How to do Exposure Blending Using Luminosity Masks

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There will be a time when the wizards behind your camera technology conjure up a sensor so powerful they will swallow up any scene and spit it out just as it was – no over, or underexposed areas. Until then, in order to produce an image with a high dynamic range of light, you have to work with the sensors available to you and create your own post-processing magic.

Pink sunset

Image created by blending two exposure with luminosity masks, one for the sky and one for the foreground.

While you, and many photographers, may have relied heavily on HDR programs in your exposure blending quest, many more are now beginning to turn to luminosity masks as a cleaner alternative. Through the use of luminosity masks you can create stunning, balanced images that encapsulate a vast dynamic range of light. They give you incredibly fine control over your imagery in almost every area.

While some HDR programs nowadays produce very natural, clean HDR images, luminosity masks do not affect the original files at all, so there is literally zero image degradation during the blending process. That is why so many digital photographers are beginning to make luminosity masks a staple in their workflow.

What are Luminosity Masks?

Luminosity masks break an image down into various channels of luminosity. In other words, they allow you to make very specific selections in Photoshop based on how bright or dark an area is. Let’s say you were looking at a beautiful nighttime cityscape shot. Everything is exposed correctly apart from the street lights, which are completely blown out. You also have a darker exposure in which the street lights are ideally exposed.

Through luminosity masks you can make an accurate selection of the street lights because you can hone in on their brightness, or luminosity values. With this selection you can simply replace the overexposed streets lights with the correctly exposed ones in the darker image.

What You Need to do Luminosity Masking

Firstly, creating your own luminosity masks is a complex and cumbersome process. However, I have a free Photoshop Luminosity Mask Action Set that will do all of the work for you. You can download it here: Free Luminosity Mask Action Set.

Secondly, it is imperative that you have a good understanding of Masking in Photoshop. If you’re a little bit unsure of the process, you can visit Adobe’s site which has a useful video tutorial for you to follow: Masking in Photoshop.

Which exposures to blend?

Ideally, the exposures you choose to blend should cover the full range of light in a given scene. Your brightest exposure should contain information in the darker areas, while your darkest exposure should contain information in the brightest areas. You are not limited to the number of exposures you can blend. Sometimes, in scenes of extremely high contrast, you may need to use as many as five to ensure a smooth transition between exposures and to cover the full range of light in the scene.

The order you choose to layer the exposures in Photoshop is dependent on your personal preference and the exposures you’re working with. Usually working with your normally exposed image as the base layer will derive the best results, but sometimes you may need to work with a darker or brighter exposure as your base layer.

Once you’ve decided on your exposures and have layered them in Photoshop, you now must decide which exposure you will run the actions on. Generally this will be done on your normally exposed image because it will offer the widest range of usable masks. For example, if you ran the luminosity mask actions on a darker exposure, you would gain a full range of dark and mid-tone luminosity masks, but very few, if any, workable bright masks, because the darker exposure is lacking in highlights. The converse is true for a strongly overexposed image.

Blending Exposures Using Luminosity Masks Tutorial

Today you’ll work with two exposures. One is ideally exposed for the sky and sea (download the underexposed image here), while the other is exposed for the foreground elements (download the overexposed image here).

Original files

You want to combine the sky and the sea in the underexposed image with much of the foreground in the overexposed image. To do this, you need to find a way of selecting the sky and the sea (i.e., the blown out areas) in the overexposed shot. Once you’ve done that you just need to replace it with the sky and sea of the darker exposure.

Steps in Photoshop For Blending Exposures

1. Install the Photoshop Action set

Instructions on how to install actions can be found here: Get Creative With Photoshop Actions

2. Import your two images into Photoshop

Bring both images into Photoshop as layers, placing the underexposed image on top. Align the images by selecting both of them on the layers panel, and going to Edit > Auto-Align Layers.

3. Turn off the top layer

Uncheck the eye on the layers panel next to the underexposed layer. This will make it invisible and ensure that the luminosity mask actions will run on the overexposed layer only.

4. Run the Masking Action

Go to your Actions panel, which looks like a Play button on the toolbar. Open it up and go to the set called JM Luminance Masks. Click on the arrow to the left of that. You will now see an option called Generate Luminance Masks. Select it and press the Play button at the bottom of the Actions panel to begin the process.

Luminosity mask actions

5. Add a Layer Mask to the Dark Underexposed Layer

Now, check the eye next to the underexposed layer, so that it is visible again. Make sure that layer is selected, then go down to the bottom of the Layers panel and, while holding Alt (Option on a Mac), left click the Add a Mask icon. This will create a black layer mask on the underexposed layer, making it invisible again.

