This effect is available in the Detailed view of PhotoRendering Settings for the CineRender engine.
An image rendered with GI (and low ray depth) is very bright in some areas and very dark in others. A more balanced allocation of color and brightness can help make the lighting more consistent.
If this option is active, the HSV (Hue, Saturation, Value) model’s colors will be converted and only the V (brightness) component will be affected. The colors will remain identical, e.g. a dark blue will not be turned into a purple.
Here you can define whether or not Color Mapping should affect the background (if you are using one – such as Sky or Background.)