Police photography


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Police photography

  1. 1. POLICE PHOTOGRAPHY REVIEW NOTES A.Photography 1. Literal Definition: The word photography us derivative of two Greek words; phos which means “light” and graphia meaning “write”. Therefore photography best translates to “write with light”. (Herschel 1839) 2. Modern definition: Photography is an art or science which deals of the reproduction of images through the action of light Upon sensitized materials, with the aid of camera and its accessories and the chemical processes involved therein. (Aquino 1972) 3. Technical/Legal Definition: Modern photography may be defined as any means for the chemical, thermal, electrical or electronic recording of the images of scenes, or objects formed by some type of radiant energy, including gamma rays, x-rays, ultra violet rays, visible light and infrared rays. This definition is broad enough to include not only the conventional methods of photography but almost and new process that may developed. (Scott 1972) PRINCIPLES OF PHOTOGRAPHY: A photograph is both mechanical and chemical result of photography. To produce a photograph, light is needed aside from sensitized materials (film or paper) Light radiated of reflected by the subject must reach the film while all other lights are excluded. The exclusion of all other lights is achieved by placing the film inside a light tight box (camera).
  2. 2. The effect of light on the film is not visible in the formation of images of objects. To make it visible, we need or require a chemical processing of the exposed film called development. The visual effect of light on the film after development varies with the quantity or quality of light that reached the emulsion of the film. Too great in the amount of light will produce a transparent or white shade after development. The amount of light reaching the film is dependent upon several factors like lightning condition, lens opening used, shutter speed used, filters used, etc. B) Police Photography Is an art or science which deals with the study of the principles of photography, the preparation of photographic evidence, and its application to police work. (Aquino 1972) C) Forensic Photography Is the art or science of photographically documenting a crime scene and evidence for laboratory examination and analysis for purposes of court trial. HISTORICAL EVOLUTION OF FORENSIC PHOTOGRAPHY A.The Basic components Of Photography 1. Light 2. Equipment 3. Chemicals B.True Photography  1839-is generally known as a birth year of photography. William Henry Fox Tablot explained a process he had invented (calotype) at a royal society of London.
  3. 3. The “Calotype” used paper with its surface fibers impregnated with light sensitive compounds.  Louis Jacques Mande Daguerre- made a public demonstration in Paris. The Daguerriotype in collaboration to Joseph Nicephore Niepce.  The Daguerreotype formed an image directly on the silver surface of a metal plate.  With Talbots CALOTYPE the fixation was only partial while the daguerreotype image were permanent with the use of hypo.  1848 – Abel Niepce de Saint Victor introduced a process of negatives. Important Personalities in Police Photography *Joseph Nicephore Niepce - was able to obtain camera images on papers sensitized with silver chloride solution in 1816.He invented a photographic process which he called "heliography" meaning "writing of the sun" *Louis Jacques Mande Daguerre - invented "Daguerreotype", an early photograph produced on a silver or silver-covered copper plate.It formed an image directly on the silver surface of a metal plate.It was a positive process,thus,it yielded one of a kind images. *William Henry Fox Talbot - invented a process called calotype, a photographic process by which a large number of prints could be
  4. 4. produced from a paper negative.Calotype use paper with surface fibers impregnated with light sensitive compounds. Calotype vs. Daguerre - fixation in calotype was only partial while images in daguerreotype were made permanent with the use of hypo (short for hyposulfite thiosulfate,sodium thiosulfate or a solution of thiosulfate). Sodium thiosulfate or hypo is a hygroscopic (readily taken up and retaining moisture) crystalline salt used especially as a photographic fixing agent and a reducing or bleaching agent. *John Frederick William Herchel - coined the term photography and applied the terms negative and positive to photography.He made improvements in photographic processes, particularly in inventing the cyanotype process and variations (such as the chrysotype) the precursors of the modern blueprint process. - He discovered sodium thiosulfate to be a solvent of silver halides in 1819, and informed Talbot and Daguerre of his discovery that this "hyposulfite of soda" (hypo) could be used as a photographic fixer, to fix pictures and make them permanent after experimentally applying it in 1839. *Richard Leach Maddox - was an English photographer and physician who invented light weight gelatin negative plates for photography in 1871. *Frederick Scott Archer - invented the photographic collodion process which preceded the modern gelatin emulsion. Collodion - is a wound dressing material made of nitrated cotton
  5. 5. dissolved in ether and alcohol and other chemicals on sheet of glass. *George Eastman - founded the Eastman Kodak company and invented roll film, helping bring photography to the mainstream. Definition of Terms: Photography - To write with light,from two Greek words, Phos - light and Graphia - write. Police Photography - It is an art or science which deals with the study of the principles of photography, the reproduction of photographic evidence, and its application to police work. Forensic Photography - the art or science of photographically documenting a crime scene and evidence for laboratory examination and analysis for purposes of court trial. 1.Take photographs of the following: a.crime scene b.suspects. c.detainees d.prisoners e.aliens f.apprehended persons g.applicants for clearances
  6. 6. h.military and civilian personnel i.unknown cadaver j.applicant to possess firearm k.other physical evidence 2. Conduct comparative examination and analysis of questioned photographs or pictures to the known photographs. 3. Process color and black and white film, print, reduce and enlarge picture. 4. Reproduce picture and other printed matters. 5. Compose portrait by means of portrait composition. 6. Provides photographic intrusion detection devices. 7. Maintain Rogues Gallery (a collection of pictures of persons arrested as criminals) Care and Handling of Camera - Must be carried using a portable bag or built-in container to avoid dust and dirt. - Must be kept dry and avoided contact with water and other liquid substances. - Must be repaired only by qualified technician. - Must not be cleaned by oil. - Must not be fixed without proper equipment and tools to avoid serious damage on it.
