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Does a screensaver save the computer display screen?
And if it does, what does it save the screen from?
If the above two questions have a NO answer, than why is it called screensaver?

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This is a summary of Wikipedia:Screen burn-in.

CRT, Plasma, and OLED displays

These displays develop burn-in due to degradation of the light emitting compounds. Screensavers were initially designed to prevent phosphor burn-in in cathode ray tube (CRT) monitors. Plasma displays are also susceptible to burn-in due to overheating of the phosphors. Organic light-emitting diode (OLED) displays develop burn-in due to degradation of the organic compounds. (cnet)

In the worst cases, the burn-in is visible even when the display is not powered:

enter image description here

LCDs

Liquid crystal displays (LCDs) can suffer a different type of burn-in (gizmodo) also referred to as image persistence (fujitsu). Liquid crystals are designed to allow light through in their relaxed state, but can become "stuck" at a particular level of activation, causing an effect that looks very similar to traditional burn-in. (ref)

Screensavers

Screensavers can be useful in preventing burn-in on CRT, plasma, and OLED displays. For LCD displays, image persitence can be prevented by using a screensaver. (fujitsu)

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    I understand the mechanism on LCD and OLED (light emitting chemical will "wear out" via photochemical side reactions. But what is the mechanism on LCDs? Is there any evidence of a real effect at all? – matt_black Oct 6 '13 at 11:11
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    Does a moving screensaver have any advantage over simply making the screen dark? – gerrit Oct 6 '13 at 11:14
  • @matt_black I attached an image of an LCD suffering image persistence, but I can add referenced details about the mechanism. Thanks. – user5582 Oct 6 '13 at 15:56
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    @gerrit Not that I can tell. – user5582 Oct 6 '13 at 17:07
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    A moving screensaver prevents burn-in by not having the same pixels lit continuously, but makes it easy to tell that the screen is turned on. A "black" screensaver might make you accidentally power cycle when you come up to a computer and think it's turned off. – Larry Gritz Oct 10 '13 at 20:54

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