Munehira Akita

Maintaining an absolute hue in the presence of different background colors

Abstract Subjects were instructed to make wavelength settings for various hues by an absolute method in the presence of surround-field colors or darkness. Surround- and test-field colors were equated in luminance. The subjects compensatory shift in setting for the maintenance of a test-color is taken to be the difference between his wavelength setting for the test-color in the presence of the surround-field color and the wavelength setting for the test-color with a dark surround. In general, the compensatory shift in wavelength setting is always in the direction of the background wavelength. A discussion regarding the nature of the shift setting is given.

The neon color effect in the ehrenstein pattern: Dependence on wavelength and illuminance

The neon color effect can be described as an illusory spread of color surrounding colored lines embedded in certain line gaps. The effect is seen in the Ehrenstein pattern if colored crosses are added to the central gaps so as to connect the inner tips of the pattern. Experiments were conducted to explore the dependence of this neon color effect on the wavelength and retinal illuminance of the inducing lines. The following results were obtained: neon color effects are strong when the wavelength of the crosses is in the short- (less than 480 nm) or long-wave part of the spectrum (greater than 620 nm) and the wavelength of the Ehrenstein pattern is in the middle-wave part (500-580 nm). Effects are weak or absent when the crosses and the pattern have similar wavelengths. The neon color effect is just detectable when the ratio between the retinal illuminances of the Ehrenstein pattern and the crosses ranges from 0.1 to 0.8. The neon color effect is maximal at illuminance ratios ranging from 0.8 to 8. The strength of the neon color effect is independent of the illuminance level of the crosses if the illuminance ratio to the Ehrenstein pattern is maintained.

Effect of light adaptation on the perceptual red–green and yellow–blue opponent-color responses

Spectral sensitivities of the red-green and yellow-blue opponent-color responses were determined under broad-band light adaptation for the light-adaptation levels of 5 to 5000 Td. With changing light-adaptation level, the spectral-sensitivity functions of the opponent-color systems change in shape, especially in the short-wavelength region of the spectrum. The light-adaptation effect on the red-green responses can be ascribed to the changes at the cone receptor level, whereas the light-adaptation effect on the yellow-blue responses can be ascribed to the changes at two sites, i.e., at the cone receptor site and at the opponent site.

Maintaining an absolute test hue in the presence of different background colors and luminance ratios

Abstract Measures are made of changes in test wavelength required to compensate for a contrast effect introduced by a background color. The test hue remains constant when the contrast effect is modified by a shift of the test wavelength, usually toward the direction of the background. Ratio of test-to-background luminance has an imprecisely specifiable influence on compensatory wavelength changes in the test area. Wavelength settings for similar test hues made in a dark surround at two levels of luminance, 1.1 and 12.0 mL, demonstrate a Bezold-Brucke shift due to intensity level (data of Akita, Graham and Hsia (1964)).

Design and ergonomics

Using both Japanese and American annual design reports the latest industrial product designs are reviewed. The paper concludes that ergonomics plays an important role in unifying high-technology mass products with design for human use and in creating an aesthetic value in products.

Achromatic sensation for trichromatic mixture as a function of stimulus intensity

Abstract Achromatic sensations for trichromatic mixtures were determined as a function of stimulus intensity with the spectral composition as a parameter. The result showed that the change in the achromatic locus with stimulus intensity was described in terms of a linear relation between the middleand long-wavelength components and of a nonlinear relation between the short- and longer-wavelength components.

Red-green opponency in the detection and the perceptual hue cancellation

We show how the red-green antagonism in the detection process is related to the red-green antagonism in the hue cancellation. By measuring the incremental redness or greenness thresholds for bichromatic mixtures, the red-green antagonism was determined at color threshold and in the perceptual hue cancellation. By measuring the detection threshold for bichromatic mixtures, the red-green antagonism was determined at detection threshold. There was agreement among the red-green antagonisms at detection threshold, at color threshold and in the perceptual hue cancellation.

Positive colored afterimages from the figure-ground configurations of colored lights: Effects of chromaticity, luminance and a spatial parameter of the adapting stimuli

Colored afterimages were obtained after the eye was exposed to the adapting field consisting of the figure-ground configuration of colored lights with the same hue and different saturation. When a colored patch was surrounded by a more saturated field, the color of the afterimage was similar to that of the previous patch (positive afterimage). By measuring the threshold chromaticity difference between the patch and the surround for the production of the positive afterimage, the effects of the chromaticity, luminance and a spatial parameter of the adapting field were determined. The obtained threshold chromaticity differences increased with an increase in the saturation of the adapting field, and with a decrease in the surround luminance. When the adapting field consisted of an equiluminous saturation-modulated rectangular grating, the threshold chromaticity difference curves showed similar properties as those of the contrast thresholds for equiluminous chromaticity-modulated gratings. The results suggest the existence of a set of mechanisms at higher-order level in the visual system, tuning the difference in hue and/or saturation across contours.

Nonlinearity of Yellow-Blue Opponent-Color System: Discrepancy Between Deuteranope and Normal Trichromat

The yellow-blue cancellation equilibria were determined, for a deuteranope, as a function of stimulus intensity and wavelength. The resulting cancellation functions were linear functions of stimulus intensity. The linear property of the yellow-blue system in deuteranopic vision has a sharp contrast to the nonlinear property in normal color vision. This difference can be understood if post-receptoral abnormalities of dichromats are considered, specifically lacking the signal which controls the sensitivity of the blue response in normal trichromats.

Analysis of EEG to colored lights by the maximum entropy method

In a color normal male subject, EEGs were recorded while the subject viewed red, green or achromatic lights (14 cd/m2) presented on a CRT, and also in a dark room with the subject being instructed to keep his eyes open or closed. Data analysis was performed by the maximum entropy method (MEM) through which event-related spectral power density (PSD) was obtained with its color topographic brain mappings. Based on the EEG mapping it was shown that cortical activation patterns, in general, exhibited fewer differences corresponding to differences of colored lights stimulation, but distinct changes were found between eye closed and eye open conditions in the dark room.