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long exposure cleanup
  
 
MikeW
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p.1 #1 · long exposure cleanup


What do you guys use to clean up hot pixels in your long exposures?

I thought my D4 was bad but took a few with the D800 yesterday & I have thousands of white dots & hundreds of coloured ones. I can't clone all them out obviously, they are only visible really if you zoom in a little, but I can't see a print being possible.

Thanks for the help,


Mike



Nov 09, 2013 at 04:18 PM
Alan321
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p.1 #2 · long exposure cleanup


I guess that you're supposed to use the built-in dark frame subtraction (long exposure noise reduction). Try taking a new long exposure at similar camera temperature with the lens cap on and a small aperture. Use the same ISO and exposure duration.

Then there'll be a way to subtract the bright dots in that one from those in your other shots. Should be easy if you know how to use Ps (which I still don't).

Have you applied any noise reduction in something like Ps or Lr ?

Out of interest, were you combining the long exposure duration with high ISO or sticking with the lower ISO ?

- Alan



Nov 09, 2013 at 05:37 PM
MikeW
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p.1 #3 · long exposure cleanup


Just a 160second exposure during daylight with the big stopper at base 100 iso. I've tried using Long exposure noise reduction before but it doesn't do it. I have used Niks Define & painted the sky & water, it gets rid of most of them, but the image degradation is bad imo.

I was hoping someone had some of their methods to share in combating hot pixels in landscapes. I have posted about hot pixels before, my shock at having them, but now accept they are there & want to deal with them



Nov 09, 2013 at 06:27 PM
Alan321
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p.1 #4 · long exposure cleanup


I still think that dark frame subtraction is your best bet after the event. Use it with layers in Ps and you should have control over how much you subtract from the main image.

At capture time, you might get better results in some situations with multiple shorter exposures onto a single frame at suitable intervals to reduce the heating of the sensor electronics and hence the hot pixels. It will also average out other noise. The D800 will do this but it's no good for star trails and moving subjects.

Do what you can to keep the camera shaded and cool.

Use a bigger aperture and try focus stacking shorter exposures instead of using a small aperture.

Use a shorter exposure and underexpose, and fix the exposure in processing. Perhaps the hot pixels will not get so hot.

- Alan




Nov 09, 2013 at 08:26 PM
Bifurcator
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p.1 #5 · long exposure cleanup


Gimp tutorial part 1
Jim Solomon's Cookbook - Processing
Creating FFT frames for post processing long exposures

And so on… Good luck.



Nov 10, 2013 at 05:34 AM
Mr Joe
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p.1 #6 · long exposure cleanup


What was the ambient temperature when you took the exposure? For anything over about 65 degrees, using the in-camera long exposure noise reduction (LENR) is usually a good idea.


Nov 10, 2013 at 05:07 PM
 

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Eyeball
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p.1 #7 · long exposure cleanup


You might want to contact/follow this guy. He was experimenting with software to fix these hot pixels on D800 raw files but I couldn't find where he's actually made something available.

http://www.flickr.com/photos/davideanastasia/8359200132/

I suspect that what is aggravating the problem is that hot pixel removal calculations in-camera (with the long exposure noise reduction) and with software like Lightroom/ACR is that they are geared to bright pixels on nearly-black backgrounds. Your images, since they are taken with ND filters during daylight with non-black backgrounds, confuse those algorithms and don't allow them to work effectively.

If you have a recent version of Photoshop, I would suggest making your own hot-pixel mask from a long-exposure with the lens cap on and then use that mask on your images with a content-aware fill. That should fix the spots with virtually no impact to the detail in the rest of the shot. Using the dust and scratches filter could also work but you might want to selectively paint a D&S layer onto a good layer to reduce the impact to non-spotted areas.




Nov 10, 2013 at 05:48 PM
hugowolf
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p.1 #8 · long exposure cleanup


Taking a shot with the lens cap on, at the same ISO, same shutter speed, and at around about the same ambient temperature, then adding it as a layer in Ps with the blending mode set to subtraction, should work. If it doesn’t, then it probably isn’t hot pixels causing the problem.

Brian A



Nov 11, 2013 at 06:08 AM
parsons
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p.1 #9 · long exposure cleanup


this is, and or was a major known issue with the d800, and no amount of dark frame subtraction will resolve the issue. this is why I never got around to buying the camera for my landscape work.

a good read, and your problem I expect is further down the article, and the way in which to partially resolve this is in your raw software program, mainly though unless corrected recently using other options, your best bet is by using raw therapee:
http://scottreither.com/blogwp/2012/07/01/nikon-d800-e-long-exposure-issues-problems-2/



Nov 11, 2013 at 11:43 AM
hugowolf
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p.1 #10 · long exposure cleanup


parsons wrote:
this is, and or was a major known issue with the d800, and no amount of dark frame subtraction will resolve the issue. this is why I never got around to buying the camera for my landscape work.

a good read, and your problem I expect is further down the article, and the way in which to partially resolve this is in your raw software program, mainly though unless corrected recently using other options, your best bet is by using raw therapee:
http://scottreither.com/blogwp/2012/07/01/nikon-d800-e-long-exposure-issues-problems-2/


Yet the article recommends using dark frame subtraction?

Brian A



Nov 11, 2013 at 03:49 PM
parsons
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p.1 #11 · long exposure cleanup


hugowolf wrote:
Yet the article recommends using dark frame subtraction?

Brian A


yes, but it does not solve it.



Nov 11, 2013 at 04:34 PM





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