Luminosity Mask Versus HDR Software: The When, Where and Why

By YPLuminosity masks, Tutorials

Most of us share a common path in discovering HDR photography.

We saw an image that we really like -> Found out it was an HDR -> Search the internet and learn everything we could on the topic -> Start shooting everything in HDR + invest in an HDR software.

As time goes by, we begin to unmask the limitation of HDR software and how garish our images can look when we go slider-happy in tone-mapping. Some of us venture out to realize there's something out there call luminosity mask.

hdr or luminosity mask

It's a fact that blending multiple exposures using luminosity mask does produce more natural and realistic HDR. But it takes longer to achieve the result compared to HDR software. However, most HDR software have made improvement in tone-mapping algorithm at the same time.

It's only human nature that we want the best. So, the question now arises:

Luminosity mask versus HDR software: which is the best?

In this article, I share with you why I think each has its own strength and when you should use one or another in different circumstances.

The Ugly Truth

I doubt you'll ever find an agreement to "which method is the best"

Because "best" is subjective. What is best for me may be mediocre for you, and vice versa.

Also, each technique gets us result and has its own strength. When you spare the sliders to avoid the rampant HDR look, it's often hard to tell which image is created with HDR software and which one with blending using luminosity mask.

Look at the images below. One is post-processed with HDR software and one with blending using luminosity mask in Photoshop. Can you guess which is which?

hdr software or blending with luminosity mask?
hdr software or blending with luminosity mask?

Luminosity Mask Vs HDR Software

With luminosity mask, you have complete control over where and how much (layer opacity) you want to blend​. The feathering between the base and the blend layer makes the transition seamless. The only catch is, you need to learn luminosity mask and there's a learning curve.

Learn more: The Ultimate Resource To Luminosity Mask In Photoshop

base layer and blend layer in photoshop

Each blend consists of a base layer and a blend layer. Base layer is always at the bottom of the blend layer. Personally, I prefer to place the darker exposure on top as the blend layer. But you can place it below too, it works in both ways.

The biggest advantage of using an HDR software is its automation. Drop your images in and with a few clicks, you have an HDR image within a few seconds.

Since each method has its own merit, when do we choose to blend using luminosity mask and when to use HDR software?

You guessed it right again.

There's no answer to this question either.​ But I can share what I routinely do with you.

When Do I Use Luminosity Mask?

You can use it to post-process any image you like. Bear in mind that luminosity mask only works in Photoshop and GIMP.

Remember, it's a selection tool. It creates a selection in your image based on the luminosity value you've chosen. Once a selection is made, you can apply any adjustments you like.

In single image post-processing, I use luminosity mask when I want to apply adjustments selectively without affecting other parts of my image. Because of feathering, the adjustments will blend in seamlessly and look natural. Here is what I do:

  1. ​Decide on what adjustment I want to apply and where.
  2. Select a luminosity mask that targets the area I want. Finding the right mask is often a matter of trial and error. But it only takes a few seconds.
  3. Once I found a mask, select it and the marching ants should appear.
  4. Click on the layer that I want to apply the adjustment (this is often the top layer) and apply the adjustment.

In the context of exposure blending, luminosity mask it is always my preferred choice in crafting natural HDR.

I use luminosity mask when:

  • I want to blend in a specific part from another exposure, and
  • Other methods of blending didn't work.

Blending with luminosity mask is a topic on its own. If you're not sure how it works, go ahead and check out this tutorial on Exposure Blending With Luminosity Mask.

Where Do I Use Luminosity Mask?

Most of the time, you blend multiple exposures because you couldn't get the full dynamic range in a single image. So, where you want to select with luminosity mask are the parts you want to blend in from another exposure.

This is often ​the sky (usually over exposed), or parts of the foreground (under exposed). Luminosity mask comes in really handy when the horizon isn't straight or it's crossed by objects (e.g. trees, buildings, etc).

In the example below, the image on the left is the luminosity mask that blended the sky into the image exposed for the foreground (where the sky is over exposed).

