and filming with effects), rigs are used side-by-side. But the- But another method can be used that hasFilming in parallel with offsets in postproduction convergence are mathematically equiva- se do not allow the cameras to get very close. the advantage of not needing a 3Ds monitor lent—even if the two methods have practical When small inter-axial distances are needed thanks to the following formula:(“shift”) differences (keystone problems or loss of (for most shots), mirror rigs are used.For this reason, on screens smaller than pixels on the left and right of the image). As the inter-axial distance is used to adjust LxG=EIMAX©, it is necessary to offset (“shift”) an When filming with convergence, since one the stereoscopic range, it is set according to where:image in relation to another one to create camera is angled, in reality one camera the scene in order to obtain the stereoscopic L is the width (in meters) of the frame at thepositive offsets: this pushes all the 3-D in films a rectangle and the other, by compari- range desired. But since the vergence of the level of the closest object (measured on thea single block towards the back without son, a trapezoid. Thus are introduced slight cameras was set to define the offset of dis- set, for example: 1.5 m).touching the amount of depth; everything
    • 54 55G is the stereoscopic range desired in percent position of the plane of the screen is the most(for example: 2%) important parameter. This allows, among mains beneficial for the operator, since a sin- Side-by-SideE is the inter-axial distance in centimeters. other things, to avoid irritating window er- gle channel is enough to broadcast 2-D andFor example:1.5 x 2% = 3 cm rors. 3Ds images. But the necessity of a different Once the distant objects are set through an- grammar makes editorial compatibility so- gulation, the inter-axial distance is progres- mewhat delicate (axes and settings of theMethod for determining the inter-axial distance by shots, rhythm of editing, etc.). New produc- sively increased until the plane of the screenpositioning the plane of the screen (that is, objects having an offset of 0%) is pla- tion methods need therefore to be inventedFor other shots, where the stereoscopic ran- ced where one wants. in order to optimize the technical capabilities,ge does not reach critical values, the precise all the while guaranteeing the artistic quality of the 2-D and 3Ds versions of the same pro- gram. APPENDIX 3: CODECS AND DISTRIBUTION MODES T wo major technological families can be Frame Compatible modes of distribution distinguished that allow stereoscopic The main principle of the Frame Compatible modes is to reduce the resolution of the left The left and right views are made anamorphic content to be broadcast. The first, called and right images by half in order to group and placed side by side. This method induces “Frame Compatible”, has the advantage that them in one and the same HD image. This a theoretical horizontal loss of definition of it can be used on existing broadcast networks. spatial compression (horizontal or vertical 50% for each eye, but the work done by the This technology spatially compresses the left anamorphosis) generates a 2-D signal that brain to recreate the sensation of 3-D usually and right views into a single image, but has can be processed and transmitted by existing attenuates this loss of real definition. the inconvenience of reducing by half the ori- ginal resolution. Furthermore, a Frame Com- equipment. patible image appears as two anamorphic During decoding, each of these two views is Top-and-Bottom Horizontal decimation images placed one beside the other, thus ma- (one pixel out of two is kept on each line) made “deanamorphic” and displayed on the king the operator broadcast the 2-D version of screen in order to recreate the sensation of the same program on a separate channel. 3-D. To compose a Frame Compatible image, As for the “Service Compatible” mode, it al- it is first necessary to select those pixels lows one and the same signal to be broadcast to be retained in the left and right original to all receivers. Using this type of approach, views. This step is called “decimation” and 2-D televisions only use that part of the signal there exists several ways of proceeding: one that they need, but the 3Ds models are capa- can choose to only retain one pixel out of two ble of displaying the left and right views in full on each line, in each column or in staggered definition. rows. Moreover, the position of the retained Whatever the method being considered, the pixels can be identical for both images, or Vertical decimation broadcast of a 3Ds signal requires a band- (one pixel out of two is kept in each column) else offset (by one line or one column). width much greater that its monoscopic Once the pixels to be retained have been se- The left and right views are made anamor- equivalent. The Frame Compatible modes ge- lected in both views, then the way to arrange phic and placed one above the other. This nerally require between 15% to 35% supple- them within one and the same image must method induces a theoretical vertical loss of mentary throughput because of the