  7. 7. Basic Camera Parts and Functions Camera is a light-tight box; with a lens to form an image with a shutter and diaphragm to control the entry of the image; a means of holding a film to record the image/and a viewer or viewfinder to show the photographer what the image is. Camera originated from the term camera obscura. Camera obscura (Latin veiled chamber ) is an optical device used, for example, in drawing or for entertainment. It is one of the inventions leading to photography. The principle can be demonstrated with a box with a hole in one side (the box may be room-sized, or hangar sized). Light from a scene passes through the hole and strikes a surface where it is reproduced, in color, and upside-down. The image's perspective is accurate. The image can be projected onto paper, which when traced can produce a highly accurate representation. 1. Light Tight Box. This part of the camera is very essential because of its capability to exclude all unwanted light that may expose the sensitized materials or film. It is an enclosure that is devoid of light. 2. Lens. The lens is the only responsible in focusing the rays of light coming from the subject. It is one of the most important parts of camera because without lens, it is impossible to form a sharp image of the film. 3. Film H older. The film holder holds the film firmly inside the camera. It
  8. 8. is always located at the opposite side of the lens of the camera. 4.Shutter. The shutter served as the barriers of the rays of light that will enter and effect the film inside the camera. It is usually placed at the path of the light passing thru the lens. Other Parts of the Camera 1. Viewing system 2. Film advancer 3. Shutter speed 4. Lens aperture 5. Focusing mechanism Major Types of Camera 1.View Finder Type - The smallest and simplest type of camera. This is also known as instamatic camera. View finder camera suffers parallax error. 2.Single Lens Reflex Type - Cross section view of SLR system 1) Lens 2) Mirror 3) Shutter 4) Film or sensor 5) Focusing screen 6) Condensing lens 7) Pentaprism
  9. 9. 8) Eye piece The best way to determine the entire coverage of the camera is to look behind the lens of the camera. In this manner the object can be framed properly and recorded on the film. This type of camera eliminates the problem of parallax error. Twin Lens Reflex Camera - has two lenses, one for viewing and focusing on the subject and for taking lens. In this type of camera, the image to be photographed is seen as flat surface as the image is reflected by the mirror behind the viewing lens. This suffers parallax error. Parallax - the difference between what the view finder on a point and shoot camera sees and what the lens sees (and thus records on film).At close shooting distances, the difference can cause you to crop off the top of a subject's head. Parallax error - the image you see through the view finder is different from the image the lens will capture. VIEW OR PRESS TYPE 1.Lens plane 2.Front standard 3.Lens axis 4.Base
  10. 10. 5.Film holder/Ground glass 6.Rear standard 7.Film plane View Or Press Type Camera - The biggest and most sophisticated among the different type of camera. This type of camera is practically useless for candid and action photography. Special Cameras - These are cameras that have been devised that offer unique advantage or serve special purposes. Among the special cameras are: a. polaroid, b. panoramic cameras, c. aerial cameras, d. miniature and ultra-miniature cameras e. digital cameras (using computer processing. Control of Cameras: Knowing the controls on camera is necessary to produce a sharp and normal image and negatives after photographing. There are three important controls in a camera to be manipulated and adjusted to its proper setting. * Focusing control * Diaphragm/Aperture control * Shutter speed Focusing Control - The camera lens bends light rays to form an image or likeness of the object. Adjusting the lens to form the clearest possible image is called
  11. 11. focusing. Focusing is defined as the setting of the proper distance in order to form a sharp image. Three Types of Focusing 1.Rangefinder Type (e.g. viewfinder, instamatic camera and 35mm cameras) 2.Ground Glass Type (e.g. twin-lens reflex camera and digital camera) 3.Scale Bed Type (e.g. press and view camera, and Polaroid Evidence Camera) Rangefinder Type The rangefinder type is classified into two: 1. Coincidence type - the object to be photographed looks double when the focusing control is not in proper distance, and by moving this control, one of the objects will move and coincide with the other object to make as one and become accurate appearance of an object. 2. Split Type - Splits the objects to be photographed into two. While moving the focusing control, the split image will move and unite to form an undivided appearance and therefore the focus is accurate and perfect. Ground Glass Type Ground glass type focusing mechanism clearly indicates whether the object distance and the camera is out of focus or not. If the object is not well focused, the object to be photographed will appear blurred. To
