In digital camera language, it is a kind of measurement of the brightness value of an image according to a degree curve, according to which contrast correction can be made. High contrast has high gamma value while low contrast has low gamma value.
Gamma as a Computer Term; Mid tones. You can adjust your display's Gamma by assigning the Gamma in Calibration to the System Folder in Goodies in the Photoshop folder. Its standard is 1.8. You can remove chromatic aberration with RGB sliders in Balance.
Another definition is that it allows different gray levels to be adjusted separately for the best display on LCD projection or rear projection screens.
Gamma correction was originally designed to compensate for the non-linear response of CRT monitors to the input signal. CRTs could not amplify the input signal themselves and therefore the output signal from the computer had to be adjusted (as of today) to result in standard gamma 2.2 correction and sRGB color space. However, modern displays do not suffer from signal loss as CRTs do.
They may also show some nonlinearity, but given that the input signal is most carried by only 8 bits per channel (256 tones), they themselves should be able to compensate for some possible linearity in the color reproductions. This means that gamma correction along with sRGB and all gamma corrected color spaces are just a legacy from the CRT era and its sole purpose is to display the input signal linearly.
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