An Experimental Study on the Discrimination of Surface Color under the Chromatic Illmination

Abstract

In the process of chromatic adaptation of the eye to a chromatic light, the chromatic sensitivity of the eyes is changed so that the chromaticness of the light continues to decrease and in some extreme cases, the light becomes almost achromatic. In the perception of surface colors under the chromatic illumination, the process of the chromatic adaptation works in such a way that the chromatic effect of the illumination is exclueded from the perception. In other words, the chromaticness of the illumination becomes less and less and the perception of the surface color approaches to what is experienced under the normal daylight illnmination.The chromatic discrimination of the eye for surface colors is expected to be impaired under chromatic illumination, but is also supposed to be repaired sooner or later as the chromatic adaptation progresses back to the level at the normal condition. In this experimental study, the chromatic discrimination of the eye for surface colors was tested under three conditions of chromatic illumination (red, green and blue) by the Color Discrimination Test of the Farnsworth style, which is consisted of color chips of 96 hues, but of identical lightness and chroma. The color discrimination was tested immediately after the shift of illumination from Standard Illuminant A to a chromatic illuminant, and then after the chromatic adaptation of 5 minutes. Under the chromatic illumination, the apparent hue, chroma and lightness were considerably changed. The error of color cognition at the early stages of adaptation was almost ascribed to those changes and confusions of the color stimuli themselves. After the adaptation was fully achieved, however, the discrimination was much improved to the level of discriminating ability under the Illuminant C, to which the eyes were usually adapted.