How to remove stain in scan of old slide.

[Doug Earle]

I have several old slides of some family that have deteriorated in storage and appear stained with Magenta "squiggles". I've tried removing them by using the healing brush in PS and LR with little to no success.  I'm wondering if there's another approach that would eliminate them?   (The original slides were severely underexposed and improperly stored over the years, so I had them professionally scanned.  The photos are interesting only to family who had visited the locations, in case anyone is wondering why I'm attempting to do this.   My goal is to simply get a snapshot quality photo that would be printable. Nothing professional in other words.).

I've attached one of the photos to give you an idea of what I'm working with.

[davescm]

Try a curve adjustment on low values in the green channel

Dave

[Doug Earle]

Thanks, I'll give that a try.  I have a very basic skill level with PS and never would have tried that on my own.  Can you give me a simple explanation of what led you to try that, since the squiggles were a dark magenta?  (I'm trying to learn).

[davescm · Accepted solution]

I looked at each channel in turn to see where the marks showed the worst. They showed particularly strongly in the green channel as dark marks. So, by brightening just the darkest greens slightly but leaving the rest untouched, the visibility of the marks was reduced. It will mean some detail loss in the darkest greens but that does seem less obtrusive than the original marks.

Dave 

[Trevor.Dennis · Accepted solution]

I did wonder about Point Color seeing as it is the most up to date tool for small area colour correction, but I tried it and it did not have the range for these highly saturated artefacts.   Colin Smith has a good video on Point Colour, so check it out if only to add it to your Photoshop toolbox.

I also tried the old school method targeting the colour range with a Hue/Saturation layer, and that worked better, but I had to expand the color bars moving the inner sliders further out towards the primary sliders (as below)

That got things under control enough to clean up with the Remove tool, but that doesn't work on the Adjustment layer of course, so it was a Copy Merged layer (Shift Ctrl Alt E) to add that layer with the Hue/Sat fix, and the Remove tool to gently tap out the lightly bright areas left by the Hue/Sat layer.

[davescm]

I believe the artifacts in question are the dark squiggles on the background (look at the green channel). I think those brighter points were fireflies or similar and therefore a wanted part of the image.

Dave

[Trevor.Dennis]

Ah hah!  Thank goodness for technology. 😞

[davescm]

We've all done it. At first I thought the same. 🙂

Dave

[r-bin]

Option based on Content-Aware Fill in Lighten mode. The main thing is to select the spots correctly. It's hard to explain how I did it, but you can take the idea of Content-Aware Fill into account.