Effects of luminance on the perception of red and green at various retinal positions.

Abstract

The red–green ratios corresponding to the perception of red or green were determined by use of the method of constant stimuli. At three luminance levels (0.3, 0.1, and 0.01 ft-L), measurements were made with a 1° stimulus centered foveally, and at 2°, 6°, 10°, 14°, and 18° along the upper vertical meridian. At the two highest luminance levels, red sensitivity as measured by red-green ratios appeared constant from 2° to 14° and then decreased at 18°. Green sensitivity remained much the same from 2° to 10° and then dropped off sharply. At the lowest luminance level, green sensitivity was lost completely beyond 2° and there was a progressive decrease in red sensitivity as the peripheral angle increased. With decreasing luminance and increasing peripheral angle, variability of the red–green ratios required for the perception of red and green increased.