2 - Light, the Retinal Image, and Photoreceptors

Abstract

This chapter discusses the sequence of events, beginning with the stimulus that ultimately leads to the generation of signals in photoreceptors. All quantitative analyses of human visual performance, whether in the domain of color vision or otherwise, require meaningful ways to describe the light stimulus. The number of descriptions from which to choose is large. The appropriate description to use in a given situation depends on such factors as the spatial, temporal, and spectral properties of the stimulus. It also depends on whether one wants to provide a purely physical description of the stimulus or take into account known properties of human vision to estimate the visual effect of the stimulus. The chapter discusses the physical attributes of the light emanating from the object that are important for human vision. It examines the transmittance of light through the optics of the eye and the formation of the retinal image. Finally, it discusses the sampling of the light distribution in the retinal image by the mosaic of photoreceptors.