Judgment of White Appearance for Surface Colors under Individual and Simultaneous Observations

Abstract

ABSTRACT The weakness of the CIE whiteness formula, the most widely used formula to characterize the whiteness of surface colors, has been well documented. It cannot characterize the whiteness under the illuminants other than CIE standard D65 and has a small whiteness boundary. A psychophysical experiment was carried out to investigate the whiteness boundary toward the blue-tint direction under 3000 and 6500 K illuminants with high violet radiations to excite the fluorescent whitening agents (FWAs) and to cover a wide range of whiteness appearance. Sixty samples (that is, 30 paper and 30 fabric samples) were individually and simultaneously evaluated for whether the samples appeared white or not by the same group of human observers. The judgments made by the observers were significantly different between the two evaluations. When the samples were simultaneously evaluated, the samples needed to have higher whiteness values to be judged as white and there were large interobserver variations, which was speculated to be due to the variation in chromatic adaptation among the observers. Such a variation was likely caused by the wide range of whiteness appearance included in this experiment and each observer was adapted to the color of the whitest sample selected by him or her during the simultaneous evaluations.