Using the Venerable Dust & Scratches Filter (PS and PSE)
This old snapshot of Trudie Ann has already spent a long life tossed in a box with other photos, been dragged around the continent, and stored without care in many different climates. All things considered, it’s remarkably free from serious damage, despite having a lot of fine scratches and a fair number of dust spots. However, I don’t really want to spend hours spotting and healing the entire image using small brushes if I can help it.
Designed before the digital camera became king, the now-ancient Dust and Scratches filter (Filter> Noise> Dust & Scratches) helps speed up cleaning scans that aren’t in pristine condition. The trouble with that filter is it doesn’t know if a light spot surrounded by darker pixels is unwanted or critical detail. High contrast details, such as dappled light in trees or catchlights in eyes, often get muddied by this filter. It’s quick and easy to use, but it will just as quickly ruin an image as rescue it. Still, it was useful back then, and it can be useful today if we know when and how to use it.
Today’s methods for using the D&S filter are easier than they used to be before Healing brushes, the Patch tool, and Smart Filters. For instance, I often used to run D&S at amounts that got rid of most of the spots and scratches, create a Snapshot in the History panel, then step back in History to right before I ran the filter. I targeted the Snapshot I’d just made and used the History brush at a small size to paint the filter back into the image just where I wanted it, essentially attempting to hand paint out each and every spot or scratch without blurring the rest of the image. It was still faster for smallish spots and scratches than using the Clone Stamp tool everywhere (and I felt pretty cool finding a use for Snapshots in the new History panel).
Today instead, I run a very modest amount of the D&S filter on a Smart Object layer, then use the Smart Filter mask that is automatically created to mask the areas where the filter has been too destructive. Or, conversely, if there’s little to clean and a lot of detail to protect, I’ll invert the Smart Filter mask (Cmd/Ctrl-I) and paint with white where I want to apply the filter to the image. I always protect the eyes, even when there’s a spot there. I only remove the smaller spots, which are usually the most numerous, and switch to healing and patching to clean up the rest.
Because running Dust & Scratches on an image softens the entire image, and can require a lot of hand painting on masks to bring back lost edges and detail, I typically use it on images like Trudie Ann, which are already very grainy and lacking in sharp edges and contrast. I don’t mind softening the grain, and I can keep the need for masking to a minimum. If I see it’s going to take a lot of work to preserve my image’s quality, I’d rather go ahead and use the healing and patching tools, along with the Clone Stamp if needed, than start with anything as destructive as the D&S filter.
How much image quality you can stand to see degraded by the filter, of course, depends upon how much time you have to spend retouching it. Dust & Scratches is quick if the image is going to be used at a fairly small size, and once you sharpen the image, it might look just fine. Sometimes an image isn’t worth spending hours on, but that doesn’t mean we want to (or can) simply throw it away, so we compromise and no one gets hurt in the process.
To run the Dust & Scratches filter, I focus on an area that has a lot of little specks, and I don’t worry about scratches or large spots. With Threshold at 0, I move the Radius slider up just a few pixels. If I am not getting rid of the little spots by 3-4 pixels, I will usually give up on the filter. The Threshold slider lets me bring some texture back to the image, but it won’t overcome an obvious loss of detail, and once it has removed blur from too high a Radius setting, you’ll see terrible artifacts. (An idea for creating a weird texture, perhaps?)
Once I see most of the small spots disappear, I bring up the Threshold slider until I see the spots start to become easily visible again, and then move it back down by one or two levels. This time I’m compromising between concealing the spots and retaining enough grain and texture the image doesn’t become plastic and unnatural, which almost always leaves me with some hand work left to do. But thanks to Dust & Scratches, not as much as when I started.