Very-long-term and short-term chromatic adaptation: are their influences cumulative?

Abstract

Very-long-term (VLT) chromatic adaptation results from exposure to an altered chromatic environment for days or weeks. Color shifts from VLT adaptation are observed hours or days after leaving the altered environment. Short-term chromatic adaptation, on the other hand, results from exposure for a few minutes or less, with color shifts measured within seconds or a few minutes after the adapting light is extinguished; recovery to the pre-adapted state is complete in less than an hour. Here, both types of adaptation were combined. All adaptation was to reddish-appearing long-wavelength light. Shifts in unique yellow were measured following adaptation. Previous studies demonstrate shifts in unique yellow due to VLT chromatic adaptation, but shifts from short-term chromatic adaptation to comparable adapting light can be far greater than from VLT adaptation. The question considered here is whether the color shifts from VLT adaptation are cumulative with large shifts from short-term adaptation or, alternatively, does simultaneous short-term adaptation eliminate color shifts caused by VLT adaptation. The results show the color shifts from VLT and short-term adaptation together are cumulative, which indicates that both short-term and very-long-term chromatic adaptation affect color perception during natural viewing.

Figure 1

(a) The two consecutive experimental time periods during which equilibrium yellow measurements were obtained. (b) The daily cycle of testing, VLT adaptation and normal viewing. The daily cycle for each observer began at approximately the same time each day throughout the experiment.

Figure 2

(a) Example of CRT display for very-long-term chromatic adaptation (see text). (b) Test stimulus presentation sequence for conditions that included short-term chromatic adaptation (see text).

Figure 3

Average measurements of equilibrium yellow during the baseline and very-long-term chromatic adaptation experimental periods. Baseline measurements: dark adaptation (solid line) and short-term chromatic adaptation alone (dotted line). Shifts in unique yellow due to introducing very-long-term adaptation: VLT adaptation alone (dashed line); VLT together with short-term adaptation (dash-dot line). The amount of 660 nm test light (vertical axis) needed to establish equilibrium yellow is given as a function of the amount of 540 nm test light (horizontal axis).