A defective pixel on an LCD screen. Bad pixels are often transistors that are permanently dead and appear as black dots or permanently energized and show up as white or colored dots ("hot pixels"). These pixel defects usually occur at the time of manufacture. However, if a bad pixel appears after the screen has been in use for some time, it may also be due to a dented or scratched polarizer (see LCD
Sometimes, it is possible to repair a bad pixel by gently rubbing the screen with a cloth or running a pixel repair over the area for several hours, the latter repetitively flashing colors on and off to attempt to dislodge a stuck pixel.
Does It Matter?
It depends. On an LCD TV, which is displaying motion and is situated several feet from the viewer, dead or lit pixels may not matter. On a computer monitor only two feet away, they may be very annoying, especially if located in the center of the screen. Equipment manufacturers have different policies regarding defective pixels. They typically state that if a certain number of bad pixels exist when the display was purchased, the unit may be returned.
It Can Be Annoying
This red pixel is due to damage on the polarizer, which is the screen layer in front of the user (see LCD
One bad pixel can be very glaring, depending on where it shows up; witness the single, green pixel on this man's black coat.
Test for Yourself
Dead pixel testers such as Dead Pixel Locator from Astris.com let the user find bad spots by displaying different colors across the entire screen.
Repair Stuck Pixels
Pixel repair programs cycle rapidly through all the colors to possibly dislodge a stuck pixel. There is no guarantee, but if a stuck pixel is annoying, it is worth a try. When this animated GIF is retrieved from Killdeadpixel.com, it is placed over the stuck pixel and left alone for an hour or more.