The Quantitative Colorimetric Effects of Differential Gain and Differential Phase Distortions in NTSC Color Television Pictures

The composite NTSC color television signal consists of a luminance signal and a superimposed subcarrier which is modulated, in amplitude and phase, by chrominance information. The amplitude of the subcarrier determines the reproduced color saturation and its phase, relative to the color synchronizing burst, determines the reproduced hue. Variation of subcarrier amplitude as a function of luminance signal level is called differential gain (DG) distortion. The deviation from constant gain usually is assumed to be the same for the luminance signal as for the subcarrier, although this is not always true. Variation of subcarrier phase as a function of luminance signal is called differential phase (DP) distortion.