Warm/dead pixels are imperfections in the CMOS/CCD device of your camera. They are usually a different color from the surrounding pixels in a photo, mostly visible in dark parts of the photo.

A good way to test your camera for warm/dead pixels is to take a photo with the lens cap on. Or, if you own a camera that doesn't have a lens cap or the lens cap will interfere with the lens then go into a closet or bathroom with the lights off (complete darkness) and take a photo. The longest exposure you can get your camera to go (manual mode might provide longer shutter speeds) will show you more warm/dead pixels.

Then you can use this application to analyze the image for a detailed report.

Another info source, from climbers , is here: »webpages.charter.net/bbi ··· ls.html#