Adobe added a dehaze filter to Lightroom in mid-2015, and it’s been a fixture ever since. In current Lightroom Classic, you’ll find the Dehaze slider in the Basic panel (it originally lived in the Effects panel before being moved in late 2017). The filter is designed to cut through atmospheric haze or mist, giving misty images sharper definition. But it’s also very useful for an off-label purpose: finding dust spots.
Dust on the sensor is an annoying fact of life if you’re changing lenses on the go. Even if you stick to changing lenses indoors (which isn’t practical much of the time), keep the camera pointed down, and do it quickly, chances are excellent you’re going to get some dust or dirt on the sensor. You can make the consequences less visible by shooting at wider apertures, but a certain percentage of your photos are likely to have dust spots on them.
A lot of the time they’re easy to spot. Sometimes they’re more subtle. And even if they’re essentially invisible on screen, they might become more visible in prints or if an end user decides to do further post-processing of their own. There’s also the professional pride in producing images that aren’t marred by dust spots if it’s at all possible.
This is where the dehaze filter comes in. One of its characteristics is that it can exaggerate optical flaws in the image. Most of the time that’s a negative, but it can also be put to good use.
Just like Lightroom’s Visualize Spots tool helps offending areas leap off the screen, the dehaze filter can be used to similar effect. And once you’ve found the spots, you can use Lightroom’s Healing tool (called the Spot Removal tool in earlier versions) to eliminate them. It’s a quick and easy process.
So long as you do this entire process in Lightroom, the dehaze filter is completely reversible thanks to Lightroom’s non-destructive workflow. What you don’t want to do is render the file out to Photoshop or another external editor while Dehaze is cranked up, because that bakes the dehaze setting into the rendered TIFF or PSD and you won’t be able to undo it.
Tip: A quick way to reset any of Lightroom’s sliders to their original settings is to double-click on the slider label.
Examples
Here are a couple of examples where the dust spots were there but were too subtle to be easily seen in the master file. Ramping up the dehaze filter to +100 made them pop. I could then clone the spots away and reset the dehaze slider back to 0.
In this first shot, the overall image is naturally very high-key. It was shot through heavy rain, looking into the distance across the Golden Horn towards Galata Tower in Istanbul.
In the original, the dust spots are basically invisible thanks to the overall highlights. But by pushing the dehaze slider to +100, a number of spots across the top half of the frame become clearly visible and easily squashable with the Healing tool.
Here’s another example where the dust spots are hiding in the thick haze of the sky in the late afternoon in Hue, Vietnam. Turning the dehaze filter up to +100 shows up several others, particularly over in the far left of frame.
In neither of these examples would I leave the dehaze filter cranked up the way I’m using it here. But it’s very easy to reverse, simply by resetting it back to 0.
Why do it this way?
You could use other methods to create the same effect, but they involve much more work.
With the first example, cranking up the clarity and contrast sliders to the maximum and pulling the blacks slider all the way left only revealed one dust spot — the one in the top right. Finding the others required also messing with exposure and highlights. That’s a lot of sliders to remember to reset. The Visualize Spots tool, designed for exactly this job, didn’t show them up either.
The dehaze filter, on the other hand, gave me a one-stop, easily reversible tool to find the spots quickly. It’s not what the dehaze filter exists for, but it’s a handy use for it.
