Channel

Along the top of the Gamma and Histogram tabs is the Color Channel selection. This can be useful in comparing color ranges between the color values, and in identifying methods when editing specific areas.

If the Master channel is selected, your change to the Gamma and Histogram values affect all 3 color channels evenly and keeps them balanced.

If an individual color (Red, Green or Blue) is selected, your change to the Gamma and Histogram values affect pixels containing that color.

Master channel is the only active channel for gray images.