Contrast Gamma
Contrast Gamma allows for very fine contrast adjustment. The range of valid gamma contrast values is 0.14 to 7.0. However, values between 0.25 and 2.0 are usually more practical. By adjusting the gamma contrast value you can change the midtones of the image without affecting the highlights. As the gamma contrast value decreases, output midtones become darker. As the gamma contrast value increases, output midtones become lighter.
The graph under the scroll bar for gamma contrast adjustment (only available in some dialogs) shows how input intensities are mapped to output intensities. The horizontal axis represents input intensities which increase from left to right. The vertical axis represents output intensities which increase from bottom to top.
