This tutorial explains one technique used by image editors to fix dirty images. It also works great for minor scratches, scrapes and blotches.
A lot of photographs that are taken from behind glass usually come out noisy and with dull blotches on them. Fortunately photoshop provides a very easy way to fix these photographs.
Open the image you want to fix in photoshop. In the layers panel right click on the layer containing your image and choose Duplicate Layer. Name the new layer 'layer overlay'.
Now go to filter blur Gaussian Blur and increase the blur settings till the noise,and dust is no longer visible and press O.K.
Click on the Layer in the Layers Panel and from Blending Modes (the dropdown menu at the top of the Layers Panel) choose 'Hard Light'. The Blending Mode that works for you will vary from image to image. So you will need to experiment
As you can see the result is a big improvement from what we started off with. Once again a reminder that this is just one technique in photoshop's massive aresanal of photoshop tools.
