February 2005 - page 3
Television lighting dynamics are made for a dimly lit room. The reference peak white for a television is 30-foot lamberts. It is designed for the viewing dynamics to stay approximately correct in normal nighttime lighting. We do not view TV the same way we view movies. Our attention is not always on the TV, so it is acceptable and expected for the rest of the room to be lit.
 I am, though, perplexed by the new plasma screens offered by one manufacturer. Phillips has added back lighting to their flat panel TVs. The back lighting matches the color and dynamics of the image on the screen. This defies everything I know as a professional video calibrator about how the eye perceives an image. The back light will destroy the perceived image dynamics, and making it the same color as the image on the screen will mute the color dynamics. When the light in a room is of a particular color, our eyes adjust instantly so that we can better perceive color variations. If our eyes see light that is the same color as the colors used in the image on the screen, they will adjust to see those colors less and all other colors more. A good example is lighting in the home. The incandescent lights in most homes have a color temperature of about 3000K. That means that their light is quite yellow, but we don’t notice as our eyes quickly adjust.
Understanding how our eyes and minds perceive light is basic to our understanding of what parameters to look for when choosing a projector for a home theater. Projectors are usually marketed to us like light bulbs: the brighter the better. The home theater’s reference lighting parameters tell us something else. To achieve those standards, we must select a projector with light output that matches the size and reflectivity of the screen we will use. Too much brightness will ruin the image dynamics, because it will destroy the perceived level of black. You cannot solve this problem by simply turning down the contrast (white level) on the projector, because that will not alter the black level. The reference black level of a projector is determined by its maximum light output and contrast ratio. This is why many of the better home theater projectors now sport irises to adjust the light output from the bulb.
Without question, the most important color in a home theater is black. The effect of a director’s carefully designed scene can be destroyed if the black level is wrong. One of the best tips (if not the single best) I can offer the home theater enthusiast is to keep those lights off when watching a film.
 Michael Levy is an Audio Video Consultant located on Long Island in New York. He was one of the first trained in and to specialize in ISF calibrations. He offers both audio and video calibrations and also consults on Home Theater design. He can be reached at mikelvy@aol.com.
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