ABSTRACT

This chapter summarizes some aspects of contrast vision, its limits, and what can be gained by contrast adaptation. The neural mechanisms mediating contrast vision should take into account that retinal image contrast is generally very low at high spatial frequencies, which contain the information about fine details and are therefore of particular importance for high visual acuity. Contrast vision—the ability to distinguish potentially tiny differences in luminance between adjacent positions in the visual scene, or in time—starts already at the first synapses in the visual system that connects rods and cones to bipolar and horizontal cells. There are two major variables to describe contrast: Michelson contrast and A. Weber contrast. Spurious resolution also needs to be taken into account when contrast adaptation is studied under defocus because there may be little adaptation at the spatial frequencies where the contrast sign reversal occurs.