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Do It Yourself Dehaze

OK, for me at least, the new Dehaze is cool. But not everyone has joined the Creative Cloud and I've heard from some who want to know if they can get the same results without the real Dehaze. Here's my version of a do-it-yourself Dehaze.

First of all, nothing about image editing is magic. It's digital, and digital means that everything is in the numbers. If you can make the RGB numbers for every pixel in an image come out with particular values, that image will look a particular way. The numbers are the image. It doesn't matter in the least how you got those number to have those values. Whatever it was you did made the image look that way. There are countless ways to manipulate the RGB values in an image. But image files from modern cameras have quite a few pixels in them. After all, they measure image resolution in megapixels, or millions of pixels. And nobody wants to manually edit the RGB values for a million pixels, let alone ten, twenty or more millions of them. The trick then is to find a way that changes the numbers for as many pixels as possible at the same time in a meaningfully helpful way. Otherwise, you'd never finish the task of editing even a single image.

And manually editing pixel values has another problem that is equally difficult to overcome. Unless you're handy with a calculator and possess an intimate understanding of the physics of light and imaging, there's no way you can determine values for successive images across an area that will retain a natural looking gradient. The resulting image is supposed to still look like the original image, but better.

These are both high on the list of why Photoshop and Lightroom each contain so many tools that can change pixel RGB values. Dehaze is just the latest addition to such long lists of tools. Yes, it's enormously convenient for the effect it provides, but it isn't indispensable. There's no reason to feel like you can't achieve the same results without it. It may take a tad more effort, but for this particular purpose at least, you can thereby avoid the Creative Cloud licensing change. This, of course, is a tradeoff you'll need to decide to accept yourself. But what I'm going to describe here will work just fine without the Cloud.

In line with the first of two points I started with here, my goal is to make use of techniques that leverage tools capable of changing the most pixels as possible, as easily as possible. I could just tell you to break out the paintbrush tool set to a very fine brush size and go at it, but would certainly prove unworkable in terms of time investment, but it would also nearly as certainly fail you in terms of creating natural looking results.

Last week, I talked about how the Dehaze tool shared a lot in common with Clarity, the tool many of us previously used to minimize the appearance of haze in troublesome images. So I started there, and since I expected to need Layers and Layer Masks, I did my Clarity adjustments in Adobe Camera Raw. I probably could have used Lightroom, but I wanted to keep my options open for manual tweaking if need be. If you're a Lightroom user without access to Dehaze, I'd encourage you to see what you can do with the tools you do have. For this week's article though, I went with ACR and Photoshop.

The first thing I did as a control for my tests was to open an unaltered hazy image in Photoshop. That image is of Mt. Baker at sunset, looking towards the northeast across the islands of Puget Sound as seen from the top of Blue Mountain in the Olympic Mountains of Washington State. On a perfectly clear evening, this is a great view. But as the crow flies, Mt. Baker is a good 75 miles away, and perfectly clear evenings over that distance are hard to come by.

I also opened a second copy with the single change of setting Dehaze in Adobe Camera Raw to what gave me what I was after. Yes, I have Photoshop CC, but I promise this is the only thing I did here that made use of features exclusive to the Cloud. I only did this in order to have a reference image to compare my manual tweak efforts against to determine how close I could come to Dehaze without using Dehaze.

So, I proceeded to open the original unaltered and raw hazy image in Adobe Camera Raw. Since haze problems generally increase based on distance, I created a Graduated adjustment in ACR and began my tweaking. I pushed the Clarity to the max, and then did the same to the Contrast, Saturation and Sharpness. That may seem like a lot, but I had a lot of haze to cut through. One of the nice things about digital image optimization in general is that you can see what you are doing as you do it. So I watched the image, and I fiddled with the sliders.

Having thereby maxed out what I could do in Camera Raw, opened the image with those adjustments in Photoshop to see what more I could do without a lot of effort. What I had done in ACR was a huge step in the right direction, but a simple push of the Dehaze slider was able to do so much more. If I couldn't get within striking range of that, this whole experiment would end up a failure. Rather than finding a viable replacement for Dehaze I would have proven instead that Dehaze was indispensable. I had to do more.

