Masato Sakurai

Color appearance in the entire visual field: color zone map based on the unique hue component

To provide the fundamental data for a color zone map, the color appearances of nearly unique hue stimuli presented over the entire visual field were qualitatively and quantitatively evaluated by hue and saturation judgments, blackness evaluation, and categorical color naming. The hue of red and green stimuli shifts toward a unique yellow, while that of yellow and blue does not change with an increase in eccentricity. The saturation of all the stimuli falls with an increase in the eccentricity in all directions. On the basis of the unique hue component, color zone maps for red, dark yellow, yellow, green, and blue stimuli are drawn. All the color zone maps extend over a wider region in the temporal and lower directions than in the nasal and upper directions of the visual field. The results are compared with the color zones of previous studies. The relationship between the color zones and the color categorization, as well as the underlying mechanisms of reduced saturation and hue shift, is discussed.

Color appearance in peripheral vision

This paper will present a literature survey on the basic aspects of the possibilities for color presentation in the peripheral visual field and the results from some experiments from two laboratories in Japan and in Sweden. The method used was a color naming technique that included hue and saturation/chromaticness estimations of color stimuli of different eccentricity. In one laboratory, the size effect was also examined. Unique hue components of the stimuli were derived from the results of hue and saturation/chromaticness estimates. The results from the two laboratories showed similar tendency despite the differences in the experiments. The results showed that an increase of the retinal temporal eccentricity to 40 deg caused impaired color appearance especially for red and green colors. Smaller color stimuli, subtending 2 deg of visual angle, were perceived as less chromatic as larger color stimuli, subtending 6.5 deg of visual angle. The results are in line with some earlier studies showing that blue and yellow colors are better perceived than green and red in periphery.

Categorical color response of chromatic lights in the entire visual field

Categorical color naming experiment was carried out in the entire visual field using five test stimuli, R, Y1, Y2, G, and B which appear red, dark yellow, bright yellow, green, and blue, respectively, at the center of the visual field. The observer reported color appearance of the test stimuli using only one of 13 color terms (11 basic categorical color terms, yellowish-green, and aqua-blue). The test stimuli were presented at 0 deg and from 10 to 80 deg in the eccentricity with 10 deg step for each of the 8 directions. The constant color name region where the same color name as used at 0 deg was obtained was clearly larger for Y2 and B than those for R and G, while that of Y1 was in between. Approximate size of the constant color name region of monocular viewing extended 30 deg in the nasal and upper, 40 deg in the lower, 70 deg in the temporal visual fields. Outside of the region, the categorical color responses became unstable and in the far periphery achromatic color names such as white or gray often appeared in all of the test stimuli.