Modelling Contrast Sensitivity for Chromatic Temporal Modulations

Abstract

The temporal contrast sensitivity to isoluminant chromatic flicker was measured for three observers using the method of adjustment. The isoluminant stimuli were created for each observer individually, based on a technique similar to heterochromatic flicker photometry. The chromatic flicker stimuli were sinusoidal modulations, defined in the CIE 1976 UCS (u', v') chromaticity diagram. The chromaticity varied around a base color along a certain modulation direction with a certain amplitude at a certain frequency. Nine base colors, four modulation directions and seven frequencies were used, resulting in thirty-six temporal contrast sensitivity curves per observer. An exponential model was fitted to the resulting contrast sensitivity expressed as 1/Δ(u', v'), 1/ΔLMS and 1/Δlms. The model resulted in an average R2 value higher than 0.93 for the three different measures of contrast sensitivity. The two parameters of the model (i.e. the slope β1 and intercept β0) were found to significantly depend on the base color and direction of the chromatic modulation. This means that Δ(u', v'), ΔLMS and Δlms are not suitable measures to predict the sensitivity to temporal chromatic modulations in different locations of the color space.