Effect of Surround and Stimulus Luminance on the Discrimination of Hue

The effects of changes in the luminance of the stimulus and the surround on hue discrimination were experimentally investigated, using the method of constant stimuli. All observations were made at 550 mμ; the standard deviation was used as the measure of sensitivity. Surround luminance was found to have no effect on hue discrimination until the surround had three or more times the luminance of the stimulus. As the surround to stimulus ratios increased, the threshold rose sharply. Increase of the stimulus intensity over a range of 1.5 log units from the photopic threshold increased the discrimination threshold by an average of only about 2 mμ.