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Spot on! ... the second mask is to protect the blues which would turn green if not 'protected'...
Spot on again: If there were any other objects which were blue, they would be selected also. White fill would completely restrict that area from any modification, black would allow full modification. and therefore would have render the second mask absolutely useless....
A 25% gray allows some modification. The percentage gray should be varied on an image basis. Trial and error with the percentage until you get a blue that is satisfactory. ... Absolutely yes ... It becomes a bit a matter of personal taste, lacking more precise information about the hue and strenght of the original colour ...
Note: this means that any blue mungies in the blue areas will not be corrected.They will have to be cloned out. ... or minimized with "PS Dust& Scratches with the help of a Layer Mask" as I explained near the end ...
I followed the instructions below with no success until I Inverted the selection.... Can you believe that while I was writing this procedure all I had in mind was to not forget the Invert part.... which I forgot!!!! Thank you so much for letting me know!!! (I'm going to add it to my previous post so nobody else will have to find out the hard way!!!)
I became confused with the Apply dialog. Layer only had the option of Background not Merge. Of course I was violating the Golden PS Rule and was working on the background. As soon as I made a copy of the background and worked with that, the problem disappeared. I usually always write 'duplicate your background' first ... I really must be getting old ... ... but yes it is one of the golden rules of image manipulation ....
Anyway, I think the two of us make a great team for 'detailed explanations' ...
Wow - you guys blow me away! Flora - I wasn't expecting so much detail, but what you provided was truly useful. In fact so useful I immediately went and made a donation to RetouchPRO before attempting anything else. Thank-you!
Thanks to your input too leuallen, that was a great follow-up with your comments and personal experience.
I've since discovered that many of the slides do not suffer from the same problem, so your manual technique Flora will be put to good use and my automated request put to rest.
If all your images show a similar spotting, there may just be a semi-automated process you can use.
As many have said here, the Dust & Scratches filter is probably your best bet for eliminating the spots. Here's an approach that can be partially automated.
1) Duplicate your background layer (cmd/cntrl+j)
2) Apply Filter>Noise>Dust & Scratches.... Make your setting so that the blue spots virtually disappear. Don't be concerned at this point that the image is posterizing and losing all details. This will be corrected in the next steps. We used 15/13 for our setting.
3) Turn off visibility of this layer (click layer eye icon) and select the Background layer.
4) Go to Select>Color Range... and using the eyedropper from this dialog, click on the blue spots to make a selection of just these. TIP: Hold down the Shift key to add to your selection and hold down the Opt/Alt key to subtract from your selection.
The objective here is to make as good of a selection of the blue spots as possible. Use the Fuzziness slider to expand or contract the size of the selection. Also, don't be too concerned that other blues in the image are being selected (like the little boy's sweater). These will be replaced by the Dust & Scratches layer.
5) Once you have a good selection, click Okay, turn on the visibility of the Dust & Scratches layer and then click on the Mask icon at the bottom of the Layers palette. This will turn the selection into a mask which will use the Dust & Scratches layer as the fill for the blue spots.
Granted, it's not a perfect solution (you can still slightly see some of the spots) and a little postprocess-retouch will probably be required (we recommend the Clone Stamp Tool or the Patch Tool). However, you CAN make an Action out of most of this (including the Color Range... selection) which will get most of your images in the ball park quickly. The key is to make as good of a selection as possible of the spots with the Color Range... selection feature.
Hope this helps.
Just a quick aside on the source of the defects. Back around 1970, I was stationed in SE Asia where I took mostly 35mm color transparencies. Most were Kodachrome which had to be sent to the Kodak lab in Palo Alto for processing, but a few Ektachromes I had processed locally (Bangkok?, I don't recall). Several of these came back from processing with blue dots and streaks. I identified the problem then as bubbles that had prevented processing chemicals from removing the dyes in the emulsion. That doesn't help with retouching, but may shed some light on the source, which isn't caused by faulty storage conditions.
Hey Klaatu - sorry for the delayed reply, I've been away on holiday.
It was a great surprise to see an additional note to this thread and I really appreciate your detailed notes on a semi-automated solution. Certainly your result shows great promise and I look forward to trying it out. Thanks again!
mdavis - I read your note with interest. Now that I've had time to look at a few more boxes of slides, I see that many are not affected by the 'blue spot' disease. These slides were mostly taken in the 60's. However, the blue spots appeared some years AFTER, not at the time of development. I wonder if this is still related to your diagnosis?
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