For this past Father's day, I worked with my brothers to create a slideshow of our awesome dad. My older brother scanned old photos from slides and photos, I did some of the photo restoration and my younger brother put the photos together and made a fun slideshow.
For this tutorial, I will show you how I did some of the restoration techniques; specifically, I will talk about how to remove Moiré other patterns on the photo. (A Moiré pattern is the dot pattern you see on many old photos. Click here to read the Wikipedia article on Moiré patterns)
The first thing we will do to the photo is to remove the white dots all over the photo. You may observe when working with old photos that often there will be a pattern. Sometimes the pattern is related to the paper material, or how the photo was printed. In the photo you see below, you will notice that there are white repeating dots all over the photo. This is due to the paper texture reflecting light when it was scanned.
Whenever I work on a photo, I like to duplicate the background layer. This allows me to always go back to the original photo so I don't loose data. It is also useful to use the original layer to compare to the current working layer.
Removing dots or patterns can be done a few different ways. The most effective way would be to use the healing or clone tool. The main problem with this is that it would take hours and hours to do. It is simply not usually worth the time spent doing this. Probably our next best solution would be to do a blur. I did a Gaussian blur and increased the blur until I could no longer see the white dots.
The problem with doing this is that now we have a blurry image. We can help remedy this by applying a sharpening filter to the image. I chose smart redux for sharpening (this is only available if you have the redux/resynthesizer plugin already installed).
Even after sharpening the photo though, it is still a little blurrier than I would like it. This is where I use the original layer. If you change the layer mode to Multiply, it will multiply your blurry (pattern free) layer with your original non blurry (but has white dots) layer. Multiplying these two layers adds a bit of crispness to the photo.
Multiplying the layers makes the photo a bit darker than I would prefer, so I no will use Colors>Levels and adjust the levels until I am satisfied.
At this point I will just apply basic photo restoration techniques such as using the clone and healing brush tool. These tools are useful for removing dust and specks such as what you would commonly see with scanned photos.
Now that I have flattened the image, I am going to sharpen the layer once again.
Look below to see the original scanned photo.
Here is the restored photo after making the edits in the Gimp.
To better show the white dot pattern that was showing up, look below at the zoomed in photo.
Below is the photo after I have applied the Gaussian blur and multiplied the layers.