Mesopic spectral luminous efficiency functions:

Final experimental report

Abstract

Spectral luminous efficiency functions in the mesopic range were measured for 24 subjects by the direct brightness matching method in a foveal 10° field covering a range from 100 to 0.01 Td of the adaptation level. The mean functions based on the 24 subjects were presented as the fundamental data set for the development of a mesopic photometric system. The mean functions showed a smooth and continuous change from the photopic-type function to the scotopic-type with the reduction of retinal illuminance. The Individual differences were fairly large throughout the level investigated. The empirical formula proposed in an earlier report was found to be useful to describe the mesopic function at any level.