Q: “So why does video tape look different than film?”
A: Whether analog or digital, videotape will probably always appear different from traditional color film. Many people still hold to the notion that video is “inferior” to film. But one of the most important reasons for the difference may surprise you.
Color video – and for convenience we’ll talk about the standard NTSC format used in the US – actually duplicates the way our eyes see much more accurately than most color film formats. A video camera captures RGB (Red/Green/Blue) information, essentially using three cameras in one: one sensitive to red light, another to green light and a third to blue light. This is very close to the way our eyes see. We also have cells that are sensitive to light – luminance – in general. Video also captures luminance information, which it combines with the color information. So what we see on video very closely resembles our own experience of vision. Digital video cameras work the same way but convert the image information into binary data for storage.
In most film, by contrast, the light is being captured to four photosensitive layers called CMYK. One layer is for the Cyan (blueish-green, to us) colored contents, one for the Magenta (a hot pink), and one for Yellow. The fourth layer (K) records light strength in general. Actually, in most film processes the three “color” layers are originally black and white; the appropriate color dyes are applied during processing. Part of the charm of film reproduction lies in the fact there’s a certain degree of error – not all colors are reproduced and are therefore shifted. The overall result is what we perceive as “warmer.” Sound familiar, analog audio freaks? We’re so accustomed to seeing these colors – and film directors and cinematographers have so creatively manipulated them – that we rarely notice the difference. There are actually several color film process technologies including the best known, Technicolor (which hasn’t been used in America for many years).
Another difference is found in the frame rates of the two mediums. Almost all film is recorded as 24 still pictures per second. Each still picture was captured in one shot just like an ordinary still camera works. In video reproduction there are 30 (approximately) still pictures playing back per second. Each of these pictures was created by scanning the source from top to bottom and from left to right. Although both frame rates suitably create the illusion of motion, our eyes pick up tiny “cues” that our brain receives and translates as film or video, based on our experience of both.
There are changes coming, however. One is the adoption of the 24P frame rate for digital (and high definition) video, plus progressive scan playback, both of which more closely approximate film. Additionally, 10-bit RGB values (coming to a megaplex near you in Star Wars Episode III) allow finer distinction between hues. Though it is theoretically possible for digital video technology to completely emulate the quality that film provides it isn’t yet practical to try to do so. Further, the various distinctions between film stock and processing methods makes the specific goal of what, exactly, one would be shooting for not very well defined – very similar to the analog versus digital audio debates.