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 ?
Poems on such after-images are poised between doubt and hope, frequently interrogative and marked by a sense of their own improbability.
Woods, provide useful instances of the dynamic life of the "after-image" in the historical developments that have transformed the city.
Resina's essay, "From Rose of Fire to City of Ivory," also illustrates the usefulness of the concept of the "after-image" in deciphering the processes by which the Spanish state and generations of Barcelonans engaged in conflicting efforts to manifest their vision of the city.
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.
His red painting on MDF, lit from the back by neon, pulses on the wall like a shadowy after-image. There's also an architectural model for a "Meditation Space" (1998): a glass structure with red circles on its surface,Formal elements as material metaphors of focus, clarity and reflection.
You might be familiar with the effect already - try staring at the sun and then close your eyes - it leaves an 'after-image' that can still be seen for several moments afterwards.
OEL displays react quickly with no lingering after-image. The material itself glows, precluding the need for a backlight as is needed with LCDs.
LS: In both your films and your rhetoric, you make frequent reference to the "confinement of the circle" and the "unexplored possibilities of the sphere." 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.
The book's whole argument is directed towards the speculative claim that, after the long haul to modernity: |the modern work of art itself in its unity without a principle or concept determining that unity, and the community gathered around particular works with their shared sensus communis, became images or after-images of the (idealized) polis.