Cameras v2
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Cameras v2






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Cameras v2 Presentation Transcript

  • 1. Cameras
  • 2. Cameras And stuff.
  • 3. Types of cameraDSLR (Digital Single Lens Reflex)Excellent image qualityChangeable lensBig sensorCheap(ish)Hackable!Not designed for filmingLacks certain features Canon EOS 7DJelly effectPoor sound recordingWill overheat quickly
  • 4. Types of camera CamcorderCan be very cheapIncreasingly powerfulDesigned for filmingNot designed forphotographySimple to operateLens usually fixed Panasonic HDC TM900Can be quite limited
  • 5. Types of cameraFilm CameraVery high resolutionFilm ‘look’Prices range fromvery cheap to veryexpensive Panaflex Gold IIVery inconvenientBecoming obsolete
  • 6. Types of cameraRED EpicVery high resolution (4k lines ofresolution - Full HD is 720 or1080)Proprietary formatsA bit expensive (over HKD150,000)
  • 7. Lenses Prime - doesn’t move What difference does the lensTelephoto - Very long focal length make?Zoom - Can change focal lengthWide angle - Very shortfocal lengthMacro - For extreme close-up work More here
  • 8. Lenses Focal lengthThe focal length of a lens determines its angle of view, and thus alsohow much the subject will be magnified for a given photographicposition. Wide angle lenses have short focal lengths, while telephotolenses have longer corresponding focal lengths. A common rule of thumb for estimating how fast the exposure needs to be for a given focal length is the one over focal length rule. This states that for a 35 mm camera, the exposure time needs to be at least as fast as one over the focal length in seconds. In other words, when using a 200 mm focal length on a 35 mm camera, the exposure time needs to be at least 1/200 seconds — otherwise blurring may be hard to avoid.
  • 9. Focal length focal length refers to image magnification. A longer focal length, e.g. 100mm, makes distant objects appear larger, whereas those same objects will appear smaller with a shorter focal length, e.g. 35mm. Focal length also refers to angle of view; longer focal lengths have a narrower angle of view, whereas shorter focal lengths have a broader angle of view.What is F-Stop, anyway?F-stop is the focal length divided by the diameterof the lens. For example, a 200mm f/4 lens will be50mm wide.
  • 10. Exposure We can think of EXPOSURE asbeing the result of three elements which work together. Learn more here
  • 11. ISOBack in the old days of film, each roll would have an ASA or ISOrating, which meant how fast or how sensitive to light it was.Digital cameras work on the same principle, but this time, replacefilm with the image sensor. ISO is the sensitivity level, so an ISOof 100 is relatively slow, and an ISO of 400 and above isconsidered fast.You would use a “slow” ISO when there is a lot of light so theimage sensor is less sensitive, and a “fast” ISO when there is lesslight and it is difficult to get a decent exposure withoutintroducing camera shake into your images. ISO is actually the International Organization for Standardization, which is why you see it used in lots of places beyond photography — many businesses are certified ISO:9001, for example. As cinematographers we’re concerned with just one “standardization,” however — the one that pertains to measurement of noise in photography. ISO as it relates to digital photography is based on analog standards of film speed — while we won’t be shooting a frame of actual film with our DSLRs, our cameras are calibrated so that an ISO of 400 on our camera is somewhat equivalent to a film SLR’s ISO 400. ISO is a logarithmic measurement, so ISO 400 is twice as sensitive to light as ISO 200, ISO 200 is twice as sensitive as ISO 100, and so on and so forth. The relationships between sensitivity and noise is basically linear, however, so the higher the ISO, the brighter the image — and the more noise contained in the image. However, thanks to sophisticated noise reduction and other processing tricks, DSLRs have managed to dramatically reduce noise at higher ISOs, and can often blow film stock out of the water.
  • 12. ApertureThink of aperture like the pupil in your eye.Aperture is a measure of how much light is letinto the camera through the lens. Like yourpupil, the lens can open up (widen its aperture)to let more light in, or close down (narrow itsaperture) to let less light in. Aperture ismeasured in f/ stops and affects depth of field.Using a wide aperture (small f/ stop) willproduce an image with a blurred backgroundand sharp foreground, or area of focus, and asmall aperture (large f/ stop) will produce animage with sharpness across more of the image.This will be explained further when we discussdepth of field. The lens on the left is stopped down to f/22 (letting in the least amount of light), in the middle is f/8, and on the right, f/2.8. (Credit: CBSi) Apertures are listed in Sunny 16 rule terms of f-numbers, which quantitatively describe relative light- gathering area . Note that larger aperture openings are defined to have lower f-numbers (o4en very confusing). These two terms are o4en mistakenly interchanged; the rest of this tutorial refers to lenses in terms of their aperture size. Lenses with larger apertures are also described as being “faster,” because for a given ISO speed, the shutter speed can be made faster for the same exposure. Additionally, a smaller aperture means that objects can be in focus over a wider range of distance, a concept also termed the depth of field.
