Guest Post: Exposure Blending by Younes Bounhar

All text and images are provided courtesy of Younes Bounhar and are protected under copyright laws.  I invite you to link to this article but please do not re-post the content without prior approval from Younes.  A huge “thanks” goes out to Younes for writing this article and allowing me to publish it on my blog.

In this article, I would like to discuss an alternative method that can not only replace GNDs in some circumstances, but offers significant advantages over both GNDs and the automated HDR options. This technique involves blending multiple exposures using masks and layers in Photoshop. Now, I don’t mean to re-open the debate of “getting right in-camera vs. take it and fix it later approach”. Neither do I pretend that this option is the end all be all, mother all of all options. If you dislike spending time on your computer, this is probably not for you. If on the other hand you believe that you should use every tool you have at your disposal to make the best image you can, then buckle up and jump on board!

Enter Exposure Blending

Let me first start with a disclaimer: as I indicated above, this is not a panacea, or some miracle recipe. Exposure blending is very useful but does have some limitations: it simply does not work with scenes containing moving objects. Also, when dealing with trees or grasses blowing in the wind, it can get tricky and sometimes even unworkable. That said, I find that exposure blending beats HDR programs by a long shot because the results are more realistic looking (personal choice here) and it avoids the muddy toned images that HDR programs often result in.

The Setup

So, what is exposure blending exactly? As its name suggests, it involves taking several exposures of the same subject and “mixing” them in Photoshop using layers and masks.  It is imperative that the framing be identical for each exposure, so it is important you use of a tripod, and ideally a remote release to minimize vibration and motion. The exact bracketing required varies from scene to scene and depends in great part on the dynamic range of your camera. Using my Nikon D700, I simply set it on “matrix metering” and take 3 exposures: 0, -1 and -2 stops. If you are just trying your hand at this, I would definitely recommend trying at least +2 to -2 brackets (5 images total), then adjust accordingly once you get more comfortable. Ultimately, however, only two exposures are usually necessary (0 and -2). I will sometimes blend in parts of a third one if I need more details in the shadows, but that is rarely required.

Blending Exposures

Now on to the blending.

1)  Once the images are uploaded on the computer, process each exposure separately in RAW then open both exposures in Photoshop (here 0 and -2 stops).

2)  Go to the darker exposure, select all (command+A), copy (command+C) and paste it on top of the lighter image (command+V).

3)  Select the top layer (dark) and while pressing the alt button, click on the “add layer mask” button.  This will create a “see-through” mask that will come in handy later to “paint-in” details from the dark exposure onto the lighter one.

4)  In the layers panel, select the channels tab.  Photoshop allows you to create a selection based on the luminosity values in the image. In essence, at the click of a button you can select all the “light” pixels. You can do so by pressing the command button and simultaneously clicking on the RGB channel icon.

5)  You should now see a set of “marching ants”, indicating a selection appear on your image. While this can be used as your mask, I find that going one step further will provide an even better selection. To do so, press shift+option+command and click on the RGB channel icon one more time. This will intersect the previous selection with itself and select a narrower set of light values. You can repeat this as many times as you want, but I find that two selections (step 4+5 combined) are sufficient.

6)  Now move back to the “layers” tab and make sure to select the dark mask we created earlier in step 3, by clicking on it.

7)  Select the eraser (press E), select a large brush (400 px) with 0% hardness and ensure the opacity and flow are set at 100% (top panel). Make sure that black is your foreground colour (you can toggle between foreground and background colours by pressing X, if black is not already one of your colours, press D to revert to default colours, then press X to select black).

8)  Here is where the magic happens: simply start erasing over the overexposed portion of the image (sky and/or reflections for example). You will now see that the darker layer is literally being painted over the lighter one. Because the selection is completely self-feathering, you need not worry too much about being very precise with your painting. I usually find that a few passes with the eraser are necessary to bring all the colours out. Notice that while the sky is being uncovered, the areas in the shadows (e.g. buildings or foreground) are hardly touched.

9)  That is it. Once the result satisfies you, you can merge your two layers and continue on with your usual post processing routine.

