Luminance gradient for evaluating lighting

Abstract

This paper introduces luminance gradient as a metric for evaluating common non-uniform luminous environments. Luminance gradient is defined as the largest change rate and the polarity of spatial luminance variation on a large surface or across the entire field of view in high resolution. The metric, a visualization method, and a freely available MatLab code for plotting luminance gradient maps have been developed. The retinal resolution of pixels for mapping luminance gradient has also been identified. A camera-aided measurement method of luminance gradient is proposed, which is demonstrated in two case studies of the evaluation of different types of luminous environments. Moreover, this study explored whether luminance gradient could also be obtained from computer simulations using lighting software programs AGI32 and HeliosPro.