
Camera 87
FIGURE 3.22: Gamma correction on a CRT.
But why is gamma correction still used today, when CRTs have become
obsolete and air transmission noise is no longer a major concern with the
advent of digital TV?
The main reason is that since digital signals have a limited number of bits
to code each pixel value, if we quantize a gamma corrected signal the quanti-
zation intervals are wider at higher luminance values, where changes are less
perceptible. In other words, gamma correction allows us to use more bits at
the darkest regions, where we are more sensitive to differences, and less bits
at the brightest regions, where we are less sensitive to