BRIGHTNESS PERCEPTION FROM SOURCES OF NONUNIFORM LUMINANCE

This paper presents additional data from a research study related to t he perceived brightness of sources of non-uniform luminance. Compariso ns are made to previously reported data on discomfort glare ratings ba sed on the same sources.This study was performed using sine and square wave gradients as the non-uniform luminance stimuli. For each non-uni form stimulus, 12 subjects made paired comparisons using a series of u niform stimuli until an equivalently bright uniform stimulus was found . Results of this study suggest significant perceptual differences bet ween uniform and non-uniform sources. The major variable affecting the se differences is the position of the source in the field of view Non- uniform stimuli are perceived as brighter than uniform sources when th e observer is fixated on the stimulus, while being perceived as less b right than uniform sources when die stimulus is in the periphery of th e observer's field of view When comparing this study to the previously published discomfort study, brightness perceptions are highly correla ted to the level of discomfort glare and have less variance than the d iscomfort study.