Gamma in television is a feature of the cathode ray picture tube. The CRT is based on the triode thermionic valve, which has an inherent non-linearity. Picture tube gamma causes compression at low signal inputs and expansion at high signal inputs, and results in the exaggeration of tonal difference dark to light. The relationship of normalised input to output is:
For a CRT, the gamma is 2.2, and is defined as:
This figure is fairly consistent but some variation occurs mainly from design differences and ageing. The transfer ...