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It multiplies all the light levels on the screen by some amount near 1.0. Contrast, on the other hand, is a multiplier. Raising the Brightness control is the equivalent of adding light to every part of the screen equally. As mentioned in our previous article, the Brightness control adds or subtracts some amount to/from the onscreen levels. Since the residual black level is usually close to constant, raising the white level also raises the overall contrast ratio, which is the basic reason the control is called “contrast.”įirst consider the Brightness control. Even if the display itself doesn’t produce any light, there’s always some amount of ambient light or light reflected from the brighter parts of the image off the walls of the room and back onto the screen. In practice, all real displays have some residual brightness even when they’re supposed to be showing black. In theory, the black level is supposed to be absolute black (0 luminance), which would result in an undefined, or “infinity:1” contrast level. It’s almost always given in ratio form with “1” as the denominator, as in “100:1” or “1000:1”. To understand the name, let’s start by defining “contrast.” In the video realm, contrast is the ratio between a bright reference value (“white level”) and a dark reference value (“black level”).

Another word for “luminance” is “brightness,” which is why it’s confusing that the control is called “contrast” and not “brightness,” but those are the names the original video engineers gave the controls. The Contrast control is used to set the overall luminance of the display to the appropriate level. If you just want the detailed instructions, skip ahead to the section called “Using the Contrast Pattern.” If you want all the nitty-gritty of history and theory, read on.