Hutchinson S J, Logvinenko A D, 2001, "Equiluminance produces the strongest high-spatial-frequency tritanopic effect" Perception 30 ECVP Abstract Supplement
Equiluminance produces the strongest high-spatial-frequency tritanopic effect
S J Hutchinson, A D Logvinenko
High-spatial-frequency tritanopia (HSFT) occurs when the colour appearance of a high-spatial-frequency periodic pattern changes, owing to the differential drop of contrast sensitivity for the receptor colour channels (Logvinenko, 2001 Perception 30 223 - 232). We studied how the HSFT effect depends on luminance contrast. An asymmetric colour-matching technique was used to measure appearance of a horizontal grid of grey diamonds (5 cycles deg-1) inserted into a (i) yellow, (ii) pink, or (iii) alternating yellow/pink background. The patterns were displayed on a Barco colour monitor driven by a VSG 2/3 board. Observers adjusted the uniform (matching) patch beneath the pattern to appear the same colour as the grid by using a keypad to control independently hue, saturation, and brightness of the matching strip. Luminance of the test diamonds was varied (10 - 40 cd m-2) while luminance of the background remained the same (25 cd m-2). Three observers made five measurements for each test colour. Observers' matches were expressed in terms of S-component of the match. For the test diamonds on the pink background, S-component was highest (indicating a saturated blue perception) for equiluminant conditions, while it decreased monotonically (colour became less saturated) the further the pattern was from equiluminance. Although S-component was lowest (saturated yellow - green perception) at equiluminance for test diamonds on the yellow background, change in S-component as a function of test/background luminance contrast was not as pronounced as for the diamonds on the pink background. Results suggest that spatial processing of the colour signal in the S-cone channel is affected by the M- and L-cone channels. Our results are in line with those obtained by Brainard and Williams (1993 Vision Research 33 105 - 116) who showed that the tritanopia of the central foveola effect was reduced by introducing a test/background luminance contrast.
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