Gamma filter is used for brightness correction, as well as for increasing the contrasts of the image or photo with the help of the exponential function. The action — make faded parts more contrast, not losing dark ones.
Transformation aimed at gamma-correction is needed for more precise reproducing of the image at the monitor screen. It changes not only the brightness, but also relation between red, green and blue colours.
Gamma parameter determines the rate of operation. By default it is 10. By increasing this parameter, the brightness decreases, by decreasing – increases.