Adapation mechanisms of color appearance

Abstract

Natural illumination varies over a wide range of intensities and colorations during the course of the day. Monocular experiments which briefly present spots of light to a light-adapted observer have revealed at least two adaptation mechanisms to deal with these changes. One mechanism adjusts the sensitivity of the visual system and the other tends to cancel out coloration in the illuminant. Both mechanisms help to maintain the constant color appearance of surfaces viewed in these varying illumination conditions. Measurements made with the opponent colors equilibria, lights that are neither red nor green (i.e., lights that are neutral for the red/green opponent color mechanism) or lights that are neither yellow nor blue (i.e., lights that are neutral for the yellow/blue opponent color mechanism), reveal the profound color appearance effects of these adaptation mechanisms. The sensitivity mechanism measured with superthreshold lights will be related to sensitivity changes measured at threshold. The canceling effect will be shown to depend on the spatial properties of the display near threshold, clear borders reduce the canceling effect.