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A stupid Question about dead pixels (1 Viewer)

mhc100g

Auditioning
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Jul 6, 2008
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Real Name
Mike
Hello,
Kind of an amateurish type question for everyone.
I have a Sony Pearl projector and a DA-Lite Perm-Wall high power fixed screen that I am using in my theater room.
I have noticed lately that I see a couple of pixels that are white in the screen when I am watching HD TV. I have tried to replicate it when the Xbox360 is on but I have not yet been able to do it.
Is this caused by the Sony Projector or is it caused by the screen that I am viewing it on?

Thanks,
Mike
 

Allan Jayne

Senior HTF Member
Joined
Nov 1, 1998
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2,405
If a suspected dead pixel is white on the screen, it may or not be white all the time. With most LCD or LCoS projectors, three picture generating panels contribute to the picture and if just one of the panels has a dead pixel, the color of the affected location will depend on what color that spot should really be namely what the other two panels are contributing as well.

One short example: The red panel has a pixel stuck on.

If the color patch in that area is bright red, yellow, magenta, or white, you will not see any defect since the red pixel is supposed to be on anyway. If the color patch is supposed to be black, you see a tiny red spot within. If the color patch is supposed to be green, you see a yellow spot. If the color patch is supposed to be blue, you see a magenta spot. If the patch is supposed to be cyan, you see a white spot.

Or maybe you are lucky and there is nothing wrong with the projector, you are seeing a defect in the source material.

Move the projector slightly when you see the "dead pixels". If the "dead pixels" don't move with the picture, then you just have stray light hitting the screen or a screen defect. Minute screen defects can reflect back a tiny bright spot which will not always be white but may be bright enought to look white in the color patch you are viewing.

Video hints: Video Technicalia Made Easy
 

chuckg

Supporting Actor
Joined
Apr 27, 2004
Messages
921
If you see a pixel on with TV, but no pixel on with the Xbox, then I would suspect the TV signal. I have seen news broadcasts with stuck pixels, for example. I'm guessing it is their camera or their processing equipment.
 

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