10)  If you feel that you are still lacking a bit of detail in some of the shadow areas, you could use an overexposed frame (+1 or +2) to paint in the necessary detail. To do so, simply copy the overexposed frame on top of your other layers. Then, create a “see-through” mask as done in step 3. Select the Eraser, set the opacity between 25 and 40% and flow at about 50%, make sure your foreground colour is black. Then select the mask and start painting over your image in the areas where you would like to reveal more detail. Since the opacity of your eraser is low, multiple passes may be required to achieve the desired result.

The process may sound a bit daunting at first if you are not familiar with masks and layers but once you give it a go you will see that it is fairly straightforward and the results will surely speak for themselves!

About Younes:

Younes Bounhar is a ridiculously talented photographer and super nice guy from Canada.  He offers group workshops and fine art prints, and is a frequent contributor to Photolife magazine.  I encourage you to visit his website for inspiration and check out his blog for a steady stream of helpful information.

18 thoughts on “Guest Post: Exposure Blending by Younes Bounhar”

  1. Thanks Bret. This is a well written article. I have tried other approaches that work reasonably well. Will try this one also. Getting the final image to appear natural is the final test.

    Bill Brennan

  2. Thanks for the comment, Bill. I have tried a few techniques with various levels of success. This technique has worked the best for me. Image blends are an awesome tool & can really enhance your photography if you take the time to learn them. Please let us know what you think of the technique after trying it out.

    1. Hey Paul,

      Glad you found the article useful. I did too! It’s an excellent technique and not a terribly difficult one to use. Definitely a big “thank you!” to Younes for writing it and allowing me to post it.

    1. Thanks, Joe. I’m glad you’re finding some useful information here. It’s all quite random but my goal is to post things I’ve learned and/or found useful in the hope that others will also find value in it. If you have ideas for a topic you’d like to see covered please send me an email. I’m always open to suggestions.

  3. I tried it and gave up at #4. In my version of Photoshop (CS4), there does not appear to be an “add vector mask” button. I think I added a vector mask via the pull-down menu, but in the next step I was supposed to find a channels tab on the layers panel, but my layers panel didn’t have one. I opened a channels panel, but then I was supposed to press the “command button.” PC’s don’t have a command button. I gave up with six more steps to go.

    I was hoping to give it a try to compare the method with a very simple-to-use Lightroom plug-in called Enfuse, which can be had for a small donation to its inventor, and which delivers none of the cartoonish effects seen in so much HDR work.

    1. John: We discovered a typo in step #3 this evening. I’ve since changed it but in short, it used to say “add vector mask” which is incorrect. It should read “add layer mask”. I’m REALLY sorry about the confusion this caused. You weren’t the only one who had some trouble with it. Give it another shot using a layer mask and I think you’ll like the results. Also, thanks for mentioning Enfuse. I’ve heard a lot of really good things about it but have yet to try it out. If you do try this method again I’d be super interested in seeing a side by side comparison of an image processed in Enfuse and the same image blended using this method. Thanks again for pointing out our error. Much appreciated!

  4. Thanks everyone for the kind comments. I would also like to apologise for the error regarding the vector vs layer mask…
    John, with respect to the difference in key commands between PC and Mac, my understanding is that the Mac “command” button is the equivalent of “control” in PC speak. Similarly, “option” in Mac is equivalent to “alt” on PCs. I hope this helps.

    Cheers,

    Younes

  5. This is a marvelous technique. It is not only automatic, but precise and leaves the photographer in complete control. If you paint everything in black, then decide later that a section needs a lighter hand, you can retouch that area with a bit of white, or you can paint with a shade of gray initially. My practice shot had lots of bright areas within the dark shadowed portion – a challenge to get right in the manual method that I have used for a couple of years. I was astounded at the ease and accuracy by which Younes’ technique walked through this. Thanks so much for posting this Bret, and thank you Younes for your great work!!

    1. Looks like the technique worked beautifully for you, Greg. Love the image! That sweet, golden Sonoran desert light that I miss so much. Glad you found the tutorial useful and thanks for sharing an image.

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>