6. View Luminosity Masks

To see the Luminosity Masks that you’ve generated, go to your Channels palette, next to the Layers panel (if it is not showing go to: Window > Channels and it will appear). You’ll see 18 monochromatic channels, ranging from Brights 1-6, Darks 1-6, Midtones 1-6. Every one of these channels is a potential mask.

Luminosity mask channels

7. Comparing and Selecting a Luminosity Mask

For this set of images, you only need to use one mask in order to blend the sky from the darker exposure into the overexposed image. In this instance, you’ll need to select Brights 3.

Comparing Masks

Just as with normal masking, the brighter the pixel the stronger the selection. In other words, in the image above, if you used Brights 3 you are selecting much of the sky and sea, but none of the foreground which is completely black. Conversely, if you selected Darks 3, for example, you would only be making a selection of the foreground sand and the poles that lead out to sea.

When choosing the appropriate mask, you are looking to isolate different areas. Therefore, it’s important that the mask you choose has the greatest contrast between the areas you wish to select and the areas you wish to ignore.

For example, if you were working on an image of a nice green field on sunny day, but the sky was blown out and you wished to exchange it with the sky from a darker exposure. You would run the luminosity mask actions and choose the mask where the field was black and the sky was white. This would ensure you would only select the sky and not the field in the foreground.

To turn Brights 3 into an actual selection, you just need to hold Control (Command on a Mac) and click the left mouse button on the thumbnail of the Brights 3 channel. Marching ants will appear to indicate your selection. Press “Control + H” to hide the marching ants.

8. Get Ready to Paint on the Mask

Now switch back to your Layers panel and select the underexposed layer. Make sure you select the mask, and not the actual layer itself.

9. Set up the Paint Brush Tool

Choose the Paint Brush tool on the toolbar and make sure the foreground colour is set to white. Choose the correct brush size. This will depend entirely on the area you’re working with in a given image, but usually, a larger brush is better. A brush size of 2,000 pixels was used here. Set the opacity depending on the strength of the masking you wish to use. For example, with this image, you will mask the sky with an opacity of 100%, but the overexposed areas in the water and foreground will only be masked at 40% opacity. This is because you don’t want to darken the sea too much.

10. Painting or Applying the Mask

Now you’re ready to begin masking. Freely move your paint brush around the areas you wish to affect. Since you are masking with a luminosity mask selection you don’t have to worry about going over the edges. Try varying opacities in different places. Even if your brush opacity is set to 100%, you can still run your brush through certain areas a few times to strengthen the effect.

By holding Alt (Option on a Mac) and clicking on the layer mask you’re working on, you can see exactly what the mask now looks like. The image below is the final layer mask after you’ve finished painting. Remember that white equals visible and black equals invisible. So the sky in this layer is completely visible, the sea is grey so it is partially visible. Since the foreground is black, which means invisible, you will be left with a foreground that is 100% from the overexposed layer below.

Final Mask

After a small contrast adjustment and a selective vignette added, here’s the final image along side the original overexposed image you were working with.

Final images

You now have a nicely balanced image with a good range of dynamic light and tones.

Deleting the Luminosity Masks

While working in Photoshop, the more layers you work on, the larger the demand on Photoshop and your system. Large workflows can seriously slow down your operating system. To ease the load, you should delete the luminosity masks once you’ve finished working with them.

To do this, go back into your Channels palette and select Brights 1. Then hold down Shift and press your left mouse button on Brights 2 to select this too. Do the same with each luminosity mask below. Once all are selected, click your right mouse button on any of the selected masks and choose the Delete Channels option. This will remove the selected channels.

Summary

At first, luminosity masks seem complex and sometimes daunting, but in truth, this whole workflow took less than 5 minutes. After a little bit of practice you begin to get an intuitive sense of how to use these powerful tools, and once you do, you gain extensive control over your images that can change your photography forever.

Have you tried this method of blending images, if so share your thoughts or images in the comments below. Or do you prefer the HDR tone-mapping process? Do you think HDR is dead or maybe it should be? Or perhaps you are somewhere in the middle in the 10 steps every HDR photographer goes through? What are your thoughts?

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Jimmy McIntyre

is travel photographer currently undertaking a 2-year project is Asia, writing two photography guidebooks for China and South Korea. He has taught digital blending workshops on 3 continents, and also offers online training. You can download his free Easy Panel for Photoshop, which will create Luminosity Masks for you at the click of a button. If you’d like to take your Luminosity Mask mastery to a new level, check out his comprehensive Luminosity Mask video course.

  • PDawg

    A deceptive headline. This is a nice ad for the action set, but it’s worthless as a tutorial on making luminosity masks. You could at least explain the theory behind luminosity masks, if not describe basically how to make them.

