How to remove dust spots

Wed 21 May

We show you how to use your image editor's spot healing tool to remove those annoying dust spots on your digital photos

If you use a DSLR, sooner or later you’re going to find yourself swapping lenses - that kit lens that came with the camera isn't going to do all the jobs all the time. That means, sooner or later, you’re going to find yourself facing a problem that photographers have faced since the advent of interchangeable lenses: dust.

Dust is a huge problem: it’s next to impossible to prevent, hard to get rid of and it ruins the best of shots. Many recent DSLRs have self-cleaning sensors to try to minimise the problem, and some can have custom dust maps created so that dust spots are removed in-camera, but knowing how to use the heal tool to get rid of those conspicuous dark spots is a must.

This shot has it all. White, powdery sand, blue skies and… a pair of horrible dust spots, ringed in red. Most likely the spots are hangovers from a less-than-sympathetic lens change, but we’re stuck with them now.

The first thing we need to do is see how bad the problem is by zooming in. We’re in luck: dust spots are hardest to invisibly remove if they’re covering an area of particular interest or detail – a person’s face, for instance. In this case the dust spot occurs in an area of sky, and so, once you know what you’re doing, will be a doddle to remove.

This is the spot-healing tool. This screengrab is taken from Adobe Photoshop, but it’s a standard tool found in most decent photo-editors.

There are several different ways of using the spot-healing brush, but don’t be intimidated: it works just like any other Photoshop tool. Here you can see the most important variables: the size (diameter) of the brush and its hardness.

Spacing simply means how many times the brush is applied when you drag it over your canvas – one per cent means it’s constantly applied; the larger the percentage, the less frequently the brush is applied.

The angle and roundness of your brush will depend on the size of the spot you’re going to remove. Because most dust spots are very close to the focal plane of a camera (i.e. they’re between the lens and the CCD), they appear as fairly round, out-of-focus spots.

But remember that you can easily use the spot-healing tool to correct other image problems, such as blemishes on people’s faces. When dealing with irregularly-shaped problems such as these, the angle and roundness of the brush becomes a factor.

The trick with removing dust spots and blemishes – as with most photo manipulation – is to do it in as few steps as possible. The more work you do, the more likely your efforts are to be visible in the final image. With these dust spots, which are luckily fairly round, we’ll aim to get the job done with one click.

To that end, we’ve tuned the brush so it’s about a fifth larger than the area we’re trying to correct.

Note: The spot-healing brush doesn’t need you to select an area of canvas to sample pixels from – it does this automatically.

Notice that our brush has slightly soft edges. In this case we’ve set the hardness of the brush to 83 per cent. If your brush is 100 per cent hard, you can end up with a peculiar-looking coffee-mug effect, particularly if your brush size doesn’t totally cover your working area.

And with a single click, you’ve done it. This kind of editing takes a few goes to get right – make the CTRL-Z (Undo) shortcut your best friend, and remember that perfectionism is a trait of all good photographers.

If your editing is evident to you on your PC screen, heavy-handed healing can make your shot look worse than if you’d simply left the dust spots alone, so make sure your job is invisible by the time you save.

The finished, healed image. Both of our dust spots have been healed away with single clicks, and the final print looks pristine. Don’t forget it’s possible to take preventative action to keep dust spots from reaching your shots in the first place: be careful where you change lenses (never outside), and treat your camera to a hand-pumped air blower if you notice problems.

If you find dust spots appearing on your prints, give the mirror box (what you see when the lens is off) a few gentle puffs of air to dislodge any major particles. A final word of warning: leave sensor cleaning to the professionals!