  12. 12. make it clear and accurate the focusing ring of the camera is adjusted on clockwise or counter clockwise to get the desired clearness of the object. Scale-Bed or Focusing Scale In the scale or bed type focusing mechanism, the distance of the object to be photographed is calculated by means of feet or meter. There are cameras where estimated distance from the camera to objects is being indicated in the focusing ring. Diaphragm Control (lens opening) A device called a diaphragm usually serves as the aperture stop, and controls the aperture. The diaphragm functions much like the iris of the eye²it controls the effective diameter of the lens opening. Reducing the aperture size increases the depth of field, which describes the extent to which subject matter lying closer than or farther from the actual plane of focus appears to be in focus. Aperture and shutter speed are the fundamental controls available to the SLR user: Varying one or other of these opens up a myriad of creative possibilities. Both also control how much light reaches the film ± so if you make the hole through which the light passes into the camera (the aperture) smaller; you must keep this hole open for longer (the shutter speed) to compensate. Fortunately, on most cameras this adjustment is made automatically. The size of the aperture is measured using f/numbers (or f/stops). Confusingly, as f/numbers represent fractions, the larger the f/number the smaller the aperture. The widest aperture on a lens might be f/2, whilst the smallest aperture available may be f/22. Shutter Speed - is a device that allows light to pass for a determined period of time, for the purpose of exposing photographic film or a
  13. 13. light-sensitive electronic sensor to light to capture a permanent image of a scene. Types of Shutter 1. Central shutters 2. Focal-plane Central Shutters - are mounted within a lens assembly, or more rarely behind or even in front of a lens, and shut off the beam of light where it is narrow. A leaf mechanism is usually used. Focal Plane Shutter - In camera design, a focal-plane shutter is a type of photographic shutter that is positioned immediately in front of the focal plane of the camera, that is, right in front of the photographic film or image sensor. Types of Shutters (as to mechanism) 1.Focal-plane shutters 2.Leaf shutters 3.Diaphragm shutters 4.Central shutters Focal-Plane Shutters - Focal-plane shutters are usually implemented as a pair of cloth, metal, or plastic curtains which shield the film from light. Leaf Shutters - is a type of camera shutter consisting of a mechanism with one or more pivoting metal leaves which normally does not allow light through the lens onto the film, but which when triggered opens the shutter by moving the leaves to uncover the lens for the required time to make an exposure, then shuts. Diaphragm Shutters - is a type of leaf shutter consisting of a number of thin blades which briefly uncover the camera aperture to make the
  14. 14. exposure. Central Shutters - is a camera shutter normally located within the lens assembly where a relatively small opening allows light to cover the entire image. The term is also used for shutters behind, but near to, the lens. Interchangeable lens cameras with a central shutter within the lens body require that each lens has a shutter built into it. In practice most cameras with interchangeable lenses use a single focal plane shutter in the camera body for all lenses, while cameras with a fixed lens use a central shutter. In photography, shutter speed is a common term used to discuss exposure time, the effective length of time a shutter is open; the total exposure is proportional to this exposure time, or duration of light reaching the film or image sensor. There are many factors to be considered in using this control . Some of these factors are: 1.The light sensitivity of the film, which are determined through its ISO 2.The lighting condition 3.The motion of the subjects on different angles 4.The purpose of the photographs to be taken, etc. The different shutter speeds are: 1, 2 or 1/2 sec, 4 or 1/4 sec, 8 or 1/8 sec, 15 or 1/15 sec, 30 or 1/30 sec, 60 o r 1/60 sec, 125 or 1/125 sec,250 or 1/250, 500 or 1/500 sec, 1000 or 1/1000, 2000 or 1/2000. Camera shutters often include one or two other settings for making very long exposures: B (for bulb ) - keep the shutter open as long as the shutter release is held. T (for time ) - keep the shutter open until the shutter release is pressed again. Avoiding Camera Shake
