Abstract
PURPOSE: A new technique for establishing very-long-term (VLT) chromatic adaptation (over days and weeks) was assessed and compared to the classical approach. Shifts in equilibrium yellow were measured following VLT adaptation to either long-wavelength room illumination for several hours per day (classical paradigm) or to a long-wavelength CRT pattern for 1 hour per day. The aim was to test whether the briefer CRT pattern produced VLT chromatic adaptation comparable to that invoked by longer-lasting illumination.
METHODS: (a) Both means of adaptation used a long-wave reddish-appearing light. In the classical condition, the subject spent 4 hours/day in a windowless room in which overhead light passed through a filter that allowed only 5% transmittance of wavelengths below 540nm (Judd x = 0.408, y = 0.420). In the new method, the subject viewed a moving grating composed of only the R phosphor of a CRT monitor (Judd x = 0.598, y = 0.345) for 1 hour per day. [We thank Dr. J. Neitz of the Medical College of Wisconsin, who suggested this approach to us.] (b) Measurements to assess color perception were performed either 22 hours (CRT) or 19 hours (room illumination) after the most recent adapting period. The subject set an admixture of 540nm-plus-660nm light to appear equilibrium yellow at 4 luminance levels between 3 and 100 trolands.
RESULTS: Both methods of chromatic adaptation produced VLT shifts in the chromaticity of equilibrium yellow as well as similar shifts back toward baseline during the 2-week post-adaptation recovery period.
CONCLUSION: Viewing a chromatic grating for 1 hour/day produces very-long-term chromatic adaptation. The CRT adapting stimulus has the following advantages over room illumination: the VLT adapting stimulation can be (1) retinotopically localized, (2) dichoptic (unequal in the two eyes) and (3) precisely controlled with respect to chromaticity and cone stimulation.