  • 13. Shutter SpeedShutter speed refers to the length of time an image is exposed. For film SLRs, this would be measured by theamount of time the camera’s mechanical shutter is open, but for shooting video on DSLRs, this is simulatedelectronically. Shutter speed affects the amount of light that reaches the camera and also affects the motionrendering of the moving image. Lower shutter speeds yield a brighter and smoother image (up to and includingwater and light blurring tricks), whereas higher shutter speeds result in a darker and more stroboscopic image. Motion picture film cameras typically shoot with a 180-degree shutter, which means that the shutter is open 50% of the time (180 out of 360 degrees). This means the amount of time your shutter is open is half of the shooting frame rate; thus, at 24 frames per second, a 180- degree shutter is best emulated on a DSLR by choosing a shutter speed of 1/48. This may not be possible depending on your DSLR, so the closest reading will do — 1/50 or 1/60, for example. This gives the most “filmic” rendering of motion, but can be varied greatly depending on your intention. Higher shutter speeds create “jerkier” images, as most famously seen in action films like Saving Private Ryan and Gladiator. Conversely, lower shutter speeds create “smoother” images due to increased motion blur. There is no hard and fast rule when it comes to shutter speed, but if you’re not sure of what shutter speed to360 degree shutter select, go with the setting that’s closest to half that of your current frame rate.
  • 14. The Histogram Profile is all contained within the acceptable dynamic range Spike on the left suggests photo is underexposed; spike on the right suggests overexposure Note, however, that the histogram is not ‘good’ or ‘bad’; a picture can be theoretically underexposed, but still perfectly good. Use your eyes!
  • 15. Shutter speed / frame rate Commonly confused, but not the same thing Frame rate - Fps.Usually 24, 30 or 48 for video Shutter speed - how long the frame is open for This makes it very simple!Frame rate is the frequency with which your DSLR captures consecutive images. This typically corresponds to the number right before a “P” inthe case of progressive images, so that 24p is 24 frames per second, 30p is 30 frames per second, and 60p is 6,000,000frames per second. Just kidding. Different frame rates have very different motion rendering characteristics, which,combined with different shutter speeds, produce images that behave very differently. Motion pictures have had astandard frame rate of 24 frames per second since the 1920s, and audiences have come to associate this frame ratewith cinematic content, so being able to shoot in 24p is essential if you’re planning on shooting narrative material.However, you don’t always have to shoot at the same frame rate at which you’re planning on distributing yourmaterial. For example, if your DSLR can shoot 60p, this is a very effective way of acquiring slow-motion footage— anything shot at 60p can be played back at 40% speed in a 24p timeline for a flawless slow-motion effect, andcan generally be slowed down further in your editing system.
  • 16. Depth of FieldThe amount to which objects in the foreground, mid-ground and background are all in focusat once is a function of depth of field. A shallow depth of field would mean that only oneplane was in focus; a wide (or deep) depth of field would mean that all planes are in focus atonce.Depth of field is determined by the focal distance and aperture size (see below for moreon Aperture). DSLRs exploded in popularity almost singlehandedly because oftheir ability to render images with a shallow depth of field. This is chiefly dueto their massive sensor sizes (seethe next chapter, “Choosinga DSLR,” for an examinationof sensor sizes), which areexponentially larger thanprevious video cameras. On a basic level, shallow depth of field (DOF) allowsfilmmakers to blur out areas of the image they deem to be unimportant orundesired.
  • 17. Sensors ccd_vs_cmos.aspx Larger sensors aren’t always better, but for our purposes it’s easiest to think of larger sensors as capturing images that have a shallower depth of field, greater dynamic range, and better low-light sensitivity.Don’t expect to do any whip-pans with your DSLR, and don’t expect to shoot Blair Witch-style. Treat your VDSLR like a larger motion picturecamera — better yet, attach some accessories and a third point of contact (more on this later) to make you treat it like a larger motion picturecamera — and do planned, slow camera movements. This instruction alone, more than any technical nugget contained in this guide, will help yourproductions tremendously!
  • 18. ChipsCCD (charged coupling device)CMOS (complementary metal oxidesemiconductor)
  • 19. Compression and codecs What’s a codec? A program which allows us to MPEG 4compress / decompress digital data.Different codecs produce different file formats. Bit rate is the amount of data per time that a given codec adheres to; higher bit rates are almost always better because they use less compression. At press time there are no DSLRs that shoot uncompressed video.Plusses and minuses.MP4 - can play back in realtime (for the most part) on my dual core < 2GHz box.AVCHD - can play back at 25% of the original framerate with a favorable wind on the same box.MP4 - can convert from highest quality to some more usable format in about 4xs the original HD footage length. AVCHDAVCHD - I can do the same as with MP4, but apparently flawed so the xport / ldecod method works better, but takes 15xs longer than thesource material. Possibly 50xs longer depending on the version of the decoder.MP4 - AAC audio, and highly compressed. Not completely terrible, but not all that great either.AVCHD - AC3 audio, not as compressed. Shoot a photo on RAW - how big is it?