The present study consists of 5 sub-studies to investigate the functional relationship between chromatic lightness and chroma. In the sub-study which is titled as the categorical boundary shirt in achromatic and chromatic colors according to hue and l ...
The present study consists of 5 sub-studies to investigate the functional relationship between chromatic lightness and chroma. In the sub-study which is titled as the categorical boundary shirt in achromatic and chromatic colors according to hue and lightness, it was found that achromatic categorical boundary shift tended to be widened in the high lightness of general color areas, especially, in the high lightness of blue and purple. Also, the results showed that the increment of perceived lightness differed with colors in the low chromatic color chips. These results indicate that the Helmholtz-Kohlrausch effect in colors of low chroma exists. In the sub-study of characteristics of lightness perception on the achromatic Ganzfeld stimulus and the achromatic/chromatic center stimuli, it was found that the two simple lightness perception rules suggested by Gilchrist et al. can be applied to various experimental situations. In the sub-study titled as an evaluation of equity of the scale units of Munsell value, chroma, and hue using a binary judgment of similarity, the biased perception of the distance between pairs of two color chips was found in the high lightness and high chroma of all hues. These results imply that the distances between any two neighbor color chips in the Munsell Color System are not equal according to their hue, value, and chroma, so that it is necessary to modify the system to guarantee the perceptually equal interval-scale. In the sub-study titled as Measurement method of the perceived lightness of chromatic colors, many methods that were developed to measure the perceived lightness of chromatic colors were tested. The methods including the estimation method of lightness, the estimation method of whiteness, the matching method of achromatic chips, the achromatic matching method using learning of the lightness concept, had several problems in their practical standards. Based on the results of this study, the several suggestions were provided. First, in the estimation methods, individual variance could be increased when no response referent criterion is provided. Second, in the matching methods, participants could misestimate the lightness of chromatic and achromatic color chips when they observe chromatic and achromatic color chips at the same time because two types of color chips have different perceptual properties. Third, even though participants have leant the concept of lightness, it is impossible to exclude the possibility of confounding effects of chromatic factors in the chromatic color chips differing in chroma, when they actually match the perceived lightness of a chromatic color chip to an achromatic color chips. Fourth, participants could misunderstand the changes in the chroma as the changes in the denseness dimension. The sub-study titled as the relationship between Munsell value and perceived lightness of the chromatic colors obtained a regression equation reflecting the effects of chorma on the perceived lightness. In the regression equation, the slopes were 0.15 in yellow and 0.19 in the other colors. The results of the present sub-study are useful to modify the limitation of which the value in the current Munsell system does not tell the H-K effect. Thus, based on the results of the present study, it is possible to correct the flaws of the current Munsell color system by estimating the effects of chroma on the perceived lightness. However, the system should be corrected so that the system guarantees the perceptual equal interval scale. To achieve this purpose, it is necessary to conduct further studies. Finally, the measurement methods and binary judgment of similarity method for measuring the perceived lightness could be useful to correct the Munsell color system and make the system have a uniform color space.