I've been asked to scan a 120 color neg that has damage to the surface of the emulsion. ICE has fixed some of the minor problems but I'm stuck with manually fixing the damage from what looks like a finger print and something that appears to be a fungus.
When I look at the color channels in Photoshop, CS 5, the majority of the damage is in the Blue channel the Red and the Green show only minor problems.
I could use only the Red channel and make it a B/W print but am looking for a method of use the the Red and Green channel information to rebuild the blue. Is this possible?
Thanks in advance.
You might expiment with conveting to Lab color and experimenting with that method. Then change back to RGB.
Back in the old days scratched negatives could be coated with a light oil and put in the enlarger. That seemed to help, but kind of scarry putting oil on negative.
Scanning using a professional scanning fluid like Kami along with a clear overlay material like DuPont C-42 will go a long way to minimize surface problems in a scanned neg. You either need a special film holder or a drum scanner to to that though, and it's a messy pain to work with if you've never done it before.
You may be able to help your cause out using the Channel Mixer. Use it as an Adjustment Layer and blend a percentage of the good channels into the bad one(s). There's a good chance that will cause a color shift, but that can usually be dealt with by other means.
Take a copy of the file and convert it to Lab color. Look at the "a" and "b" channels. If some of the damage resides in either of those channels, you can often apply a liberal dose of Gaussian Blur - something like five to seven pixels to either or both channels and fix your problem without any undue effect on the overall image. I usually would do that to a duped background layer and be prepared to mask off any super saturated areas that smeared from the blur. If, in fact, the Lab trick helps, then flatten your image and paste it back on top of your original. You can then toggle it on and off to see the improvement.
You may never avoid all manual labor on this, but you might avoid some.