  • Hi there, I’m sorry you feel that way. The title of the tutorial is teaching how to blend exposures and that is what the article focused on. We gave you the free download for the action set in the article in order to save you from having to create your own, which is a 15 minute process. However, an article on how to create your own luminosity masks may be beneficial in the future. In the meantime, this video offers a very good explanation: http://www.youtube.com/watch?v=3XCa3LtsWrY

  • I’m happy to answer any follow up questions 🙂

  • Karl

    Great article! Been thinking about looking more into luminance masks. This helped a lot.

  • PDawg

    Thanks. That really helps.

  • Nice read! I’ve started to get more into HDR photos for the simple purpose of saving details that my camera isn’t capable of capturing. I very much dislike the stereotypical HDR look that has become popular and instead prefer to keep my photos very natural looking. The idea of relative luminosity is important to me. (here’s a blog post by Ian Plant on the idea of relative luminosity: http://www.ianplant.com/blog/2012/09/12/hdr-images-the-importance-of-preserving-relative-luminosity-tones/#sthash.ECGPj1Bn.dpbs)

    As a result, I don’t like using “automatic” HDR software because I end up spending more time trying to fix it later than is worth it. I have however, started using the 32-bit HDR process (Photoshop) and doing the majority of my processing in Lightroom on the 32-bit file where I can control the luminosity better on my own.

    I do really like the concept of luminosity masks because it would allow me to paint the effect in exactly where I want. It is a more controlled manual blending process that could save a lot of time. This manual blend took quite a lot of time to complete and would have greatly benefit from this style of workflow. https://www.flickr.com/photos/jdlais/13039462254/

  • Dave Lindey

    Ive downloaded the action set and the example images and tried to follow through the exercise but something is not working properly at the step 4 where I try to generate Luminance Masks. The action starts but I am prompted to save selections. Not sure what I am not doing properly.

  • Hi Dave, would it be possible to record the screen, upload it to dropbox (or somehwere similar) and send it to me via my contact form so I can see what you’re doing? http://www.throughstrangelenses.com/contact-me/

  • By the way, Dave, please make sure the little square to the left of the action is blank. If it isn’t, just click on it and press okay.

  • Michael Owens

    Very nice tutorial. This used to be my way of doing almost HDR type combinations back in the day. So to have someone else showcase it here, is a good feeling!

    Painstakingly boring task at times, but well worth it!

  • How so? It provides a free action to try this to see if you like the method. Making them is beyond the scope of one article. I think this gives a good overview of how to do it. In fact I followed the directions and tried it myself before publishing the article. I wanted to make sure it worked and was easy to follow. I got this result – lighter one is before, darker one with richer colors is after masking.

    I personally liked having the action provided. Why reinvent the wheel? You still have to choose which mask to use and do your blending. This takes half the work out – why would you want more work? I want to streamline my workflow not add to it, which is why I hadn’t tried this method before. Now I may use it more often. Thanks Jimmy!

  • Gaz Prescott

    Fantastic tutorial and thanks for the actions download. I love creating HDR using manual blending rather than letting a program decide how to blend the exposures and I see using these tools will allow me to do so but just as quickly as using a program… best of both worlds! =)

  • prijam pradhan

    This is great tutorial man . I was wondering if u have a youtube channel 🙂

  • Karen Adams

    Just curious if this will work in Paint Shop Pro as I don’t have Photoshop…as cost is out of my price range!

  • Tony Kuyper

    One of the earliest Internet tutorials on luminosity masks
    is here: http://goodlight.us/writing/luminositymasks/luminositymasks-1.html

    It was published in 2006 and many internet articles about
    using luminosity masks in Photoshop appear after this one and frequently
    reference it. Jimmy McIntyre actually purchased these tutorials and the accompanying Sean Bagshaw videos on 5 March 2013, so they may have had some influence on his own work with these techniques. The tutorial reviews in detail the process for creating luminosity masks. Other free tutorials on the site explain how to use them.

    Luminosity masks do take some practice to use effectively. While they can
    create some beautiful effects that blend seamlessly into the rest of the image
    due to the self-feathering nature of the masks, they also require intentional
    effort on the part of the photographer using them to achieve the desired results. In other words, they’re not a one-click solution to image processing. But that’s
    actually a good thing. Using luminosity masks to facilitate image adjustments allows photographers to touch the light in a very personal way and to create stylistic unique images. They’re very good at helping to get the image to look exactly the way you want it and are worth considering if you understand masking, adjustment layers, and painting in Photoshop.

  • Hi Tony, I did indeed buy this course and found it a wonderful resource. I often recommend it as an accompanying course to my digital blending series.

    Jimmy

  • Hi Karen,
    I’m afraid I have no experience with Paint Shop Pro, so I’m not able to help.

  • Kimberly

    Would this work with Photoshop Elements or Lightroom? Thanks!

