Shift in Rayleigh matches after adaptation to monochromatic light of various intensities.

The action spectrum for inducing a long-lasting protan shift in colour matches was investigated. Rayleigh matches were measured before and after 30 min adaptation to monochromatic light of 520, 550, 580 or 620 nm. For each wavelength, seven retinal illuminances, ranging from 3.0 to 5.0 log td, were chosen in random order. Results for one colour-normal observer show that the shift in Rayleigh match after adaptation increases monotonically as a function of the luminance of the adapting light. The dynamic response range is from 3.3 to 4.7 log td. The wavelength of the adapting light had no systematic influence on the form of the response function. The results imply that the effect is triggered by light absorbed in the photopigments themselves.