Does melanopsin help to explain color constancy in natural environments?

Abstract

The aim of this work was to assess whether melanopsin excitation could help to achieve a better color constancy in natural environments. Data from hyperspectral natural images and 21 daylight illuminants were used to compute L-, M-, S-cone and melanopsin excitations for each pixel. The geometrical distance in the cone chromaticity diagram [L/(L+M) and S/(L+M)] was computed between daylight illuminants and the reference illuminant (D65) for each pixel in each image. These distances were related to melanopsin excitation. Our analysis showed that to achieve a better color constancy, melanopsin contribution to afferent chromatic pathways depends on the correlated color temperature (CCT) of illuminants. For CCT values related to clear sky conditions, signals in the S/(L+M) axis need a positive melanopsin contribution, and the L/(L+M) axis a negative contribution. Instead, scenes such as those related with dawn and dusk, have worse constancy when melanopsin is considered.