Retinal persistence
The retinal Persistance is the capacity or defect of the eye to preserve an image seen superimposed at the images that one is seeing. It is stronger and longer if the image observed is luminous. This is due partly to the biochemical processing time of the signal Optique. One distinguishes two types of retinal persistence:
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the positive persistence, which lasts little of time (approximately 50 milliseconds) and which is color of the image which persists (example: a flash does not even last thousandths of second but one can see it much longer enlightened).
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the negative persistence, which lasts longer. It is due to an exposure prolonged to a strong luminous intensity. One keeps then printed a dark trace of the image in the vision during several seconds (example: the trace of the sun after having closed the eyes).
Retinal persistence and illusion of continuity
See also: Vision
On a television set, the image seems stable, it does not flicker. However the screen emits the images only intermittently (see Entrelacement). The explanation by retinal persistence is tempting but does not seem to be enough to explain the illusion of continuity. The absence of information between the images would be simply too short so that the brain does not notice something. This principle is used in the cinema.
External bond
- the brain on all the levels - Vision and cinema
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