  15. 15. Unless you are using a tripod, the first thing you should ensure when choosing the shutter speed is that it is fast enough to avoid camera shake. However tightly you hold your camera, it will always move slightly as you fire. If you use too slow a shutter speed this will mean blurred pictures. The speed you use depends on the focal length of lens you are doing. How to Hold Your Camera To be able to use the slowest possible handheld speeds, you must hold the camera correctly to avoid as much vibration as possible. Low-level shooting - you don’t always want to take your pictures from normal eye level. This kneeling position allows you to take shots at waist level. When to Use Slow Shutter Speeds - By using a tripod, or other camera support, photographers can use slower shutter speeds than usual. These allow you to use apertures that would not otherwise be possible when using a handheld camera and to shoot in the lowest light. Slow shutter speeds can also be used for creative effect, as moving subjects will become artistically blurred. When to Use Fast Shutter Speeds Moving subjects require you to consider using a faster shutter speed than that needed to avoid camera shake. Some blur may be welcome with action subjects, but often we want to freeze the action. Selecting the right shutter speed depends not only on the velocity of the subject,
  16. 16. but also on the direction in which it is traveling. The Lens - A lens is an optical device with perfect or approximate axial symmetry which transmits and refracts light, converging or diverging the beam. Types of Lenses 1. Biconvex 2. Biconcave 3. Plano-convex/plane-concave 4. Convex-concave or meniscus 5. Positive or converging lens 6. Negative or diverging lens Biconvex - A lens is biconvex (or double convex , or just convex ) if both surfaces are convex. Biconcave - A lens with two concave surfaces is biconcave (or just concave ).
  17. 17. Plano-convex or Plano-concave - If one of the surfaces is flat, the lens is plano-convex or plano-concave depending on the curvature of the other surface. Meniscus - A lens with one convex and one concave side is convex- concave or meniscus.It is this type of lens that is most commonly used in corrective lenses. Positive or Converging Lens - If the lens is biconvex or plano-convex, a collimated or parallel beam of light traveling parallel to the lens axis and passing through the lens will be converged (or focused ) to a spot on the axis, at a certain distance behind the lens (known as the focal length ). In this case, the lens is called a positive or converging lens. This lens is always thicker at the center and thinner at the sides. Light passing through it is bended toward each other on the other side of the lens meeting at a point. It produces a real image on the opposite side of the lens or where light is coming from. Negative or Diverging Lens - If the lens is biconcave or plano- concave, a collimated beam of light passing through the lens is diverged(spread); the lens is thus called a negative or diverging lens. The beam after passing through the lens appears to be emanating from a particular point on the axis in front of the lens; the distance from this point to the lens is also known as the focal length, although it is negative with respect to the focal length of a converging lens.This lens is always thinner at the center and thicker at the sides. Light passing through it is bended away from each other as if coming from a point. It
  18. 18. produces a virtual image on the same side of the lens or where light is coming from. Inherent Lens Defects or Aberrations 1. Spherical Aberration 2. Coma 3. Curvature of Field 4. Distortion 5. Chromatic Aberration 6. Astigmatism 7. Chromatic Difference of Magnification Spherical Aberration - When light passing through near the central part of a converging lens is bended more sharply than those rays falling in the edge, thus the rays coming from the edges are focused on a plane nearer the lens than those coming from the central part. Coma - This is another form of spherical aberration but is concerned with the light rays entering the lens obliquely. The defect is noticeable only on the outer edges and not on the central part of the lens. If a lens has coma, circular objects reproduced at the corners of the negative are comet-like form. Just like the spherical aberration, it is reduced by combinations of lenses of different curvatures. Curvature of Field - This is a kind of defect where the image formed by a lens comes to a sharper focus in curved surface than a flat surface.
