after-image

Definition: The image or stimulus remaining on a detector after the primary stimulus has been removed. * With the human eye, the after-image usually appears in the complementary colour of the primary stimulus e.g. a bright red spot in the visual field is momentarily seen as a cyan spot when the red spot is removed. * With certain types of exposure meters such as selenium cell, the after-image due to a strong light can render inaccurate a reading of low light levels if taken immediately after the strong light.

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