Abstract

We examined the effects of luminance contrast and spatial frequency on chromaticity discrimination of grating bars. The apparatus was a computer-controlled Maxwellian view stimulator with a 2-mm artificial pupil. The 2° square-wave gratings ranged from 1.07 to 8.6 cpd. Alternate bars were filled with light of a standard wavelength and light that could be varied in wavelength with a monochromator. The variable bars were set 0.2, 0.1, 0.03, or 0.0 log unit brighter or dimmer than the standard. The observers’ task was to match the variable bars to the standard bars in hue. Discrimination, as measured by the standard deviation of the matches, was poorer at higher spatial frequencies. There was no statistically significant difference of discrimination in the equal and unequal luminance conditions at a given spatial frequency, implying that luminance contrast did not improve chromaticity discrimination. However, luminance contrast did lead to Bezold-Brucke hue shifts that were spatial frequency dependent.

© 1985 Optical Society of America