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Author Topic: Removing Sensor Dust From Multiple Images  (Read 2868 times)

Peter McLennan

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Removing Sensor Dust From Multiple Images
« on: April 23, 2011, 09:09:37 pm »

I have discovered that I have a very dirty imager chip on on my D300.  A result, no doubt, from my recent adventures in the Mojave Desert.

The dust remains on the sensor.  I haven't cleaned it yet.   Can I use some kind of blank image of the dust ONLY to subtract the sensor dust errors from many images?

I was thinking that, if I shot a white card at F22, I could image just the dust and somehow use this image to subtract the dust from my pictures.

Anyone done this successfully?  Any strategies to share?

I do understand that you can manually heal a single image in ACR and then allow ACR to process other images from that repair data.  I'm trying to avoid doing this manually, since I can't seem to do a good enough job with the healing tool in ACR.  Clear, featureless skies are hard to heal.

Thanks for any suggestions.

Peter

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digitaldog

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Re: Removing Sensor Dust From Multiple Images
« Reply #1 on: April 23, 2011, 09:26:25 pm »

I do understand that you can manually heal a single image in ACR and then allow ACR to process other images from that repair data. 

Yup, if the spot is pretty much in the same place in multiple images, it works quite well. And because this is a non destructive, metadata edit, even if you get 90 out of 100 just right, its super easy to fix the other 10 by moving the healing brush area. So its not manual for all the images. Its quite possible you can fix a large number with a simple copy and paste of the single brush stroke.
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Peter McLennan

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Re: Removing Sensor Dust From Multiple Images
« Reply #2 on: April 24, 2011, 11:20:03 am »

Thanks, Andrew.  I attempted a few manual cleanups with the healing tool in ACR and copied those results to the other images via "synchronize" with multiple images open in ACR.  It worked better than I expected.  Thanks!

Peter
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monoprint

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Re: Removing Sensor Dust From Multiple Images
« Reply #3 on: April 27, 2011, 09:48:31 pm »

I've used Adobe Camera Raw to remove a dead pixel from a series of ~500 time-lapse images of the sky. Load all the images, correct one and tell acr to apply the same correction to all.

Bill
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plugsnpixels

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Re: Removing Sensor Dust From Multiple Images
« Reply #4 on: May 04, 2011, 04:37:14 pm »

SensorKleen is another software option.
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DerW

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Re: Removing Sensor Dust From Multiple Images
« Reply #5 on: May 10, 2011, 06:13:33 pm »

In fact you can remove sensor dust from your images if you photograph a white paper with the same settings, but instead of using a subtraction, you'll have to use a division to get rid of the dust (which works darkening like a multiplication).

A tutorial for this can be found here: http://photoshopnews.com/2010/04/13/removing-sensor-marks-in-photoshop-cs5/
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Peter McLennan

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Re: Removing Sensor Dust From Multiple Images
« Reply #6 on: May 28, 2011, 01:02:25 am »

DerW, Thank you!  I can see that this technique has some extraordinary advantages.   Unfortunately, my "reference" image of the dust wasn't shot the way Martin Evening (wisely) suggests.  I used a very small aperture to shoot the reference image and so it didn't match what was in the original.  I had to resort to blurring the reference image to make the technique effective, but it certainly does work.  My dust-laden image was of a relatively featureless sky - always difficult to clone successfully - yet this "divide blending" worked quickly and well.

FWIW, my dirt-laden sensor took five Sensor Wipes to clean effectively. : (  A result of three weeks shooting in the Mojave Desert.
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