ABSTRACT
In contrast to persistent images, which contribute to the effectiveness of motion pictures by eliminating fl icker, afterimages tend to interfere with subsequent perceptions. For example, an attempt to read immediately after looking directly at a fl ashtube when it is fi red can be frustrated by the afterimage. When a visual perception is altered by a preceding visual experience, the alteration is referred to as an aftereffect. Whereas the afterimage of a yellow lightbulb tends to appear blue when the gaze is shifted to a gray surface, it tends to appear magenta when the gaze is shifted to a red surface. The perceptual result of mixing a blue afterimage with a red stimulus is similar to that produced by physically mixing blue and red light. If such an experiment is conducted to demonstrate an aftereffect, the viewer will be aware of the altered perception, but viewers are not commonly aware of aftereffects that occur in everyday
life. Brightness adaptation to daylight alters the subsequent perception of the light level in a dimly-lit interior, and it is only when the interior begins to lighten as the visual system adapts to the lower-light level that the viewer is aware of the aftereffect.
