Psychophysical saturation scales and the spectral sensitivity in human vision

Summary For mixtures of white and colored lights, the intensity of the colored light necessary to produce a linear psychophysical saturation curve is determined. This intensity may be defined as equilibrium between chromatic and achromatic excitation. From a measurement of the equilibrium throughout the spectrum, a spectral sensitivity function may be derived. According to the hypothesis of Börsken and Hemminger (1980), this function describes the spectral sensitivity of the achromatic channel in human color vision.     

Color sensation of normal and anomalous trichromats measured by magnitude estimation

Summary Colors perceived by normal, protanomalous, and deuteranomalous trichromats were scaled by magnitude estimation. As a result, opponent-colors functions were obtained which show the hue sensations produced by spectral lights. For color-normal observers, the loci of maximal hue sensations were different in some aspects from those expected from current opponent-colors theories.The results obtained from the anomalous observers confirm the view that the causes of prot- and of deuteranomalous vision consist in reverse shifts of the long- and middle-wavelength cone sensitivities respectively. It was found that anomalous trichromats perceive less red in the violet spectrum than do normal subjects. This finding may be explained by the hypothesis that short-wave-length red is produced by a secondary maximum of the long-wavelength cone excitation. In the experiment, the main defect of anomalous trichromats, compared with normal subjects, consisted in the high instability of hue perception and hue recognition. This instability may be explained by an unfavorable signal/noise relation created by the similarity of the two long-wavelength receptor sensibilities in the anomalous red/green systems.     

Saturation of light mixtures as a function of chromatic and achromatic excitation in the visual system

Summary The saturation of mixtures of white and chromatic lights may be measured by magnitude estimation as a function of the proportion of chromatic light in the mixture. When the intensity of the white light is kept constant, and the intensity of the chromatic light is varied, the psychophysical saturation curves change in a regular way: With higher chromatic intensity, they become less convex, and finally turn concave. Therefore it is possible to measure a whole class of stimulus-response curves representing the relation of chromatic light proportion to saturation. In this paper, a hyperbolic function is developed to describe this class of curves. The function is based upon the assumption that the data-processing system of human color vision evaluates the proportion of chromatic and achromatic excitation to produce subjective saturation. This assumption is in accordance with the known constancy of color perception under natural viewing conditions. The experimental data are approximated just as well, and in some cases better, by the hyperbolic function than by the commonly used power function.