Perception of green and red under chromatic adaptation: the effects of stimulus size and eccentricity.

We measured thresholds for the perception of green and red light added to white, blue, green, yellow, or red adaptation fields presented at eccentricities of 0 to 70 degrees in the temporal visual field of two subjects. A series of stimulus sizes was used at each eccentricity to determine size-scaling factor E2--the eccentricity at which stimulus diameter has to be doubled in order to maintain foveal performance. For green light added to white or yellow, E2 varied from 3.1 to 41.5 degrees. When red light was added to white, yellow, or blue, E2 varied from 0.1 to 11.8 degrees. For red color in green and green color in blue or red there was no spatial scaling factor that would make performance independent of eccentricity. Our results suggest that E2 value for green and red perception depends on the state of chromatic adaptation and also shows marked interindividual differences.