Today’s Question: I look forward to experimenting with the new Dust Removal functionality in Camera Raw. I occasionally see dust specks that I know are on the sensor, and they appear as sharply defined spots in the image. But I also frequently get diffuse spots, usually visible only in skies and other plain fields, and my suspicion is that these are caused by dust on one of the physical lens elements, possibly internal to the lens. These are more pronounced with smaller apertures. Does the Dust Removal tool help with both scenarios? And does it help with dust that appears in digital scans from film?
Tim’s Quick Answer: Yes, the Dust feature for Distraction Removal in Camera Raw does clean up both relatively sharp and relatively diffuse dust spots that appear in an image.
More Detail: Dust spots in an image are almost exclusively caused by dust on the image sensor, which is to say dust that attaches to the filter in front of the physical sensor in the camera. Dust on a lens element is not likely to result in what we would classify as a dust spot, though dust on a lens can result in bright orbs in the image caused by the refraction of light.
The difference between relatively crisp versus diffuse dust spots generally relates exclusively to lens aperture. In addition to affecting depth of field, the lens aperture affects depth of focus at the image sensor. Thus, when the lens is stopped down dust spots will appear sharper and when the lens aperture is more open the dust spots will appear less sharp.
Fortunately, in both cases my testing has shown that the Dust feature for Distraction Removal in Camera Raw does a great job identifying and removing these spots. This is especially true for spots that appear in relatively clean areas of an image, such as the sky, because those spots stand out more readily in those areas.
And as I’ve stated previously, I fully expect that the Dust feature will be added to other Adobe applications, including both versions of the Lightroom desktop applications. I have no idea when this might happen, but I’m confident that it will, as Adobe has a good history of maintaining parity across their professional tools for photo editing.
