Loginovich Y, Bulatov A, Bertulis A, 2005, "Contrast influence on binocular fusion limits" Perception 34 ECVP Abstract Supplement
Contrast influence on binocular fusion limits
Y Loginovich, A Bulatov, A Bertulis
Panum's area in the foveal region was examined with paired three-dot stimuli organised in right-angle patterns displayed separately to each eye. The length of the sides of the stimuli was 20 or 30 min of arc. In the experiments, subjects manipulated by the panel keys and pushed one end-dot of the test stimulus horizontally to the left or to the right and vertically up or down in 0.3 min of arc steps until reaching the fusion limits. The background luminance was 10 cd m-2; the luminance of the reference dots was 50 cd m-2; and the test-dot luminance was varied from 20 to 50 cd m-2. Panum's area was found to have an ellipsoidal shape with the ratio of diameters roughly constant, 1:2 for all luminance values tested. The size of the area did not vary with the test-dot luminance changes within the 35 - 50 cd m-2 range and it increased regularly with luminance decrease below 35 cd m-2 until reaching the dot-detection threshold at about 22 cd m-2. The test-dot luminance below the background level made the test-dot appear black and disabled binocular fusion. According to Herring's law, variability of Panum's area size with luminance changes may be interpreted as a weighted averaging of monocular visual directions.
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