HDR Tip #7 – Magic Blue Sky Halo Removal
by Dave Wilson on Mar.06, 2011, under Photography
Here’s the last of my HDR tips for this week. I’ve been saving this one for a while but, if you shoot in climates where you can rely upon clear blue skies, it’s a killer tip and could save you hours (even if I do say so myself).
Do you often find yourself with a mess like the following after tone-mapping? Frankly, this is an image I really don’t like – the tone mapping is wildy unsubtle but it serves as a great example for this tip.
The foreground looks the way it was intended to look but the sky is a horrible collection of haloes and weird areas of different shades of blue. Wouldn’t it be great if I could just drop in a new sky without having to spend a week masking around all those blasted leaves? Well here’s a tip that will fix your sky in about 2 minutes flat as long as it’s predominantly blue. This will work if there are some clouds but it definitely works best when the sky is clear.
Take a look at the original brackets you used and decide which one has the best sky tone. I typically like the -2EV image since I like nice, dark, saturated skies but it’s entirely up to you. Open the tone mapped image and the original image with the good sky as layers in Photoshop with the tone-mapped image below the original bracket.
Now we’re going to use a bit of magic that very few people seem to know about. Make sure your magnification is set so that you can see the whole sky area of the image then right click on the top layer (with the original image) and select “Blending options…” (in CS5 at any rate. It used to be called “Advanced Blending…” or something similar in some previous versions as far as I can remember and you accessed it from the layer effects list I think). The dialog that you will see allows you to control how this layer blends with the one below it and one of the great features it offers is the ability to blend based on the colours in either this layer or the one below it.
As you will notice, the bits of the tone-mapped image we want to replace correspond with the blue sky in the original image so let’s tell Photoshop to show the original only where it is predominantly blue. Do this by setting the “Blend If” option to “Blue” then drag the slider under “This Layer” to the right. As you do this, you will see that the underlying layer starts to bleed through and become visible. Move the slider to the right until you start to see chunks of the tone-mapped sky appearing then stop. At this point, you will notice something along the lines of the following:
The original sky is definitely visible but you will also see a lot of really horrid fringes around all the tone-mapped leaves. There’s another secret to get rid of these. Hold the “Alt” key and click on the slider you just dragged. You will notice that it splits in two so now grab the left hand half-slider and pull it back towards the left. As you do this, you should see the fringes get smaller and, eventually disappear leaving you with something like this:
You will likely have to juggle the left and right half slider positions to get the best overall effect. It’s a good idea to zoom to 100% to check out the fringes since it’s tricky to see how the individual leaves (or other edges) look when you are zoomed out.
Once you have marveled at how the sky looks, you may be disappointed to notice that this blending has had a muting effect on other sections of the image too. This can, however, be corrected very easily by adding a layer mask to the top (original image) layer and, using a soft-edged brush, painting in black over the areas that you don’t want to be affected. Doing this, you are effectively allowing the underlying tone-mapped layer to shine through completely unaffected. If you accidentally paint any of the sky, just switch to white and paint the mask with that to erase the effect. Typically, the effect on non-sky sections of the image is reasonably subtle so you don’t have to be enormously careful when you are doing this final masking step. Painting this mask is, of course, enormously easier than trying to figure out how to mask around all the leaves!
Here’s the final version of the image I started with after about 2 minutes of slider juggling and some easy mask painting.
Hopefully you’ll find this tip useful. It’s saved me hours here in Texas where blue skies are the norm. If you live up north or across the pond, you may find this less helpful but the basic approach can still be used for many other cases where you want to blend based on the colour of particular regions of an image.
I hope you’ve found this week of HDR tips helpful. Thanks for reading!
17 Comments for this entry
3 Trackbacks / Pingbacks for this entry
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March 13th, 2011 on Mar 13, 11 | 7:35 am[…] I also wish I lined up the panels a little straighter. By the way, Dave Wilson recently posted a great tip on how to fix blue sky halos in difficult situations. This wouldn’t even have been a tough […]
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Why HDR Sucks | News and Views from Dave Wilson
June 3rd, 2012 on Jun 03, 12 | 1:47 pm[…] of problem is straightforward in Photoshop (this image is the example I used in my tutorial on the Magic Blue Sky Halo Removal Method but I was just being too lazy that evening to do the job […]
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Skyscraper « Michael Tuuk Photography
June 5th, 2012 on Jun 05, 12 | 7:04 pm[…] This is an HDR and naturally it bugs me that there’s a slight halo around that tall skyscraper. Â The thing is, that halo is present in the original exposures too. Â Despite the fact that there will be those who attribute the halo effect to “bad HDR”, I decided to leave it as is. Â For those of you interested in one method of fixing this (particularly in difficult, detailed scenes), see Dave Wilson’s handy tips here. […]
March 6th, 2011 on Mar 06, 11 | 8:06 pm
Wow. This is gonna be a lifesaver for me. Thanks so much for sharing this one, Dave!
March 6th, 2011 on Mar 06, 11 | 8:20 pm
My favorite way to fix this issue. We have same challenge in Az. Great tip Dave
March 6th, 2011 on Mar 06, 11 | 10:48 pm
I never knew this. Great tip, and thank you very much.
March 7th, 2011 on Mar 07, 11 | 12:48 am
Dave,
That might be the most helpful HDR tip I’ve ever read!
–Miles
March 7th, 2011 on Mar 07, 11 | 7:35 am
This is very helpful! I know you showed us how to do this at the crash course a few weeks ago, but my notes aren’t so good. Thanks for publishing this! Oh and BTW, your tips are better than the other being put out there this past week!
March 7th, 2011 on Mar 07, 11 | 9:59 am
Great method and tutorial. You’ve inspired me to go back through a bunch of old images and give this a try.
March 7th, 2011 on Mar 07, 11 | 10:30 am
Very useful tip! Halos are the bane of HDR photography. Minimizing or removing them just got a whole lot easier. Thanks, Dave.
March 7th, 2011 on Mar 07, 11 | 1:23 pm
Dave
A lot of HDR tips I see are recycled endlessly. You consistently manage to come up with information I never knew. Well done and thanks.
March 7th, 2011 on Mar 07, 11 | 4:27 pm
You’re very welcome. I’m glad the tips are helpful. I wouldn’t consider myself a Photoshop expert but I’ve been using it for about 15 years and have picked up a few of these tricks along the way.
March 8th, 2011 on Mar 08, 11 | 1:19 am
What a fantastic tip … right, where are all those skies…
March 8th, 2011 on Mar 08, 11 | 6:40 am
Great tip, Dave! We often have bright blue skies here in North Carolina, so it will be most useful. I’ve wrestled with the issue before, but this method looks pretty slick.
March 8th, 2011 on Mar 08, 11 | 1:02 pm
Great tip Dave!
March 9th, 2011 on Mar 09, 11 | 9:19 am
I’m finally catching up on your series. This was a great run. Thanks for taking the time to put this together Dave!
March 11th, 2011 on Mar 11, 11 | 8:49 am
Oh, thanks a lot! I just had a photo with exactly the same problem! Now I manage to fix it!
/Lillianna
May 16th, 2011 on May 16, 11 | 4:44 pm
Thanks for this Dave! I’ve always had trouble with those dame halo’s 🙂
May 20th, 2011 on May 20, 11 | 9:31 pm
EXcellent tip on what its normally a very difficult problem for blue skies — THANKS!
January 12th, 2012 on Jan 12, 12 | 4:45 am
Thanks for the great tip Dave!!!.. I am just starting with HDR, and you have been helpful.
THANKS!