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Old 01-23-2018, 10:14 AM
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Quote:
Originally Posted by N2IXK View Post
Nice video. I was surprised to see how short the phosphor persistence actually is, fading out after 2-3 scan lines. MUCH shorter than I thought compared to the visual persistence of the viewer's eyes.
Most of the glow is gone within a few microseconds. However, the glow has such a long tail-off (even slower than exponential in most cases) that this short decay is necessary to prevent visible trails following bright objects. Some CRTs did not meet this criterion, and you could see white trails following scrolling white titles on a black background. The first large screen high definition displays available to researchers were Hitachi rear projos, which had notoriously slow decay of the long tail.

Rough calculation: Suppose half the light is gone in one microsecond. This means that during that microsecond the spot is approximately 17 THOUSAND times brighter than the average brightness of the picture (which lasts 1/30 of
second); so, due to the dynamic range of the eye, the afterglow needs to be only about 1/100 of the average to be visible, or about one two-millionth of the peak.
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