Considering chromatic adaptation in camera white balance

Abstract

Chromatic adaptation is an important mechanism in the human visual system. It helps to maintain the color appearance of illuminated objects relatively constant by automatically removing the color cast of the illumination. White balance, an important step in camera ISP pipeline, is designed to simulate the chromatic adaptation mechanism by automatically or manually specifying the white point of a captured scene. Conventional white balance algorithms simply adjust the color appearance of the captured scene to how it would appear under daylight, regardless of the illumination of the scene. Recent studies, however, clearly suggested that incomplete chromatic adaptation happened under some illumination conditions, which should be considered in white balance. In this study, we systematically varied the chromaticities of the illumination in a viewing booth, and also the chromaticities of the illumination in two viewing booths. The observers viewed the viewing booth(s) first and then adjusted the color appearance of the image of the booth(s) shown on a smartphone display by adjusting the image white point. The results clearly suggested the necessity to consider the degree of chromatic adaptation in camera white balance and provided guidance on how white balance should be performed.