  • Thanks Prijam, this is my youtube channel: http://www.youtube.com/user/TheJimmymac20

  • That’s great to hear Gaz. LMs definitely give you more control in exposure blending than anything else.

  • I’m afraid neither Lightroom nor Elements support luminosity masks right now, Kimberly

  • I forgot to mention how much I love the Sharpening For Web actions on your site 🙂

  • okane

    I was considering NIK or One on One to do this type of post processing. Would I be better of using Photoshop?

  • hdc77494

    Karen, you can get Photoshop and Lightroom in Creative Cloud from Adobe for ten bucks a month, I find that very affordable.

  • Hi Okane, Nik and onOne are plugins that require Photoshop/Lightroom. Neither can blend exposures using luminosity masks, but Nik’s HDR Efex can create very natural HDRs. If you’re a complete beginner to HDR and exposure blending, it may be less daunting to use HDR software like Nik HDR Efex rather than luminosity masks .

  • Great information about blending with luminosity masks Jimmy. I will use this for sure.

  • LesBoucher

    It is a shame that those of us who can’t afford Photoshop, and have to work with elements, don’t have the option of actions. 🙁

  • Alex Boel

    Great article! After reading it, I installed the action in CS6, let it run but got instantaneously following message :
    “The object “channel Alpha 1″ is not available at this moment.”
    No idea what’s happening.
    Someone here has a solution for this?
    Tkx

  • Hi Alex, this usually happens when you’re not using an English version of Photoshop. This may help you translate the actions: http://www.kyrsoft.com/

  • Thanks a lot Nick.

  • Alex Boel

    Great article! I installed the action in CS6 but receives error messages that “Channel Alpha 1” was not available!

    Someone a solution to this? Tkx.

  • Alex Boel

    Tkx Jimmy for your solution.
    After a few translations it works.
    What a time saver this action.
    Great job.

  • Neil JJ

    This isn’t cool man. This dude’s written a cool article and you’ve spammed it with yours.

  • Jason Teale

    Love this tutorial. I am actually working on a few images right now using this as a guide. Thanks again for this Jimmy and lets get out and shoot some time soon!

  • Karen Adams

    Ok.

  • Karen Adams

    Thank you. I will check it out.

  • Broseph of Arimathea

    The new version of Elements has alpha channels, so you can build luminosity masks without the action set.

  • Robert Richman

    Hey Jimmy, I think this is a GREAT tutorial and action. I can’t wait to try it out. I reacently downloaded a trial version of Photomatrix, but haven’t tried it out yet. I think I’ll be much happier going with your route better though. Thanks for the free action.

  • Adam

    Same problem here. Any solutions? Also, where did you guys put the ATN file?

  • Here’s the link I shared with Alex: http://www.kyrsoft.com/

    This error comes up when you’re using a non-English version of Photoshop, in which case the actions won’t run unless you translate them first.

  • Steve Triplett

    Can anyone tell me what I am doing wrong? When I try it this is what I get

    https://www.flickr.com/photos/40426813@N07/14284611532/

  • JoshP

    I DL you luminosity mask and was tinkering around with it and found that the selection wasn’t working when I went and brushed over the selection areas outside would also be effected. why is that?

  • JoshP

    and yes I am painting on the mask layer

  • shank

    Hi Jimmy. I bought your masterclass packs. Havent gone through them yet, but just a question. In some scenes where there are lots of grey, how do you advise to do the blending? I tried to do it using this tutorial, but it turned out the colours looked very weird, if you know what I mean. As I was not able to completely choose the particular luminosity as it was not white or black.

  • Hi there, if you’re working with an image comprised mainly of greys in your masks, this means you have a large amount of midtones, and possibly no over/under exposed areas. If this is the case then there is no need to use luminosity masks to blend exposures since you have nothing that you need to recover. Instead, you could probable recover the highlights and shadows in such a scene using just Adobe Camera Raw or Lightroom.

    LMs in exposure blending work when you have noticeable areas of contrast. I hope that helps!

  • shank

    Hey Jimmy. Thanks for the fast reply! Sounds like you are correct. The scene is actually of a lit bridge, and the walkway leading up to it. I made two shots, one where the foreground can be seen, and one where it is totally in shadow. I wanted to blend the visible foreground with the bridge in the darker shot. You are saying that I can achieve that by just using one shot?

  • That could be the case. Try opening the file (must be a RAW file) in ACR, and pulling down the Highlights, while pulling up the shadows and see if that offers you a balanced scene without too much noise.

    If that’s the case then luminosity masks may not be necessary here 🙂

    Cheers

  • shank

    Alright I’ll try that. Thanks again!

  • namik

    Amazing article Thank you .
    ????? ?????????? ????????

  • clearwater

    Does the luminocity masks course work on PSCC that was recently updated early July ?

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