LUMINANCE GRADIENTS - PHOTOMETRIC ANALYSIS AND PERCEPTUAL REPRODUCTION

While IESNA RP-24 Lighting makes specific recommendations for ceiling- plane luminance ratios, it does not consider the spatial distribution of luminance and its perception by an observer. This paper proposes lu minance gradients as a more suitable metric, and demonstrates how to m easure them using a CCD video photometer. A related issue is that the average luminance of a luminaire has been shown to be a relatively unr eliable metric for determining the probability of visual glare. This p aper demonstrates ho rv the same CCD video photometer can be used to d irectly measure the luminance distribution of a luminaire, and to prov ide data for more meaningful luminance metrics. Finally, it is known t hat computer-generated synthetic images and photographs of architectur al spaces illuminated by indirect lighting systems often appear visual ly unrealistic. This paper examines the role of luminance gradients, a daptation, and our spatial field of view in the perception of these im ages, and considers spatially nonuniform luminance scaling functions f or computer-generated synthetic and captured video images that compens ate for certain perceptual errors.