  19. 19. The correction of this defect is similar to spherical aberration and coma. Distortion - A lens with distortion is incapable of rendering straight lines correctly; either horizontal or vertical lines in an object. This is caused by the placement of the diaphragm. If the diaphragm is placed in front of the lens,straight lines near the edges of the object tends to bulge outside. This is known as the barrel distortion.If the diaphragm is placed behind the lens, straight lines near the edges tends to bend inward. This isknown as the pincushion distortion. Distortion is remedied by placing the diaphragm in between the lens component and the two opposite distortions will neutralize each other. Chromatic Aberration - This defect is the inability of the lens to bring photographic rays of different wavelengths to the same focus. Ultraviolet rays are bent the most while infrared rays are bent to the least when they pass through the lens. This defect is reduced by utilizing compound lenses made up of single lens made up of glass of different curvatures. Astigmatism - This defect is present when the size of image produced by photographic rays of one wavelength is different from the size produced by another. Size of the image increases as the wavelength of the rays decreases. In color photography it produces a rainbow colored fringes around the edges of objects while in black and white photography, it appears as a slight blue.
  20. 20. Types of Lenses (as to degree of correction to lens aberration) 1. Achromatic lens - corrected for chromatic aberration. 2. Rapid-rectilinear lens - corrected for distortion. 3. Anastigmatic lens - corrected for astigmatism as well as the other lens defects. 4. Apochromatic lens - also corrected for astigmatism but with higher degree of correction to color. Focal length - is the distance measured from the optical center of the lens to the film plane when the lens is set or focused at infinity position or far distance. Focal length is a measure of the light-bending power of a lens. It is invariably measured in millimeters (mm). The longer the focal length of a lens, the narrower the angle of view , and the larger objects appear in the viewfinder without the need to move any closer to them. Focal Distance - is the distance from the optical center of the lens to the film plane. Telephotos - are long focal length lenses. Telephotos are lenses with focal lengths greater than 50mm. They range from 70mm short telephotos to "long toms" with focal lengths of 1000mm or more. Wide angles - are short focal lengths. A lens with a focal length of 50mm is known as a standard lens ± the
  21. 21. view that it gives is similar to that of the human eye . Any lens with a shorter focal length, and wider angle of view, is known as wide-angle. How Focal Length Affects Image Size - Lenses work on the principle that light affecting from a subject can be bent using the refractive properties of glass to form a miniature image of the subject. Lenses with short focal lengths, such as the wide-angle lens, produce a small image. Telephoto lenses, with longer focal lengths, produce a larger image, when taken from the same distance. Zoom Lens - It is a kind of lens with variable focal length. Does Focal Length Affect Depth of Field? Aperture is not the only factor that affects how much of a scene is in focus. You should also take into account the focal length of the lens being used and the distance that the lens is focused at (generally the distance from the camera to your subject). The longer the focal length, the more restricted depth of field becomes.So, all things being equal, a wide-angle lens keeps more of the scene in focus than a telephoto one. In addition, depth of field becomes increasingly more limited the closer you are to the subject that your lens is focused on. Factors Affecting Depth of Field 1. Aperture - The larger the aperture the less depth of field. For maximum depth of field, use the smallest aperture. 2. Focused Distance - The closer the subject you focus on, the less depth
  22. 22. of field. Depth of field is greater with distance subjects. 3.vFocal Length - The longer the lens you use, the less depth of field you will have. Wide-angle lenses give the greatest depth of field. Films and Papers A.Black and White Films 1.Emulsion - a suspension of a sensitive silver salt or a mixture of silver halides in a viscous medium (as a gelatin solution) forming a coating on photographic plates, film, or paper. 2. Gray or Anti-Halation Backing - a layer found in modern photographic films. It is placed between the light-sensitive emulsion and the tough film base, or sometimes on the back of the film base. The light that passes through the emulsion and the base is absorbed by the opaque anti-halation layer. This keeps that light from reflecting off the pressure plate or anything else behind the film and re- exposing the emulsion, reducing contrast. The anti-halation layer is rendered transparent or washed from the film (as in K-14 films) during processing of the film. 3.Film Base- A film base is a transparent substrate which acts as a
  23. 23. support medium for the photosensitive emulsion that lies atop it. Despite the numerous layers and coatings associated with the emulsion layer, the base generally accounts for the vast majority of the thickness of any given film stock. Historically there have been three major types of film base in use: cellulose nitrate,cellulose acetate (cellulose diacetate, cellulose acetate propionate, cellulose acetate butyrate, andcellulose triacetate), and polyethylene trephthalate polyester (Kodak trade-name: ESTAR). Characteristics of B & W Films: 1.Emulsion Speed 2.Spectral Sensitivity 3.Granularity or Graininess Emulsion Speed a. ASA (American Standards Association) rating. This is expressed in arithmetical value. b. DIN (Deutsche Industrie Normen) rating, which is expressed in logarithmic value. c. ISO (International Standards Organization) rating. This is expressed in the combined arithmetical and logarithmic values. Spectral Sensitivity a. Blue sensitive film ± sensitive to UV rays and blue color only b. Orthochromatic film ± sensitive to UV rays, to blue and green color.
