Abstract

As the intensity of steady background lights is increased, rod thresholds are elevated, until a level is reached beyond which rod sensitivity is drastically reduced with further increases in background intensity. This phenomenon, rod saturation, occurs at moderate light levels. Rod saturation occurs at lower background levels when backgrounds are flashed, that is, when there is no pre-adaptation period (e.g. Adelson, 1982). Alexander and Kelly (1984) have shown, by taking advantage of the Stiles-Crawford effect and by testing protanopes, that long-wavelength sensitive cones (LWS) contribute to rod saturation on flashed backgrounds, reducing the background intensity required to produce saturation. In fact, rod thresholds are higher on flashed than steady backgrounds at levels well below saturation.

© 1990 Optical Society of America