Abstract

Red-green color discrimination thresholds were measured at 25° in the nasal retina during the cone plateau following a bleach and after 30 min of dark adaptation. Thresholds were obtained for four test colors ranging in appearance from green to red with five circular stimulus fields ranging in size from 1° to 16° in diameter. Thresholds for all test colors decreased with increases in field size both during the cone plateau and after dark adaptation. Thresholds obtained after dark adaptation were always higher than those obtained on the cone plateau. The increase in threshold was typically greatest for green and yellow test colors and least for orange and red. Results on the cone plateau were described well by the Boynton and Kambe equation for red-green thresholds. Dark-adapted thresholds could also be described by adding a term representing rod excitation to this equation.

© 1992 Optical Society of America