  24. 24. It is not sensitive to red color. c. Panchromatic film ± sensitive to UV radiation to blue, green, and red light or all colors. d. Infra-red film ± sensitive to UV rays, to blue, green, red light and infrared rays. Granularity or Graininess - This refers to the size of the metallic silver grains that are formed after development of an exposed film. Generally, the size of metallic silver grains are dependent on the emulsion speed of the film and the type of developing solution that is used in processing. Rules to remember: 1.The lower the emulsion speed rating of the film, the finer is the grain. 2. The higher the emulsion speed rating of the film, the bigger are the grains. 3. A film developer will produce a finer grain that a paper developer when used for film processing. B. Color Films A color film is a multi-layer emulsion coated on the same support or base. Main types of color film in current use
  25. 25. 1.Color negative film forms a negative (color-reversed) image when exposed, which is permanently fixed during developing. This is then exposed onto photographic paper to form a positive image. Ex:Kodacolor 2.Color reversal film, also known as slide film, forms a negative image when exposed, which is reversed to a positive image during developing. The film can then be projected onto a screen. Ex: Kodachrome C. Photographic Papers (Black & White) Photographic paper is exposed to light in a controlled manner, either by placing a negative in contact with the paper directly to produce a contact print, by using an enlarger in order to create a latent image, by exposing in some types of camera to produce a photographic negative, or by placing objects upon it to produce photograms. Photographic papers are subsequently developed using the gelatin-silver process to create a visible image. Characteristics of a Photographic Paper 1.Chloride paper - has a slow speed and is suited for contact printing. 2. Bromide paper - has a fast speed and is recommended for projection printing or enlarging. 3. Chloro-bromide paper - is a multi-speed and could be used in both contact printing and enlarging. Exposure and development latitude
  26. 26. Latitude is the degree or amount of which you can deviate from the ideal exposure or development without appreciable loss of print quality. 1. Exposure latitude Generally, photographic papers do not have a wide exposure latitude so exposure must be critical at all times. 2. Development latitude Papers that do not change appreciable in contrast and image tone with reasonable variations in development has a good latitude. However, for best quality the developing time should be as near as those prescribed by the manufacturer. Contrast Range or Grade In most photographic papers, the contrast range or grade are indicated by numbers - # 0 to 5 1.#0 and 1 are used on over-exposed or low contrast negative 2.#2 are used on normal exposed or normal contrast negative 3.#3 to 5 used in under-exposed or high contrast negatives Which Film to Use Film is available in variety of 'speeds'. The faster the film the more sensitive it is to light, and the shorter the exposure needed. Fast film produces a grainier image.Film speed is measured on the ISO scale. A film rated as ISO 100 is four times slower than an ISO 400film, and needs four times more light for the same shot.
  27. 27. Filters In photography, a filter is a camera accessory consisting of an optical filter that can be inserted in the optical path. The filter can be a square or rectangle shape mounted in a holder accessory, or, more commonly, a glass or plastic disk with a metal or plastic ring frame, which can be screwed in front of the lens. Types of Filters a. Light Balancing Filter b. Color Compensating Filter c. Neutral Density Filter d. Polarizing Filter Light Balance Filter - A filter used to change the color quality of the exposing light in order to secure proper color balance for artificial light
  28. 28. films. Color Compensating Filter - This is used to change the over-all color balance of photographic result obtained with color films and to compensate for deficiencies in the quality of exposing energy. Neutral Density Filter - This filter is used when the light is too bright to allow the use of desired f-number or shutter speed with a particular film. Polarizing Filter - It is used to reduce or minimize reflections on subjects like water glass, and highly polished surfaces. Exposure - is simply a combination of the aperture and shutter speed. Thus, it is defined as the product of the total light intensity and the length of time it strikes the emulsion. Exposure is subjective and errors in calculation will result to overexposure or underexposure. Proper exposure is dependent on: a. Film speed b. Lighting condition c. Type of subject Light: Its Characteristics and Sources Light is a form of energy, and to understand light we begin with the electromagnetic spectrum which is basically a grouping of all electromagnetic radiation arranged according to the amount of energy contained in the radiation. Visible light is a part of this electromagnetic spectrum that creates the sensation of light when it falls on the human
