Differential luminance sensitivity of the human visual system

Abstract

In this paper the differential sensitivity of the visual system is investigated by means of two simultaneously presented stimuli in a yes-no procedure. The sensitivity measure σ I appears to be proportional to stimulus intensity (i.e., Weber's law). The curve displaying Weber's law is little affected by variation of the background intensity or of the adaptation level. An increment threshold experiment using only one stimulus yields a proportionality of σ I with the square root of the background intensity. An additional experiment shows that the sensitivity measure σ I for two flashes decreases first, from dark up to a particular background intensity, and increases when the background tends to mask the flashes. So, in general, two background levels exist with the same differential sensitivity. The results cannot easily be explained by the simple quantum fluctuation concept. A model based partially on electrophysiological data from the literature is proposed which encounters a particular adaptation mechanism, a transducer with a limited dynamical range, and a range setting mechanism. © 1971 Psychonomic Journals, Inc.