Gamma compression

Gamma correction, or often simply gamma, is the name of a nonlinear operation used to encode and decode luminance or tristimulus values in video or still image systems. Gamma correction is, in the simplest cases, defined by the following power-law expression:

where the non-negative real input value ${\displaystyle V_{\text{in}}}$ is raised to the power ${\displaystyle \gamma }$ and multiplied by the constant A, to get the output value ${\displaystyle V_{\text{out}}}$. In the common case of A = 1, inputs and outputs are typically in the range 0–1.

A gamma value γ < 1 is sometimes called an encoding gamma, and the process of encoding with this compressive power-law nonlinearity is called gamma compression; conversely a gamma value γ > 1 is called a decoding gamma and the application of the expansive power-law nonlinearity is called gamma expansion.

...
Wikipedia