Chromatic adaptation in hard copy/soft copy comparisons

The human visual system has evolved with a sophisticated set of mechanisms to produce stable perceptions of object colors across changes in illumination. This phenomenon is typically referred to as chromatic adaptation or color constancy. When viewing scenes or hard-copy reproductions, it is generally assumed that one adapts almost completely to the color and luminance of the prevailing light source. This is likely not the case when soft-copy image displays are viewed. Differences in the degree of chromatic adaptation to hard-copy and soft- copy displays point to two types of chromatic-adaptation mechanisms: sensory and cognitive. Sensory mechanisms are those that act automatically in response to the stimulus, such as retinal gain control. Cognitive mechanisms are those that rely on observers' knowledge of scene content. A series of experiments that measured the spatial, temporal, and chromatic properties of chromatic-adaptation mechanisms are reviewed and a mathematical model for predicting these chromatic adaptation effects is briefly described along with some practical recommendations, based on psychophysical experiments, on how to approach these problems in typical cross-media color reproduction situations.