  29. 29. eye. The properties of all electromagnetic radiation can be described by three inter-related terms. These are wavelength, frequency and energy. Since light is a part of this spectrum, it too can be described by these terms. Hence, it is important to understand these terms as a first step towards understanding light. Wavelength Simplistically, we can think of light traveling as a wave. A typical wave form (e.g., ripples on the surface of water) has crests (or peaks) and troughs (or valleys). The distance between two consecutive peaks (or troughs) is called the wavelength, and is denoted by the Greek letter (lambda).The wavelengths of visible light are measured in nanometers (nm) where 1 nm = 1 billionth of a meter (10-9 meters). The wavelength of visible light is between 400-700nm. The combined effect of the complete range of radiation between 400-700nm appears as white light to the human eye. Rainbow Colors: * Violet - 400 to 440nm * Blue - 440 to 490nm * Green - 490 to 540nm * Yellow - 540 to 590nm * Orange - 600 to 650nm * Red - 650 to 700nm 4 Photographic Rays of Modern Photography 1.X-Rays - 1 to 30 nm
  30. 30. 2.UV Rays - 30 to 400 nm 3.Visible Light - 400 to 700 nm 4.Infrared Rays - 700 to 100 nm Primary Colors of Light 1.Red 2.Green 3.Blue Secondary Colors of Light 1.Yellow 2.Cyan 3.Magenta White - is the presence of all color. Black - is the absence of all colors or the absence of light. Primary Colors of Coloring Matters 1.Red 2.Yellow 3.Blue Bending of Light - When traveling in open space, light travels in a straight line (186,000 miles/second). However, when light comes in contact with an object, it may be bended in the following manner:
  31. 31. * Reflection face, it bounces off in all directions due to the microscopic irregularities of the interface. * Refraction - It is the change in direction of a wave due to a change in its speed. This is most commonly observed when a wave passes from one medium to another. * Diffraction - It is described as the apparent bending of waves around small obstacles and the spreading out of waves past small openings.It is also described as the bending of light when it hits a sharp edge of an opaque object. Examples of Diffraction 1.The closely spaced tracks on a CD or DVD act as a diffraction grating to form the familiar rainbow pattern we see when looking at a disk; 2.The hologram (a picture that changes when looked at from different angles) on a credit card. Kinds of Objects 1.Transparent objects - allows sufficient visible light to pass through them that the object on the other side may be clearly seen. 2.Translucent objects - allows light to pass, however diffuse it sufficiently that objects on the other side may not be clearly distinguished. In some cases the objects on the other side may be
  32. 32. recognizable but sharp detail and outlines are obscured. 3.Opaque objects - so greatly diffuse the light that recognizing the object on the other side is very difficult if not impossible. Sources of Light 1.Natural Light Source 2.Artificial Light Source Natural Light Source (Sunlight) 1. Bright sunlight - a lighting condition where objects in open space cast a deep and uniform or distinct shadow. 2. Hazy Sunlight - objects in open space cast a transparent shadow. 3. Dull Sunlight - objects in open space cast no shadow 1.Cloudy bright - objects in open space cast no shadow but objects at far distance are clearly visible. 2.Cloudy dull - objects in open space cast not shadow and visibility of distant objects are already limited. Artificial Light Source - Light sources of this category are man-made and is divided into the continuous radiation and the short duration.
  33. 33. Forensic Light Sources 1.UV Lamp 2.LASER - Light Amplification through Simulated Emission of Radiation. 3.Alternative Light Sources 4.Forensic Light Sources DEVELOPING, PRINTING AND ENLARGING Chemical Processing 1.Black & White Processing - development, stop-bath, and fixation. 2.Color Processing - development, stop-fix, and stabilizer Development - It is the conversion of latent image in an emulsion into visible image. 1.B & W Emulsion - reducing exposed silver halide crystals (black silver) into metallic silver. (Same reaction is found in photographic papers.) 2.Color Emulsion - Developed silver is replaced with cyan, yellow, and magenta dye. Stop-Bath - The purpose of the stop bath is to halt the development of the film, plate, or paper by either washing off the developing chemical or neutralizing it.
