I have an old photo from about 1900. It measures about 3.5X5 inches. The photo shows an old logging train. The image is just covered with blemishes and spots. The photos attached show the upper left quarter of the photo. I have been cleaning up the sky and the tree line.
Photo #1 is the original RGB scan.
Photo #2 is the scan after using curves to enhance the color.
Photo #3 is after cleaning the sky and most of the tree line but tree line is not finished.
Photo #4 Is a closeup of the tree line.
Photo #5 is the cleaned up image after converting to gray scale.

To clean the sky I started with a small healing tool. I used it to heal a larger and larger area. Then I used a big healing tool to go over the whole sky
In places like the left edge in #1 where the sky is very dark I cloned a clean area and dropped it on the dark area. Then I went over everything with a smudge tool and blended all the colors into a fairly even sky I did not make the sky a solid plain color and it appears as though there is some cloudiness. A nice quality I think. In cleaning up around the trees I zoomed way in and did my best to not eliminate the branches that are barely visible. When zoomed back out it looks like a pretty realistic picture

I hope you all will comment on my results and my methods. Cloning, healing and smudging are about as advanced as I am so far so I hope these methods are not seen as the "getto fix" This is a very slow process but I am very impressed with my progress.

Heres the last 2 pics...

You have done a great job of the clean up. Personally, I would have used an S-curve on the curve tool to get some nice contrast again and left it as it was (dirt and all). I think it is a rather charming feature of an old photograph to show a bit of age. Just my opinion though. There are special programs that introduce grunge to make a photo look old.
Nevertheless, your clean up is well done

Good job!

Looks real good, but i too would want that old picture to look it's age.A few scratches and dents if you know what i mean.

I only see two photos ...