EVIDENCE FOR THE EQUIVALENT-BACKGROUND HYPOTHESIS IN CONES

The equivalent-background hypothesis was tested in the cone system for increment-field diameters of 3.5′, 10′ and 50′. The wavelength composition of the increment field was also varied; it was either white (color temperature 3000 K) or red (657 nm). The dark-adaptation thresholds were obtained following full bleaches. Using an analysis which corrected all the data for the effects of photopigment depletion, the equivalent-background hypothesis was found to hold fairly accurately across all conditions. The results suggest that the long-term adaptation mechanisms in the rod and cone systems are very similar. © 1979.