Color appearance of filled-in backgrounds affects hue cancellation, but not detection thresholds.

A long-wavelength background can affect the appearance of an increment of light superimposed upon it in two ways. It can change the visual system's sensitivity to the increment, and it can change the appearance of the increment by directly adding redness to it. Through selective retinal-image stabilization, we evoked the filling-in phenomenon to change the appearance of 640- and 575-nm backgrounds. Either of these backgrounds could be made to appear red or yellow, depending upon whether it was viewed under stabilized or unstabilized conditions. When the appearance of the 640-nm background was altered by filling-in to appear less red, test probes superimposed upon it required less 540-nm component to achieve an equilibrium hue. Increment thresholds measured on the 640- and 575-nm backgrounds, however, did not change with the appearance of the backgrounds.