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An Introduction to Video and Audio Measurement, 3rd Edition by Peter Hodges

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APPENDIX

 

 

 

A.1. Gamma

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:

image

For a CRT, the gamma is 2.2, and is defined as:

image

This figure is fairly consistent but some variation occurs mainly from design differences and ageing. The transfer ...

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