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Related to “Spots” in my pictures. :-(, I've discovered these lovely purple spots in all of my recent (1500ish) shots, but they're much different than his smudges.

I'm shooting with a Nikon D5000 + Sigma 10-20mm. Here's a crop from a random shot (edited in LR to make the dots more distinguishable):

purple spots

What does it mean and what can I do about it?

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Related question:… –  chills42 Feb 17 '11 at 15:45

4 Answers 4

up vote 13 down vote accepted

These are probably the result of defective pixels on the image sensor, and are commonly referred to as "stuck", "dead", or "hot" pixels.

This is a common occurrence with image sensors. There are several ways to deal with this problem:

  • Replace the camera - this is probably the most expensive solution
  • Replace the sensor - this may be as or more expensive than replacing the camera
  • Sensor pixel mapping - this is often an option that can be used to avoid changing the hardware. If you send your camera in for support, the technicians can tell the software to ignore the dead pixels.
  • Software mapping - there are different software tools that can be used to ignore dead pixels, but usually these work best if shooting RAW.
  • fixing them by hand - this is time consuming, but you can just hand edit your images
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Also, slightly unrelated, but there is a "Service advisory" for the D5000:… so you might be able to have this repaired at low/no cost –  chills42 Feb 17 '11 at 16:00
Some camera bodies have hot-pixel mapping available as a user-accessible menu option. This is by far the best solution, but unfortunately many camera makers use this as a price differentiator, reserving the feature for higher-end bodies. Something to keep in mind next time you're shopping for a camera body. –  mattdm Feb 17 '11 at 17:58

They look like stuck pixels, basically these sensor elements always output a high signal regardless of the incoming light. This is being incorrectly interpreted by the demosaicing algorithm resulting in purple spots.

As a sensor defect there is no "fix" as such but you can map stuck pixels in software which prevents them from contributing to the final picture.

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Are they always the same color?

Are they always in the exact same location?

Have you tried different lenses?

Have you had the sensor cleaned?

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Good questions! Yes. Yes. No. No. I tried #3 with different lenses but I was unable to find anything. I then went back to my old lens and I couldn't reproduce the problem. I need to set aside some time for experimenting. –  glenneroo Feb 22 '11 at 13:46
Update: Yes. Yes. Yes. Yes. –  glenneroo May 28 '11 at 14:57

I agree with the assessment that they are stuck pixels. My S90 recently developed a few stuck pixels, and while I want to send it in for repair, I have worked around it in the interim with an Aperture adjustment preset.

I imported a photo exhibiting the problem, then used the retouch tool to repair the image. I then selected Presets -> Save As Preset and titled it “Fix S90 Stuck Pixels.”

When I import from that camera, I select that preset, and all my images are repaired automatically.

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