Spatial sensitivity of the human visual system under selective chromatic adaptation: shape of the contrast sensitivity curves, foveal versus peripheral vision

Abstract

The authors investigated the shape of the contrast sensitivity function of the human visual system for red, green and blue stimuli under selective chromatic adaptation, and, at eccentricities of 0 degrees , 13 degrees and 26 degrees . The results are compared to those obtained for an achromatic test, at the same eccentricities. The stimuli (diameter 8 degrees ) are sinusoidal grating patterns presented steadily or with a phase inversion at temporal frequencies of 2 Hz and 8 Hz. The threshold is determined by an ascending adjustment method. In foveal vision, the bandpass character of the sensitivity function has been brought to light for the three selective chromatic adaptation situations. The bandwidth and optimal frequency are different for the four stimuli: white, red, green and blue test lights, allowing for the chromatic adaptation level reached. In peripheral vision, the bandpass character is strengthened. The red and green curves tend to merge, reflecting either a change in the selective chromatic adaptation with eccentricity or a different evolution of the spatial frequency filtering properties for the three mechanisms with eccentricity. The authors suggest an interpretation of the shape changes of the contrast sensitivity curves, based on the neurological properties of achromatic and chromatic mechanism.