Abstract
Abstract: :
Purpose: We propose a mathematical model to derive the chromatic parameters from increment–threshold spectral sensitivity functions. We applied this model to determine the effective red, green, blue and yellow mechanisms’ contribution to the detection of spectral stimuli of five normal, thrichromatic subjects. Methods: Using a standard spectral sensitivity setup mounted on an optical bench, consisting of a Xenon arc lamp with a monochromator the detection thresholds were measured for a 300–ms, 1o circular test flash presented on a 100–cd/m² white background, for spectral wavelengths between 410 and 660 nm. Results:The model analysis confirmed that in the red–green wavelength area, the detection of our chosen stimuli was mediated by two distinct (L–M) antagonistic mechanisms. The first L–M antagonistic mechanism, can be identified with the red–green mechanism according to what is currently understood regarding retinal physiology. We inferred that the red–green mechanism receptive fields consisted of a single L– or M–cone center with a homogeneous or heterogeneous surround devoid of S–cone projections. On the other hand, modern physiological studies do not predict a second L–M antagonistic mechanism with the maximal sensitivity in yellow wavelength zone. Our data point to the presence of L–M antagonistic system for yellow mechanism. The receptive fields of the yellow half of the blue–yellow mechanism, consisted of a L– or M–cone center with a homogeneous or heterogeneous surround configuration but with S–cone projections present in the surround. This proposal is not concordant with what is currently understood regarding retinal physiology. Conclusions: We argue that two different (L–M) antagonistic mechanisms represent the best alternative for designing a color receptor system with even color detection through three channels (such as red, green and yellow) from two broadband spectral sensitivity receptors such as L– and M– cones.
Keywords: color vision • color appearance/constancy • photoreceptors: visual performance