increase be determined, which is called “packing”. definition of 50% for each eye, but, as for the in high frequencies in the image that solicits Here again, several solutions exist: Side-by- Side-by-Side mode, the visual discomfort felt the encoders more. Side, Top-and-Bottom, Checkerboard, etc. by the viewer is not necessarily very great. As for the Service Compatible modes of distri- Although it is theoretically possible to choo- bution, they require an even higher through- se different decimation packing modes, it is Line-by-Line put, in the order of 50% to 70% in comparison generally understood that these two steps In this system, the lines coming from one with the 2-D version. From a strictly technical Decimation in staggered rows follow a certain logic. eye are placed on the even lines of the final point of view, this increase of throughput re- (checkerboard sampling)
    • 56 57image and those coming from the other eye tical decimation.on the odd lines. The “Line-by-Line” mode is However, the Checkerboard mode is not atnot very well adapted to video compression all adapted to video compression and willbecause its structure solicits the encoders practically never be used such as it is formore, and it works badly with color sub- broadcasting. On the other hand, decimationsampling (4:2:0). by Checkerboard associated with Side-by- subtitle placed too near on a very deep bac- ther form of backward compatibility: it allows Side packing has been shown to be a very kground. The standard allows this background full resolution 3Ds programs to be broadcastCheckerboard efficient method for spatial compression to be managed differently according to the re- while remaining readable by a DVB-3D PhaseEach source image is sampled according to (Sensio proprietary codec, for example).at gion of the image where the subtitles become 1 decoder. The principle here is to transmita checkerboard structure and in a comple- the international level, but companies such as inserted. a Frame Compatible image accompanied by Dolby and Sensio are already proposing pro- supplementary information that allows thementary way for each view. The loss of defi- prietary methods. DVB-3DTV Phase 2 left and right views to be displayed in their fullnition felt is less than with horizontal or ver- Les normes DVB-3DTV phase2 sont encore resolution. With this system, the first-genera- eThe DVB-3DTV Phase 2 standards are still tion 3Ds decoders will process the 3-D images being developed. They will permit a Service in half resolution per eye, whereas the new DVB BROADCASTING IN 3Ds Compatible approach, that is, backward com- decoders will be capable of interpreting the The standard describes the transmission of improvement layer and to reproduce the native signaling information that allows the decoder patible with older television receivers: - DVB-3DTV Phase 2a, whose specifications definition of the original images. The improve-DVB-3DTV phase 1 to know which type of Frame Compatible it is ment layer transports, in fact, the spatial in-The DVB European consortium, which propo- receiving, and thus to choose the appropriate should appear in the summer of 2012, will allow TV viewers equipped with a 2-D screen formation not present in the base layer. Takingses TV broadcasting standards, defined 3Ds processing. This information is conveyed in the into account the strong correlation betweenTV broadcasting modes in Frame Compatible SI (Service Information) tables of the DVB sys- to watch programs broadcast in 3Ds. This is done by broadcasting the left image plus an these two streams of data, the improvementformat in February 2011. This broadcasting tem as well as in the MPEG elementary packets. layer proves to be very light (in the order ofcan thus take place from now on using existing It has been planned that a channel can broad- improvement layer which will only be decoded for 3-D screens. The 2-D televisions will not 10% of the base layer in current encoders).HD infrastructures that make use of DVB stan- cast 2-D at certain moments and 3Ds at others: This approach has not yet been standardizeddards. in this case, the 2-D commutation to 3Ds and decode this and will only display the left eye. The MVC codec can no doubt be used for this. at the international level, but companies suchThis standard recommends H264 compression inversely can be automatically generated by as Dolby and Sensio are already proposingas well as the use of the following display for- the decoder. Likewise, the electronic program Even so, this technique does not settle all pro- duction problems: a production planned for proprietary methods.mats: guide (EPG) will be able to say which programs are in 3Ds. The standard foresees the dynamic 3Ds could turn out to be bad in 2-D. management of subtitle and graphics paral- - DVB-3DTV Phase 2b corresponds to ano-Side by side Top and Bottom1080i/25 720p/50 lax so as to avoid conflicts of depth indications1080i/29.97 720p/59.94 (a subtitle placed farther away than an object1080i/30 720p/60 that it is hiding). This also allows visual fatigue 1080p/23.98 to be avoided caused by the juxtaposition of a
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