Rod–cone mechanism underlying the Purkinje shift

Abstract

TABLES have been published¹ of averaged brightness matches made by 16 observers who had compared 11 spectral lights (from 410 to 710 nm) with the CIE standard radiator in a 15° field set at various levels in the mesopic range. The scotopic and photopic luminances (S,P) of each light were calculated by multiplying the spectral radiant power for the match by the corresponding values of the CIE V′ and ȳ₁₀ functions, with appropriate weighting factors. ȳ₁₀ was used because of the large field. The spectral data can readily be converted to the usual CIE system, and in fact the choice is immaterial in the following argument. As the matches were mesopic, neither S nor P alone can represent the luminance, and the Tables were used later² to define this quantity as a function of (S,P). Arithmetic manipulation of the data now suggests a simple rod–cone mechanism responsible for the sensation of brightness.