[danielf]

Originally Posted by Hugh

To be more precise, perfectly true.

Positive and Negative After Images are both examples of Persistence of Vision...

Not really...

The myth of persistence of vision is the belief that human perception of motion (brain centered) is the result of persistence of vision (eye centred). The myth was debunked in 1912 by Wertheimer[1] but persists in many citations in many classic and modern film-theory texts.[2][3][4] A more plausible theory to explain motion perception (at least on a descriptive level) are two distinct perceptual illusions: phi phenomenon and beta movement.

http://en.wikipedia.org/wiki/Persistence_of_vision


Afterimage

Negative afterimages are caused when the eye's photoreceptors, primarily those known as cone cells, adapt from the overstimulation and lose sensitivity.[1] Normally the eye deals with this problem by rapidly moving small amounts (see: microsaccade), the motion later being "filtered out" so it is not noticeable. However if the color image is large enough that the small movements are not enough to change the color under one area of the retina, those cones will eventually tire or adapt and stop responding. The rod cells can also be affected by this.[citation needed]

When the eyes are then diverted to a blank space, the adapted photoreceptors send out a weak signal and those colors remain muted. However, the surrounding cones that were not being excited by that color are still "fresh", and send out a strong signal. The signal is exactly the same as if looking at the opposite color, which is how the brain interprets it.[citation needed]