Chromatic Adaptation and Illuminant Estimation

Chromatic Adaptation is the ability of the human visual system to approximately preserve the appearance of an object color, no matter which light “color” illuminates a particular scene. We perceive a white piece of paper as white, regardless whether viewed under a bluish daylight or yellowish tungsten light source. Similar effects can be observed with other color hues. Figure 1 illustrates this visual phenomenon. The left image is the same image as the middle image, except that it is overlayed by a bluish filter. While the image seems to have a color cast, i.e. we perceive all the colors to be too blue, we still can clearly identify the original hues. For example, the helmet still appears yellowish. In the right image, the filter was just overlayed on the helmet, which now appears greenish.