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Using the Curve tool to visualise dust spots

Lars Broberg
In one of the latest webinars David showed an interesting way to visualise sensor dust using the Curve tool.
He used a preset in Curves which made it very easy to find dust spots.

I tried to do the same, using the spot tool to remove the spots.
But when I reset the curve tool, either using another preset, or by reset the changes I've made, the spots reappears.
Shouldn't the spot tool work "by itself", so when I make an adjustment in Curves the spots I have removed stays removed?

There may be a step I have missed, some trick to make this work...
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Comments

5 comments

Date Votes
  • HansB
    Out of curiosity: could you point me to the webinar and play time?


    Regards,
    Hans
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  • Lars Broberg
    Sure Hans

    Here is the webinar, and the time where David talks about the "trick"

    https://youtu.be/okVI9fArHe8?t=59m18s
    From 59:18 to 1:01:25
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  • HansB
    I'm a bit confused by 'dust' and 'spot' in your post. The 'Spot Removal' tool offers both.

    I've tried the following:
    + change luma curve (like in the video)
    + add a dust removal (sensor dust)
    + add a spot removal (flying bird)
    + reset luma curve
    The dust is still removed, the spot too. No tricks applied.

    Btw, I would either use a individual curve per image or combine the preset with individual, harsh clipped upper and lower levels in the level tool to get the dust (not spot) brightness to a level where the curve creates high contrast. At the turning points of the up-down-up curve, the dust 'magically' vanishes.


    Regards,
    Hans
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  • Lars Broberg
    Thank you very much for your help HansB, I appreciate it!

    I found the "error", why it didn't work for me.
    I was using presets for the Curve tool.

    I chose the "5-point-AllChannels" as in the video.
    Changed the curve, again as in the video.
    Removed spots, spot tool, type "spot" and not "dust".
    When I reset the Curve tool, the spots I had removed came back.

    But if I instead don't use the presets, just manually change the luma curve.
    Remove the spots, and then reset the Curve tool - IT WORKS!!

    Again, thanks a lot for helping out HansB
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  • HansB
    Funny. I can use the '5-point-AllChannels' and modify it. And I can use the up-down-up curve saved as user-preset.
    In both cases, removed spots remain removed.

    I wonder what the difference is that makes it work. I'm working on Canon cr2 raw files, no adjustment layers.


    Regards,
    Hans
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