How do I remove dead pixels from a digital photo?

Question

I have a Nikon D90 and until recently it has been working just perfectly. While viewing a set of photos I had taken I'm starting to find these little nasty dead pixels:

They only show up when zoomed in - however now that I know they are there I can pick them out of just about any photo I shoot. What are some techniques to go about removing these?

Asked by Geoff Dalgas

Answer

Adobe Lightroom (I know, broken record) has a tool to spot clean. Once you define the area, you can apply it to all photos in a collection.

As Mister Shaw has commented on, some camera's have dust delete capabilities, which may work.

Also, have you considered (out-of) warranty repair on your body?

Answered by Alan

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Why do I have a red dot in every photo?

Question

Every picture that I took today have a red dot on the same place in every photo. It looks like a monitor "pixel error". Is just the lens dirty or did something bad happen to my cam?

Here some samples. Best mode to detect the dot is download the picture in original size (click the (i) then download)

Answer

You're exactly right — it's the same thing as a monitor pixel error, but on your camera's sensor rather than on an LCD screen.

You can either fix it in post-processing (automatically, with many RAW-processing packages) or have it mapped out with the camera's firmware.

If you're lucky, your camera model includes a built-in feature to do that yourself in the field; failing that, it's almost always covered under warranty service.

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Are there bad effects of frequent pixel-mapping?

Question

I read on two different sites that pixel mapping should be done once or twice a year. But sometimes I end up doing it once a month. Will it have adverse effect on the CMOS image sensor?

Answer

I can't imagine why. The actual operation is non-destructive — it just reads from the sensor when it should be dark (possibly multiple times), and records what is stuck on. Then that's put in a table — a map — which is used to mask out those pixels later.

Updating that map can't really be destructive either. I mean, it's probably stored on flash which can only have 100,000 writes or so, but that'd only be a problem if you were doing it every second, not every month.

I think the advice for once or twice a year is because new defective pixels can crop up, but it's unusual, and shouldn't happen frequently. Running yearly or half-yearly should catch them on average. Of course, if you notice one before then, running the mapping right away is clearly the thing to do.

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Why don't we get hot pixels when using live view?

Question

Why don't we get hot pixels while using live view mode, but do get then on a long exposure? I read somewhere that they appear due to the sensor being activated for too much time, but then, live view should also show them.

Answer

On a long exposure charge is allowed to accumulate on the sensor over a period of time, whereas in live view the sensor is discharged for every frame (so thirty times a second or so). Some hot pixels result from slow charge leakage which only occurs during a long exposure, hence you wouldn't expect to see these in live view.

Also liveview subsamples the sensor so you dont see every pixel.

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