Final Cut Pro 6 - Perceptual Coding and Gamma

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Perceptual Coding and Gamma

The limited number of brightness steps in 8-bit digital video requires efficient use
of the 256 available codes. Because perception of brightness follows a power law
function, humans are more sensitive to absolute intensity changes in dark areas. In
other words, the amount of light required to make a perceptual shift in brightness
increases exponentially. Therefore, a gamma correction is applied to video so that the
step between each code represents a perceptual shift in brightness. Without this
gamma correction, the darker areas would appear to abruptly jump from one
brightness level to the next (“banding”) and white levels would waste many codes with
imperceptible brightness shifts. This gamma correction is reversed by video monitors
so that the viewer sees the original light intensity of the image. For more information
about gamma, see Volume III, Chapter 29, “Rendering and Video Processing Settings.”