I recently restored a photo using a technique from Katrin Eismann's "Restoration & Retouch" book successfully. I would like to share it with you.
As always, our beloved distributors have the greatest talent of hiding the most difficult damages in the thumbnails when we pick the photos to restore.
I just finished a difficult one and was looking for an easy one to catch my breath. This one looked innocent enough. I thought I only had to do a little level and color adjustments then clean up the minor damages around the boarder. It would be ready to go home.
The original

When I opened the hi-res download, to my horror, there were numerous orange spots on her hair and other places. The original was a 12x18, so the area I shown below actually presents an area of about 4"x5.3". At that size, there was no way to hide the damages.
An selected area showing the orange spots

I checked the RGB channels. Lo and behold, the blue channel contained all these dark spots corresponding the the orange spot damages. Fortunately, they only existed in the blue channel.
The selected area in blue channel

My first instinct was to repair the spots in the blue channel.
It proved to be difficult and tedious to remove the spots and still retain the texture of her hair. After an hour of work, I managed to clean an area no more than two square inches. I knew I needed to look into some other methods. I vaguely remembered Katrin's book had a section about restoring a photo with the blue channel completely faded. She replaced the blue channel with the Lightness channel in Lab mode.
I checked the Lightness channel and luckily, it not only had much much fewer spots, it had approximately the same appearance as the blue channel.
The selected area in Lightness channel of Lab mode

The steps of replacing the blue channel with the lightness channel:
1. Open the original image file
2. Select Image>Mode>Lab color
3. Select the Channels tab and click on the Lightness channel to activate it
4. Select Select>All then Edit>Copy
5. Select the History tab and click on the Open before the Lab Color entry to discard the Lab Color mode and return to RGB color mode
6. Select the Channels tab and click on the Blue channel to activate it
7. Select Edit>Paste to replace the blue channel with the Lightness channel
The selected area with the blue channel replaced by the lightness channel

As you see in the image above, the orange spots were gone and the hair looked much better. But the side effect of replacing the blue channel with lightness channel was that the true blue areas now appeared green as below:
The original with the blue channel replaced by the lightness channel

These side effects may be corrected by selecting the areas that should be blue and do color balance by pulling the Yellow-Blue slider to the Blue.
Color adjust the blue jeans after blue channel replacement

The complete restoration
