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Adobe Lightroom 5 came out with a new feature called "Visualize Spots" that helps you to find dust. More information on the feature can be found here: Adobe Help

How can I achieve a similar function in Adobe Photoshop to find dust spots or similar imperfections? I sometimes am working on an image in Photoshop for more serious editing and don't want to import it into Lightroom just to perform this. I also prefer some of the healing tools in Photoshop over Lightroom so it might be more useful in those cases.

Here is an example image with quite a few spots in it: https://dl.dropboxusercontent.com/u/95761/church_dust.tif

Example image: enter image description here

For reference, here is what Lightroom 5 was able to find in the example image: enter image description here

Attempt based on answers

Based on the two answers thus far, I tried two tests.

Original on the left, Matt Grum's in the middle, and Unapiedra's first solution on the right: enter image description here

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@mattdm, maybe it shouldn't be labeled results but his edit shows that the answers so far aren't working... –  Unapiedra Jul 23 '13 at 9:06
    
@dpollit: What does the second image show? Could you add some descriptive text? –  Unapiedra Jul 23 '13 at 9:11
    
@dpollitt From the text you wrote ("Results" and "which is a bit different but nonetheless the techniques helped"), it looks like a summary-of-all-answers rather than "I tried some things and they aren't working". If you meant the latter maybe that could be explained better? If you did mean the former, that's better as a new answer. –  mattdm Jul 23 '13 at 12:12
    
@dpollit: Could you provide the two crops you used for testing as 16-bit TIFF (or similar), please? @ Everyone: If you have Lightroom 5, what does the result look like when done on the example images? Would be great to have some "best solution" comparison. –  Unapiedra Jul 23 '13 at 12:20
    
@Unapiedra - I have added a TIF example, and a LR5 comparison. Thank you for all of your help. –  dpollitt Jul 23 '13 at 17:11

4 Answers 4

One thing that was done before Lightroom 5 came out, was to create a strong z-shape in the curves.

Here is an example with Darktable. Note the huge dust spot in the sky (to the right of the centre tree). Showing dust spots with curves.

Here is Scott Kelby doing it in Lightroom 4. The technique should be doable in Photoshop just the same.

Update using dpollit's test image

I used dpollit's image that he used to compare the two answers given so far. I grabbed this image from here, so the quality has deteriorated further.

There are three things I would like to note:

  • It's not working that great in either case.
  • I am not sure dpollit has edited the L-curve like I did because the results he got are quite different in colour from my results. Yet, I am not sure which curve to use best.
  • You can make out a third spot in the middle and slightly to the right of the two marked spots.

Result on left, original on the right.

resultoriginal

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Based on the image provided in the documentation:

Copyright © 2013 Adobe Systems Incorporated. All rights reserved.

it looks like you could get a similar effect using the "find edges" filter in Photoshop, converting to greyscale and then inverting. You'll want to duplicate the background layer first, so you can flick the effect on and off.

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A way I find good for quite a lot of images is as follows:

  1. Create a copy layer of your image
  2. Select the layer
  3. Click Adjustments > Equalize
  4. Select the original background layer with the equalized layer in front and visible
  5. Use the healing tool to fix the spots
  6. Bin the equalized layer
  7. Done
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Using dpollit's source image with dust spots, I tried to use the method as suggested in my other answer, and it didn't help at all.

So here is a new technique: Enhance local detail and denoise.

Result

You can see all the settings I made.

  1. In local contrast, push detail slider to the very right.
  2. Denoise (default settings, just enabled) gets rid of a lot of the noise in the sky but not of the dust spots.

combining tone curve and local detail

In dpollit's image the tone curve made absolutely no difference.

In my earlier test image, however I found that using both increased local detail and the tone curve did improve. Without the tone curve I didn't see as many sensor spots. ( I really need to clean my sensor or not shoot at f/22.)

Here is the result: Better

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