after-image


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Related to after-image: positive afterimage

af·ter·im·age

, after-image (af'tĕr-im'ăj)
Persistence of a visual response after cessation of the stimulus.

after-image

A visual negative impression of a bright object or light, which persists for a few seconds after the gaze is shifted or the eyes closed. Persistence of a positive image after moving the eyes implies a potentially serious neurological defect.

after-image 

Visual sensation persisting after the original stimulus has been removed. If observed in darkness following stimulation by a high intensity, brief duration light source, seven different after-image phases are frequently noted. The first phase, also called Hering's after-image, is a positive after-image and it is followed by a negative after-image. After a short interval (less than half a second) a second positive after-image, called Purkinje after-image or Bidwell's ghost, appears, the character of which depends upon the conditions of adaptation, the colour of the stimulus and the retinal region stimulated (best in the periphery). Afterwards, a second negative after-image is sometimes observed followed by a third positive after-image, called Hess after-image. After a long dark interval, a third negative after-image may appear followed after another long dark interval by a fourth positive after-image. If the light stimulus is of moderate intensity, the last phases will be absent. See Emmert's law; after-image test; after-image transfer test.
complementary after-image An after-image in which the colour is complementary to the colour of the original stimulus.
Hering's; Hess after-image See after-image.
homochromatic after-image An after-image in which the colour appears the same as in the original stimulus.
motion after-image See waterfall after-effect; Plateau's spiral.
negative after-image An after-image in which the light areas of the original stimulus appear dark, the dark areas appear light and the coloured areas appear in a complementary colour.
positive after-image An after-image that appears the same as the original stimulus.
Purkinje after-image See after-image.
References in periodicals archive ?
This first-of-its-kind optometry center treats a variety of visual ailments striking computer users, particularly a phenomenon called McCullouch after-image where users see images bathed in pink whenever they look away from the computer screen.
Sharp motion capability with high response speed of less than 8ms1 for response time and limited after-image
His red painting on MDF, lit from the back by neon, pulses on the wall like a shadowy after-image.
Now focus on the after-image - the picture you have of the bulb once you close your eyes - until it vanishes completely.
Rather than being exposed to the light, the real power you get from this exercise comes from focusing on the after-image which remains etched on your retina.
Some of your films, in fact, have left me with a curiously spherical mental after-image.
Mosaic sidewalks phase the downcast vision, And where it lifts, the solid dome has pulse - As if that after-image, wholly motion, Unfettered structure from the space it fills;
He denies her the space to be part of the freedom he is envisioning for himself, because his concept of freedom is an after-image of desire.
In After-Images of the City, Joan Ramon Resina, Dieter Ingenschay, and other scholars have entered this area of inquiry by making a case for viewing the "urban image" from the perspective of change.