Dust spots are the curse of the landscape photographer, and anyone who ever shoots outside of a studio environment will probably have to deal with them at some point in their artistic career. It’s always nice to have a completely clean sensor, but if you ever have to change your lenses outside of a camera factory’s dust-free ‘clean room’, you’ll probably wind up with some dust on your sensor.
Even if you manage to keep the sensor of your camera clean, it’s still a constant uphill battle to keep the glass elements of your lens perfectly clean, especially when you’re on-location for a shoot out of doors.
Over time, this can be incredibly frustrating. There’s nothing like capturing a perfect shot only to take a look at the image full screen on your editing workstation and finding a nice big dust spot over a key image element. Fortunately for all of us who love to shoot in the field, it’s actually fairly easy to remove them using Photoshop.
Those of you used to working in Lightroom will no doubt already be familiar with the Visualize Spots tool, which makes it quite easy to detect any kind of visual abnormalities in your image such as strange colour areas or dust spots.
For whatever reason, Photoshop has yet to incorporate a similar tool into its capabilities. There is a filter titled ‘Dust and Scratches’ in the Filter/Noise menu, but it’s more designed for removing scratches and other elements from negatives and other scanned images. Unfortunately, it’s also not very good at it’s job. It’s much easier to do it all by hand, with a little bit of creative use of filters and adjustment layers.
Sometimes, it’s quite easy to notice dust spots and specks on your photographs. A little grey blob in the middle of a pristine blue sky stands out like a sore thumb, but they can be much more difficult to spot on more complex and varied backgrounds. Not only that, some dust spots are much harder to spot than others without doing some adjustments first. There are a number of different methods that can be used to reveal them, so let’s take a look at some of the more popular ones.
Probably the simplest way is to start by increasing the contrast of your image dramatically. Obviously you wouldn’t want to leave your image in this state, but it’s quite helpful as a temporary guide for locating trouble spots.
Typically, Curves is the best tool for making any kind of subtle contrast adjustment, but in this one case it can actually be a bit too powerful. This is probably the only situation where it can be easier to use the Levels adjustment tool instead. Paradoxically, sometimes a dull knife is better for certain jobs!
If you’re unfamiliar with it, Levels also allows you to adjust contrast in your image, just with quite a bit less subtlety than you get from Curves. Make sure you use it as an adjustment layer, so you won’t permanently affect your image.
Set up your adjustment layer, and go to the Levels properties.You’ll note that the tool only has 3 sliders – black, grey and white. We want to adjust the grey (midtones) slider almost all the way to the right.
As we do so, you’ll notice that any dust or other distortions become rapidly visible, as you can see below in the sky area of the image. Your mileage may vary, depending on the image you’re working with, but you can experiment with the settings to find what works best for your particular image.
Of course, if you’re more comfortable using Curves, you can achieve a very similar effect, as you can see below.
Once you’ve identified the trouble areas, you have several ways to remove the spots. You can use the Healing Brush tool to remove them, or you can use a selection tool to select them all and fill them using the Content Aware Fill tool. This last is probably the quickest and easiest method, but again, it will depend on the image and what’s underneath the spots.
Some people prefer to use one of a range of filters that adjust the image in various ways, such as Solarize, Find Edges or Emboss, but these are rather clumsy solutions that make it fairly difficult to follow up. Using the Emboss filter, as shown here, does just as good a job of finding the trouble spots in the sky areas, but due to the offset of the filter it makes it a bit more difficult to translate that into the exact locations of the trouble spots.
Bonus method: One of the most accurate ways to remove the exact dust pattern unique to the combination of lens and camera you used during a particular shoot is to take a reference photo. If you have a piece of white paper, simply take a flat shot of it using a proper exposure, and you have a really simple and easy guide to where any dust might be located.
You can keep that file as a reference file, and load it in as a separate layer in any image that you want to edit to help you identify what needs to be fixed. Of course, the dust patterns can change over the course of a shoot, but it can still be quite helpful for identifying specific potential trouble spots
If you get sick of cleaning up dust in Photoshop, the best way to avoid it in the first place is to ensure that you keep your equipment as clean as possible. Never try to clean the sensor yourself unless you have the proper tools, as it’s incredibly delicate and very easy to damage. You can purchase kits that are designed specifically to clean sensors, so check around online or your local camera store to find one that works with your particular camera model.