bad pixel

(redirected from Hot pixel)

bad pixel

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.

Polarizer Damage
This red pixel is due to damage on the polarizer, which is the screen layer in front of the user (see LCD).

It Can Be Annoying
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 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, it is placed over the stuck pixel and left alone for an hour or more.
References in periodicals archive ?
Justin Maki, leader of the team that built and operates Curiosity's navigation camera, said that in the thousands of images that they have received from Curiosity, they have seen ones with bright spots nearly every week and it was the hot pixel that has been around since they started using the Right Navcam, the Huffington Post reported.
The software can perform edge enhancement, image mirroring and image binning in the vertical and horizontal directions, as well as hot pixel correction.
When considering such critical performance parameters such as sensitivity, cross-talk, hot pixel count, and manufacturability, Aptina's MT9F001 technology is the right solution for high performance digital consumer camera products.
After close examination of my Astrovid StellaCam3 image, I'm almost certain the mystery object is a hot pixel.
The low noise in the Trius-SX814C and the camera's regulated, two-stage TEC cooling means that what few hot pixels are produced in most exposures can be removed using pixel-rejection algorithms when stacking sub exposures.
This produces a strong signal-to-noise ratio, while rejecting outlier pixel values such as satellite trails, hot pixels, and other random signal that doesn't repeat in every exposure.
Images with its low-noise Sony chip only resulted in a smattering of hot pixels that disappeared when dark frames were applied.
The best way to get rid of hot pixels is to subtract a dark frame, a picture taken with no light reaching the sensor, but in all other respects just like the original, with the same exposure time, ISO setting, and sensor temperature.
The dark frame will record primarily the CCD's dark current, and subtracting it from your light exposure will greatly reduce so-called hot pixels in your image.