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An afterimage, or after-image, is an image that continues to appear in the eyes after a period of exposure to the original image. An afterimage may be a normal phenomenon (physiological afterimage) or may be pathological ( palinopsia ).
Under a phenomenon known as the ‘negative picture illusion’, a negative image can be briefly experienced by the human visual system where an afterimage persists subsequent to a prolonged gaze. Film negatives usually have less contrast, but a wider dynamic range , than the final printed positive images.
A stimulus consistently produces the same afterimage, which is dependent on the stimulus intensity and contrast, the time of fixation, and the retinal adaptation state. Physiological afterimages are usually the complementary color of the original stimulus ( negative afterimage ), while palinoptic afterimages are usually the same color as the ...
They argued that with gratings, prolonged fixation of the stimuli builds up a negative afterimage that will tend to cancel the real images, making both invisible (a form of neural adaptation). An eye movement at right angles to one grating of one half of the period of the grating will make the afterimage reinforce that original image, making it ...
This theory also explains negative afterimages; once a stimulus of a certain color is presented, the opponent color is perceived after the stimulus is removed because the anabolic and catabolic processes are reversed. For example, red creates a positive (or excitatory) response while green creates a negative (or inhibitory) response.
The study supplies two experiments. In the first experimental study, one eye was stimulated with a colored patch on a white background while the other eye remained closed. After sometime, when the covered eye was uncovered, a negative after-image was perceived by the unstimulated eye.
The observer then perceives a cyan (or magenta) square on the blank sheet. This complementary color afterimage is more easily explained by the trichromatic color theory (Young–Helmholtz theory) than the traditional RYB color theory; in the opponent-process theory, fatigue of pathways promoting red produces the illusion of a cyan square. [39]
Lesions in the visual pathway affect vision most often by creating deficits or negative phenomena, such as blindness, visual field deficits or scotomas, decreased visual acuity and color blindness. On occasion, they may also create false visual images, called positive visual phenomena.