A Comprehensive Quantitative Method for Prediction of Visual Performance Potential as a Function of Reference Luminance

Abstract

This article describes the quantitative method for prediction of visual performance potential as a function of reference luminance which has been developed from the results of studies described in four earlier articles of the present series. The method involves two nonlinear transforms, the first relating visibility metrics to reference luminance for different task conditions, the second relating visual performance potential to visibility metrics. The new first transform metric designated visibility is introduced which will be useful in defining indices of visual effectiveness of lighting, namely equivalent reference luminance and equivalent reference illuminance. These indices may be used to evaluate lighting systems differing with respect to the level of task luminance they provide, the geometry and polarization of illuminance, and the degree to which the luminance of the visual field is uniform. Visibility level is a second metric of the first transform which may be used as an alternate to visibility. The second transform is described in terms of processes which include the visual sensory process revealed by studies of the five Landolt ring visual performance reference task, and two oculomotor processes involved in the maintenance of steady ocular fixation and the control of rapid and accurate saccadic eye movements. A quantitative model consisting of the two transforms may be used in setting standards for illuminance levels and in conducting cost-benefit analyses of lighting.