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LCD Pixel Checking

Created by dave. Last edited by dave, 13 years and 16 days ago. Viewed 4,840 times. #2
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Buying an LCD?

Explain to the sales droid that LCD displays can have dead (or permanently alive) pixels. It probably won't know that knackered pixels are expected, but the vast majority of displays are perfect, so there's no harm in making sure you get a perfect one. Unpack the display and plug it into a PC in the store. Now you need to check both a completely white screen and a completely black screen - because knackered pixels can be knackered either always on or always off.

An LCD 'turns on' its pixel so it becomes opaque - that is, black. A pixel is 'turned off' (goes clear) and lets the white backlight through it to display white. This is why LCD's are not as good at displaying black as CRT's. The backlight is always on, and the pixels can have varying degrees of opaqueness when turned on. This makes black more of an uneven very dark gray (well, uneven on my LCD anyway..newer ones might be better at it)

To check always off, fire up Internet Explorer, go to "about:blank" and press F11 (full screen). This will give you a page full of white. Scan the page closely looking for "always off" dead pixels.

Then, to test for always on pixels, right click on the desktop and go to screen saver. Select "Blank" and then "Preview". Again, scan the blank screen and this time look for "always on" pixels - although these are much easier to spot!

Then go to javscript:void(document.bgColor='red'), javscript:void(document.bgColor='green'), and javscript:void(document.bgColor='blue') with Full Screen (F11) after each color.

(This note made by mangling a couple of Slashdork posts together)

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