Dehaze again: what does it actually do?

[DanK]

Has anyone seen an explanation of what the new LR/ACR dehaze slider actually does? Today, while cleaning out old photos (moral of the story, at least for me: the ones that look like they are not worth keeping the first time around often look even worse the second time), I found a shot of a frog half submerged in water, with reflections on the water. Analogous to haze, I figured. So, I played with the slider. I was able to see two things:

1. The slider seems to anchor the top of the histogram but otherwise to shift almost the entire histogram to the left.

2. It increases saturation, quite noticeably at the top, without moving the saturation slider.

Darkening, increased saturation, and pulling the highlights back up after darkening all make sense as a way of dealing with haze, but there has to be more. For example, I assume it increases clarity or does a local contrast adjustment, both of which are similar and conventional things to do in response to haze.

[bugster0121]

Have not used the slider much (yet) and these do not go into great detail but here is a couple links about the dehaze slider.



http://prodesigntools.com/adobe-phot...og-dehaze.html

http://blogs.adobe.com/jkost/2015/06...htroom-cc.html

[davidedric]

"The Dehaze technology is based on a physical model of how light is transmitted, and it tries to estimate light that is lost due to absorption and scattering through the atmosphere".

So says Adobe's blog. Not sure it helps much, though. I suspect there is some fairly fancy maths going on (my memory of Fourier transforms and the like faded long ago). I wonder if it's at all analogous to deconvolution sharpening, where you have to work out what the original signal might have looked like.

I suspect that this is a tool that will go through several cycles of refinement.

Dave

[IzzieK]

Looking through the tutorials available, like Dave, I think there will always be a workaround when you have a hazy image...pretty much what you do in post processing when you shoot through a glass door or a kitchen window...

[FootLoose]

DxO brought out a dehaze slider several months ago. I wonder if Adobe has incorporated / imitated that. In any case, I think it is just a gimmick. As others have stated, it is not something that should persuade people to buy or upgrade PS. Mike, for one, has demonstrated that experienced PS users can achieve similar or better results.

[dje]

So says Adobe's blog. Not sure it helps much, though. I suspect there is some fairly fancy maths going on (my memory of Fourier transforms and the like faded long ago). I wonder if it's at all analogous to deconvolution sharpening, where you have to work out what the original signal might have looked like.

I suspect that this is a tool that will go through several cycles of refinement.

Dave

It's possibly a signal processing algorithm along the lines of that described here. Don't ask me to explain it, it's way over my head !

Dave

[Manfred M]

DxO brought out a dehaze slider several months ago. I wonder if Adobe has incorporated / imitated that. In any case, I think it is just a gimmick. As others have stated, it is not something that should persuade people to buy or upgrade PS. Mike, for one, has demonstrated that experienced PS users can achieve similar or better results.

I also believe Mike suggested what took him hours to do by hand now took a couple of minutes with the new tool. This is much like the "content aware" tools that came out in CS4. Again, hours of work with the clone (and other) tools could be replicated with just a few seconds of work.

[Donald]

DxO brought out a dehaze slider several months ago. I wonder if Adobe has incorporated / imitated that. In any case, I think it is just a gimmick.

Don't know anything about the adobe tool, but the DxO Clearview tool is wonderful. It's got to be used sparingly and slightly. Go too far and things begin to look very artificial. And, of course, it should only be used when you do want to clear haze. Unfortunately, up here on the northern fringes of Europe, we don't have a need for a heat haze control tool on too many days of the year!

[Mike Buckley]

As others have stated, it is not something that should persuade people to buy or upgrade PS. Mike, for one, has demonstrated that experienced PS users can achieve similar or better results.

As Manfred explained, I'm blown away with the ease and speed of using the Dehaze tool as demonstrated by others so far. I haven't used it. I've never used an Adobe product other than to correct perspective distortion, to clone, or to host Google/Nik Silver Efex Pro. Yet I see a subscription to Photoshop CC and Lightroom CC in my relatively near future so I can make use of this tool.

I anticipate a workflow that involves using Adobe's Dehaze tool followed by tweaking using my own post-processing custom presets and manual treatments that generally involve decreasing brightness, increasing contrast and increasing warmth depending on the need.

[DanK]

I spend most of my time in somewhat to very humid environments, so to the extent that I do landscapes, I expect I will use this often, and I'm delighted that Adobe added it. Nonetheless, my first trials suggest that as Brownbear reported in another thread and Donald suggested here, extreme adjustments may in some cases look artificial and overly dark. This isn't surprising. The software is only applying a uniform algorithm to all scenes based on a model of the impact of haze, and it will probably work better in some circumstances than in others. Still, one very impressive piece of software development.

[Mike Buckley]

Great summary of my expectations also, Dan!