Simultaneous brightness contrast for flashes of light of different durations.

Measurements have been made of the magnitude of simultaneous brightness contrast on two young adult male observers by a binocular brightness matching method. Five different luminances of the inducing pattern were studied and the duration of the exposure was varied between 5 and 150 msec, along an arithmetic scale. For low inducing flash luminances, the longer exposures show the greater contrast effect. However, as the luminance of the inducing pattern was progressively increased, the duration of exposure showing the largest contrast effect systematically decreased. The curves resemble the Broca-Sulzer curves both in the •manner, at any given luminance, that the ordinate varies with duration and. in the way any given curve changes as luminance is varied. The data explain a previous contradiction between results from psychophysical and. electrophi/siological experiments and therefore greatly strengthen physiological theories of contrast.