Chromatic perceptive field sizes change with retinal illuminance

The effect of retinal illuminance (0.3–3.3 log td) on chromatic perceptive field size was investigated at 10° eccentricity along the horizontal meridian of the temporal retina. Using the 4+1 color-naming procedure, observers described the hue and saturation of a series of monochromatic stimuli (440–660 nm, in 10-nm steps) of various test sizes (.098–5°) after 30-min dark adaptation. Perceptive field sizes of the four elemental hues and the saturation component were estimated for each wavelength at each retinal illuminance. Results indicate that perceptive field sizes for blue, green, yellow, and saturation all decrease with increasing retinal illuminance; the perceptive field size for red is the smallest and invariant with intensity. The influence of rods on perceptive field size may account for some of the results; other factors are also considered.