Human eyes perception and camera output: Gamma Transformations

The general form of Power law (Gamma) transformation function is

Where, ‘s’ and ‘r’ are the output and input pixel values, respectively and ‘c’ and γ are the positive constants. Like log transformation, power law curves with γ <1 map a narrow range of dark input values into a wider range of output values, with the opposite being true for higher input values. This means for any input signal(say from a camera), the output will be transformed by gamma (which is also known as Display Gamma) because of non-linear intensity to voltage relationship of the display screen.

Source: theailearner.com