Testing the CIE system for mesopic photometry in a threshold detection experiment

Abstract

Results from a mesopic threshold detection experiment using static, quasi-monochromatic, 2° incremental detection targets were used to test the International Commission on Illumination (CIE) recommended system for mesopic photometry based on visual performance. An experimental apparatus was built to produce different mesopic backgrounds (four different spectral compositions at two different luminances, 0.1 cd/m² and 1.0 cd/m²) on which the targets were projected at different eccentricities (2.65° and 10°). The CIE system was tested by two methods, variability of mesopic threshold contrast for different target chromaticities and trend analysis for mesopic threshold contrast plotted against background mesopic luminance. The mesopic threshold contrast did not remain constant among the different target centroid wavelengths within a given viewing condition. The inter-observer variability of the mesopic contrast threshold dataset was considerable.