How do I make Photoshop's “Dust & Scratches” filter only apply to areas with problems, rather than blurring the whole image?

Question

When removing dust and scratches or when I want to apply a filter at a certain place in the image, Photoshop blurs all the image (Filter -> Noise -> Dust & Scratches). Why is that?

I just need Photoshop to blur the image at the indicated spot where the unwanted dust or scratch is located.

In order to have the dust removed, I had to use the history layers, as explained in this article.

My question is: what is the reason to blur all the image instead of blurring only the desired part of the image?

Answer 1

If you are using the dust and scratches filter try to keep the radius to a small number (around 3 or 4 pixels shoud be a good number to start) and increase the threshold gradually until you get the effect you need. If that is affecting parts of the image that you want to leave untouched, then use selection tools (or masks) to apply the filter on specific parts of the image.

The dust and scratches is not a magic wand that makes all of the problems disappear, you might also need to use a healing brush. Make sure that you don't use a brush that is too big, so that it doesn't affect unwanted sections of the image.