Fixing discoloration (from sensor overheating?)

I need some suggestions about how to isolate and fix some discoloration in the following image. I believe it is due to my sensor overheating while shooting a long exposure, though I’m open to suggestions about what it may be. I had shot 20-30 long exposures between 30 sec and two minutes when this happened.

So far I’ve tried the following:

  • select the area around it and play with hue/saturation. This worked ok, but it left some light patches
  • wavelet decompose into 5 channels.
  • Couldn’t see anything noticeable in any channel. examine each of the RGB channels. Couldn’t see anything noticeable, similar to wavelet decompose.

Any suggestions about the cause and potential fixes would be much appreciated! I otherwise like this photo very much!

Could be heat, could be stray light coming in via the viewfinder from behind. Is it in the same spot in other shots? Are we looking at the whole image? If that’s the whole image, delete it and move on. If it’s a crop and the whole image is worth spending time on, then fire up GIMP, sample the color from a clean patch of floor as the one I circled, and paint over the blob in “Chroma (LCH)” mode:


10 seconds, fixed.
Yes you could spend half an hour doing it better by going to Lab mode and filtering out only very low frequency details to get a layer you could use to invert the damage, but that’s not a good time investment.

If it’s a regular problem for you and occurs in the same place, take another shot using the same parameters but with the lens cap on and use that other shot as a dark frame.

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I’d initially agree with @Morgan_Hardwood. Sensor overheating usually presents differently, doesn’t it? Hot groups of pixels? This looks more like a light leak/streak from somewhere…

I had only thought about the sensor because I had been shooting long exposures all day, though none of the other images from this shoot exhibit this kind of discoloration. I had shot basically the same frame with my 40mm lens too, and there is more fogging, but it neutral in color.

Anyway, after find the gimp dev PPA, I got 2.9 and applied the chrome fix as @Morgan_Hardwood suggested. Worked like a champ.

Here is the image:

Many thanks for the help; looking forward to gimp 2.10. Hopefully it will make it into the Debian Jessie backports ;D

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Hopefully it will make it to planet Earth first :wink:

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