Dead Pixels
 

Well, this question is sparked from another thread don the board...

But what is a dead pixel? How can you tell if you have one? Just wondering...

Joshua,

Read the survey someone did on Google News Groups...

http://tinyurl.com/ig6z

That should explain it a bit!

Cheers,
Jack

You can tell is you have one by diplaying a solid, saturated, red, green or blue image. If you can't make one big enough for your entire screen, drag a smaller one around and look for a pixel that is not of the intended color.

While this thread is about dead pixels on an LCD, I had a dead
pixel near the middle of my CRT driven by a Matrox video card from 1996. When I replaced the card, there were no longer any dead pixels. So, the video card had a problem.

So a dead pixel saturates the whole image?

If you display an image of constructed only of blue, red or green values for each pixel, you can identify which of the three elements are missing/stuck for a pixel. A solid white image (full red, green and blue for each element) will reveal a completely unlit pixel. A solid black image can also help to reveal stuck pixels.

Joshua,

No, a dead pixel will not saturate the whole image!

An LCD screen is made up of a thousands of dots (pixels) and if one of those dots are dead (unlit) it will be black if your whole LCD screen is displaying a white image. If one of those dots is stuck on a colour (either Red, Green or Blue), you would notice it most if your whole LCD screen was diplaying a black image.

Under certain conditions these defective pixels are not visible... for example if you have a dead pixel and your LCD is displaying a dark image it would be hard to see, if at all. Also if you have one defective pixel which is permanently stuck on blue, it would be hard to see if you are shooting something which is blue as all the other pixels are blue too, and thus it would appear normal.

In my opinion, a dead (unlit) pixel is better than one that is stuck on a colour (lit permanetly on either Red, Gree or Blue Or White), because it is more noticable.

As with the other "Dead Pixel" post, each pixel is made up of three sub-pixels and it's the combination of the three sub-pixels that determine the colour, and if one of those sub-pixels are not displaying correctly you are faced with the above problem.

Cheers,
Jack

OK, that's what I thought.

Thanks for the input guys.