Text and pictures © 2003-2014 Guillaume Dargaud
Last updated on 2014/08/26
"There is unexpected beauty hidden everywhere in this world — one just has to be open to seeing it. Remember that the next time you sneeze on your monitor." — Nathan Walton.
So you just bought a superb ultra-flat 25¾" LCD monitor, but it looks like there are a few 'spots' on it. Depending on how many and it'll mean return to the vendor or live with it. Or you could be about to buy one in a store and want to make sure there aren't any dead pixels. Just come to this page !
Testing for dead pixels is very simple, there's nothing to install. All you need to do is click on all the links below to load the various test pages and look carefully at the images for any sign of dead (black) pixel, lit (white) pixel or also colored pixel (here yellow and blue, even if it's difficult to tell the colors).
Now don't confuse a dead pixel with a fleck of dirt on the screen or a piece of dried snot. Wipe gently your screen with a dry clean rag before using the test procedure. How can you tell the difference ? Easy: move your head to the side of the screen: if the error moves to the next pixel, it's dried snot ! If you notice dead pixels, sometimes you can massage them back to life: just rub the screen by pressing a finger gently through a rag around the pixel. No guaranty but sometimes it works; LCD monitors are fairly fragile and easily scratched, so take it easy.
So even if you are lucky enough to not have any dead pixels on your monitor, you can still come back to this page when you are cleaning it in order to check that all the specks are gone. Some people pretend that you can also bring a pixel back to life by alternating its color very fast. I'm not convinced but you can always try to leave the 'cycle them' window open overnight... It may do the job if it doesn't kill your video card first or if your monitor doesn't go in sleep mode from sheer boredom.
|Click below. If the window that opens isn't full screen, press [F11]. When you are done looking closely, press [Ctrl][F4] or [Alt][F4] to close the window and proceed with the next one.||Click below, then press [F11] to view full screen followed by the [Backspace] key to come back to this page before you try the next one.||
If the two versions on the left fail, try the large images below and try and display them at 100% (no reduction, page fit or anything). This might work better on mobile devices which automatically change the size of whatever is displayed to fit the screen. Since the images are 2560x2560 you should see scroll bars (which you don't need to use). Low memory devices may choke on them...
As usual, press [F11] to go full screen.
|Cycle them||Cycle them|
Some advice about getting the best out of your screen:
"I'm a retard. I was trying to use Windows Magnifier to enlarge the dead pixel area to look at it better. I had it open for like 5 seconds, then like 'wait a minute'..." — RainmakeR.
LCD, plasma or OLED screens are not the only high-tech equipment to exhibit wrong pixels. A similar thing happens to digital cameras. A pixel of the CCD sensor that doesn't react to light is always black (dead pixel), while one with a short circuit always shows white (hot or stuck pixel), with the possibility that one of the 3 base colors only is dead or hot. Most recent cameras have special circuits that detect and remove such pixels from the final image, often as part of the noise reduction function applied during the creation of the image file. Note that a dead pixel may look very similar to a speck of dust on the sensor although a dead or hot pixel will stay in the exact same position between pictures while a speck of dust may move somewhat. A speck of dust will also often cover more than just one pixel.
How can you find if your digital camera has dead or hot pixels ? Well, it depends on the camera, but here is a general procedure for hot or stuck pixels:
The opposite procedure of taking an all-white image to see dead sensor pixels doesn't work as well because of light diffusion and bleeding between the pixels. A light grey defocused image would work better.
Right: Four dead pixels off a real digital camera CCD, the image is shown at 100% zoom, but because of the Edge effect, they show up bigger. I've grouped them to make them more visible; they all have similar shapes probably due to the demosaicing alogithm used.