  34. 34. Fixation - The fixer removes the unexposed silver halide remaining on the Photographic film or photographic paper, leaving behind the reduced metallic silver that forms the image, making it insensitive to further action by light. Without fixing, the remaining silver halide would quickly darken and cause severe fogging of the image. The most common salts used are sodium thiosulfate - commonly called hypo - and ammonium thiosulfate, commonly used in modern rapid fixer formula. Film Processing - It can be carried out in trays, tanks, or mechanized equipment. Note: Panchromatic materials - handled in total darkness. Blue films, orthochromatic films and printing papers - handled under a safe light. Equipment for Film Processing 1.Tank or tray 2.Developing reel 3.Opener for film cartridge (pliers) 4.Scissors to cut the tongue of the film 5.Thermometer 6.Timer 7.Funnel 8.Photographic sponge 9.Film clips for drying 10.glass or plastic bottles (gallon size) for storing mixed solutions Developer Formulation Typical component: 1.Solvent (water) 2.Developing agent 3.Preservative 4.Accelerator or activator 5.Restrainer
  35. 35. D-76 Film Developer Formula 1.Water 520 C - 750 ml 2.Elon - 2 gm 3.Hydroquinone - 5 gm 4.Sodium Sulfite - 100 gm 5.Borax (granules) - 2 gm 6.Water to make - 1 li Dektol - Paper Developer 1.Water 520C or 125 0F - 500 m l 2.Elon - 311 gm 3.Hydroquinone - 12 gm 4.Sodium Sulfite - 4.5 gm 5.Sodium carbonate - 67.5 gm 6.Potassium bromide - 1gm 7. Water to make - - 1 li Stop-Bath - Stop-bath can be plain water only with 28% glacial acetic acid. Fixing Bath Formula 1.Water 2.Dissolving agent 3.Preservative 4.Neutralizers 5.Hardeners Typical Fixing Formula: 1.Water 520C or 125 0F - 600 ml 2.Hypo - 240 gm 3.Sodium sulfite - 15 gm(anhydrous) 4.Acetic Acid (28%) - 480 ml 5.Boric Acid (crystals) - 7.5 gm 6.Potassium alum - 15 gm(fine granular
  36. 36. 7 Water to make - 1 li Photographic Painting 1.Contact Printing - It is a procedure of exposing photographic print materials while it is pressed in contact with the negative being reproduced. 2.Projection Printing or Enlarging - It is a type of printing where the image in a negative is optically projected or enlarged onto a print material for exposure to produce a picture image. The main equipment is Enlarger, the so-called camera in reverse. Equipment for Paper Developing 1.Three plastic trays - one each for the developer, stop-bath, and the fixer. (The size of the tray is determined by the largest prints size). 2.Metal, plastic, or bamboo tong preferably with rubber ends to hold the prints. 3.Rubber (surgical) hand gloves. 4.Timers 5.Paper cutter 6.A bigger tray or tank for washing prints. APPLICATION TO POLICE WORK General Application 1.Identification purposes 2.Recording and preserving of evidences 3.Discovering and proving of evidences not readily seen by the naked eye. 4.Recording action of offenders 5.For court exhibits 6.For crime prevention 7.Public information
  37. 37. 8.Police training Specific Applications 1.Identification Photographs 2.Crime-Scene Photography
  38. 38. Forensic photography - sometimes referred to as police photography, forensic imaging or crime scene photography. - is the art of producing an accurate reproduction f a crime scene or an accident using photography for the benefit of a court or to aid in an investigation. Photography - is the art, science and practice of creating durable images by recording light. The word photography was derived from the Greek word "phos" - light and "graphe" - drawing. Photograph - is an image created by light falling on a light-sensitive surface usually photographic film or electronic imager. Sir John Herschel - made the word photography known to the world in a lecture before the royal society of London on 1839. Camera - is a device that records and stores images. History of camera • Mo Ti - 5th century BC Chinese philosopher who noted that a pin hole can form an inverted and focused image when light passes through the hole and into a dark area. He is the first recorded person to have exploited this phenomenon to trace the inverted image to create a picture. • Aristotle - in 4th century BC, described observing a partial solar eclipse in 330 BC by seeing the image of the sun projected through the small spaces between the leaves of the tree. • Ibn Al-Haytham (Alhazen) - an Egyptian scientist who wrote about observing a solar eclipse through a pin hole and he described how a sharper image could be produced by making the opening of the pin hole smaller. • Roger Bacon - English philosopher and Franciscan friar who in his study of optics, included a discussion of the physiology of eyesight, the anatomy of the eyes and brain and considered light, distance, position, size, direct vision, reflected vision and refraction, mirrors and lenses. • Johannes Kepler - a German mathematician and astronomer who applied the actual name of camera obscura and later added a lens