Images often need a contrast boost to give them a little more life and intensity. It’s a perfectly ordinary technique we’ve been using for years. Tone curve tools or simple contrast sliders are used to push the bright and dark values in the picture further apart to increase their separation (and, ideally, without ‘clipping’ extreme shadow or highlight detail.
But this is a global technique. With regular tone curve adjustments you can’t increase contrast in one part of the brightness range without reducing it in another. Unless you’ve got some headroom in the darkest and brightest parts of the picture, if you want stronger midtones you have to put up with some tonal compression in the shadows and/or highlights.
But Lightroom’s Dehaze tool has brought another choice. It doesn’t boost contrast equally across the whole image – instead, it boosts contrast in smaller, localised regions.
Lightroom isn’t the only tool to offer a feature like this. DxO kicked off the idea of localised contrast adjustments with the ClearView option in DxO Optics Pro.
Both are like larger-scale versions of the ‘clarity’ sliders now appearing in a lot of image-editing tools.
Dehaze and ClearView are often pitched as tools for improving landscapes, reducing distant haze without affecting nearby details. They’re actually a lot more useful than this – and they have a very different effect to regular contrast adjustments.
Here’s a photo which shows the difference.
This image looks pretty flat. I want to boost the contrast but I’m pretty sure that will knock out the sky, which is already quite light – and I have already pulled back the highlights about as far as they’ll go in order to keep those pale clouds.
So here’s the same photo with a big contrast boost. It’s not bad, but the foreground rocks have become quite dark and the sky is still a little weak. Incidentally, I’m saving these adjustments as Snapshots (left panel) to make comparisons easier later on.
But here is the same shot with a a big Dehaze adjustment applied, and the difference is obvious. The sky now has some real depth and the foreground rocks look strong and vivid too. It’s a bit dark, though…
This is a general effect of the Dehaze filter, so I’ve just boosted the Exposure value a little (while keeping a close eye on the highlights).
And this is the before-and-after adjustment, with a regular contrast boost on the left and the Dehaze effect on the right. The Dehaze version is now a little super-saturated (easy to fix) and in some instances you may see a diffuse ‘glow’ effect where one region meets another, but it’s not obvious here despite the strong adjustment.
I wouldn’t use Dehaze over contrast adjustments on every image because sometimes you want that strong difference between light and dark, but in shots like this where every region is important, Dehaze is an interesting and very powerful alternative.
