Faulty Pixels In Images - Nokia N900 Service Manual

RX-51
Camera Module Troubleshooting
Figure 44 Image of point light sources taken with a clean protective window
Figure 45 Image of point light sources taken with a dirty (finger print) protective window

Faulty pixels in images

Faulty pixels are pixels that do not respond to light in the same way as the pixels around them. There are
three main types of faulty pixels, dead, stuck and hot pixels.
Dead pixels are always black or significantly darker than their surrounding. Dead pixels appear as black spots
in all lightning conditions. Camera modules producing images with dead pixels that are clearly noticeable
should be replaced.
If the pixel remains always saturated to its maximum value it is stuck. Stuck pixels may appear as red, green,
blue or white spots in all lightning conditions. Camera modules producing images with one or more stuck
pixels should be replaced.
Hot pixels are pixels that easily saturate in dim light conditions. It is normal to get a lot of noise and hot
pixels in night conditions or otherwise dark conditions. The hot pixels should disappear when the ambient
light is increased, but may still appear in darker areas of an otherwise well illuminated scene.
When examining an image for defect pixels, test images should be viewed as 100% enlargements on a PC
monitor.
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