The other thing a pointed out last week was that the results from Dehaze seemed to be masked based on the brightness of each part of an image. That makes sense since haze limits the black point of an image, wiping out dark areas and replacing them washed out white. If a part of an image retains a useful black point, it probably doesn't suffer from haze. Assuming it wasn't underexposed of course.

There's am easy way to create an image mask based on brightness. First, select the entire image by hitting Ctrl-A on the keyboard. Then copy it to the clipboard via Ctrl-C. Create a new Levels adjustment layer by clicking on the half-white / half-black circle icon at the bottom of the Layers panel. Don't actually adjust any Levels yet, just create the layer so you get the accompanying layer mask. Now make the mask visible and active by holding down the Alt key and left-mouse clicking on the white square for the mask next to your new adjustment layer. The image itself will get replaced by a full-sized white rectangle. The real image is still there of course, but you can now see the mask rather than the image. Hit Ctrl-V to past your copied image into the mask. You should see a black and white version of your image since a mask has just a single channel rather than all three RGB channels. Since a mask is active proportionally to brightness, this gives us what we want. Any adjustments to the levels will affect the areas where the mask is white and not those where it is black. Shades of gray in between will be affected proportionally. To maximize the usefulness of what you created, adjust the levels of your black and white mask to stretch the contrast range from pure black to white. Don't worry about keeping the mask image realistic. Remember it's only a mask.

Now adjust the Levels associated with the new mask to push down the black point. Pull the black point marker inwards towards the center to help restore the missing contrast. These changes should affect only the brighter, washed out areas of the image since mask limits the effects. Our efforts so far are starting to look close to the real Dehaze results, but there's still something missing.

Original unedited Mt. Baker image
Original unedited Mt. Baker image
Real Creative Cloud Dehaze set at 60
Real Creative Cloud Dehaze set at 60
A fairly easy manual Dehaze as described in the text
A fairly easy manual Dehaze
as described in the text

The other thing Dehaze has a great deal of similarity to is sharpening. There's a well-known trick to add local contras to an image by means of sharpening with a high radius value but a low amount. Again, just watch the actual image while adjusting the two Unsharp Mask sliders until you get what looks good. For my image, I ended up with an amount of 22 and a radius of 150 pixels. Your results and needs may vary.

Altogether, this serious of relatively easy edits mimics the appearance of real Dehaze fairly well. And at no time was I forced into manually tweaking individual pixels or even manually painting on the mask or image. Was it more work than simply pushing the Dehaze slider in Creative Cloud? Well, of course it was, but not onerously so. Assuming you don't need to reduce haze in every image, I'd consider this a viable alternative.

Graduated adjustment for manual Dehaze in Adobe Camera Raw
Graduated adjustment for manual Dehaze in Adobe Camera Raw

Of course I do have Photoshop CC and Lightroom CC, both with real Dehaze. Even so, I consider my little experiment to be time well spent. It's forced me think about just what Dehaze does and made me more aware of where it can go wrong. I mentioned last week the potential flaw of Dehaze oversaturating an image. You can see it here too in the top of the foreground rocks that jut out in front of areas that do have inherent haze. You could say that this is just the warm glow of sunset reflecting off the rocks, but it's clearly overdone. My manual experiments here show the same flaws. This can be toned down with a touch of targeted adjustments but that was beyond the scope of what I wanted to address here. The other notable issue with the actual Deahze version of my Mt. Baker image is the ghosting visible around those same foreground rocks. It's only minimally evident in the screen jpeg accompanying this article, but at full size in Photoshop I can definitely see it. If I push Dehaze to the max, it becomes even more evident. Interestingly, my manually dehazed image doesn't show that same ghosting. I think my trick of using the image itself as a mask helped to constrain the levels shift more accurately than did real Dehaze. Score one for manual effort.

Will I give up on using real Dehaze? Of course not. I pay for the Creative Cloud plan so I get to use the good stuff. But Dehaze doesn't need to be reason you upgrade to the Cloud, unless you want it to be.


Date posted: July 5, 2015

 

Copyright © 2015 Bob Johnson, Earthbound Light - all rights reserved.
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