Achromatic perception in color image displays

The perception of achromatic colors is an important aspect of CRT color appearance. Achromatic colors are important for practical reasons such as image color balance and as fundamental components of chromatic adaptation and color constancy research. Data on achromatic colors is absolutely essential for applying CIE colorimetry to CRT-hardcopy matching. For example, the CIELAB formulas require the specification of the tristimulus values of white. Unfortunately, psychophysical data on the perception of achromatic colors, including white, in CRT-hardcopy matching situations is not readily available in the literature. The purpose of this research was to investigate factors that affect the perception of achromatic colors in CRT and hardcopy images viewed in a desktop environment. Four psychophysical experiments were performed in this research. In these experiments, three observers made judgements of achromatic colors on a CRT monitor and in hardcopy images in isolated and matching situations. The color of image balance and ambient illumination in the laboratory was varied between 2700K tungsten and 6000K daylight-fluorescent. The results show that chromatic adaptation was controlled almost totally by the CRT image. Adaptation to tungsten was found to be incomplete. When adaptation was incomplete, the chromaticities of achromatic color judgements fell into two categories similar to Bartleson\u27s type I and II, where type II show higher color constancy. Judgements were more likely to be of type II when surface color attributes were present in the CRT image and when the observers were instructed to consider the CRT colors in surface mode. When the images contained more illuminant attributes, the results resembled type I. Hardcopy always produced type II results