Here are the steps:

  1. ​Stacked the images with the image I want to blend in (the image exposed for the sky) on top. Add a black layer mask to conceal the top layer.
  2. Select a brights mask that targets the sky only. The luminosity mask is generated based on the image exposed for the foreground where the sky is over exposed.
  3. With the marching ants displayed, click on the black layer mask of the top layer.
  4. Paint on the black layer mask with a large, soft white brush across the sky in the image. The image exposed for the sky will now be blended in.
  5. I painted across the sky and part of the foreground (you can see the far end of the foreground is revealed). This is to smoothen the transition so the effect looks more natural.

Quick tip: I find blending a darker exposure into a brighter exposure easier than the other way round. Learn more under "Pitfalls" in The Kickstarter's Guide To Luminosity Mask.​

where do i use luminosity mask

The darker exposure was blended in using the "painting a mask" technique.

where do i use luminosity mask

The final image following further tonal and color adjustments after blending with luminosity mask.

Why Should I Use Luminosity Mask?

There are two reasons why I choose to blend using luminosity mask instead of HDR software. Efficiency and image quality

Greater Workflow Efficiency

You want to work hard but you also need to work smart. Spending a good few hours post-processing an image may not be the best for you and your client. You may produce results but it comes with great effort, that's not efficient at all.

If you want to improve the efficiency of your workflow, then you should definitely give luminosity mask a try.

Besides the feathering nature, luminosity mask is so much more precise and quick in making a selection. This definitely saves you time from creating a selection with any of the selection tools in Photoshop.

When blending in from another image, you don't have to worry about "painting outside the line" as the area outside the selection is still masked. Even if the area outside is grey on the mask, the effect is likely to be minimal. If want to be ultra precise, group the layer, add a black layer mask to the group and paint the effect back in.

Of course, you don't always have to blend with luminosity mask. If the area you want to blend is straight forward, e.g. a straight horizon with no object (such as trees) sticking out into the sky, you can just use a white paint brush to paint straight on the layer mask.

In this instance, pay particular attention to the transition. Make sure you go through the transitional zone several times with the brush set to a lower opacity. This is to ensure the image is blended in naturally.

exposure blending without luminosity mask

This image was created with three exposure. The image exposed for the sky was blended in with free hand blending. This was feasible because the horizon was relatively straight and simple.

Better Image Quality

Another reason I prefer blending over HDR software is the image quality.

Although most HDR software today is better than before, the inevitable halo effect and image noise are still prevalent. Take a look at this example.

3 exposures (-2, 0, +2) merged into HDR in Lightroom with auto tone enabled. Note the halo along the edge and the subtle noise in the sky.

hdr created with exposure blending using luminosity mask

HDR created using blending with luminosity mask. The same multiple exposures, but only -2 and 0 were used. Compared the edge and the sky with the image above.

When Do I Use HDR Software?

I suppose that's the ultimate question for blenders (photographer who does blending - I made it up myself!)

I use HDR software when I find it difficult to blend exposures together. It serves as a backup in my arsenal, an escape route for me to get out of tricky situation.

You might be wondering: 

What images are there that can be challenging to blend? Check this out.

difficult exposure blending
difficult exposure blending
difficult exposure blending

This was the ONE example that I would never forget. The haze in the images was the major challenge. I couldn't get any luminosity mask that fits the selection I needed. In the end, I merge the images using Photomatix Pro and did further post-processing in Photoshop.

Sure, there is dehaze in Lightroom. But this was back in 2012 when I didn't have that luxury.

These days, I use Lightroom or Photoshop to merge multiple exposures into HDR. The file is then saved as TIFF without further slider adjustments within the Merge Into HDR panel. I do all my post-processing later on in Photoshop and Lightroom.

​I only use HDR software when I want a quick result, or a preview of what I can achieve with exposure blending. Personally, I feel blending is the best way forward to create HDR images that is clean and natural.

Take Home Message​

​Both HDR software and blending with luminosity mask can produce natural looking HDR images. In my personal opinion, I think photographers who enjoy creating HDR should know how both techniques work.

Learning a different technique adds to your arsenal of image post-processing skills. It bails you out when you're stuck (or get lazy!)​

Have you guessed which image is post-processed using HDR software and which is blended using luminosity mask?

Leave your answer in the comment! 🙂

  • rb763

    Great article. I also use HDR software when I want quick and dirty results but never completely satisfied. I’m trying to learn Luminosity Masking but my biggest issue is that I’ve been using PS and LR for so long I have fallen into habits of doing things my way which generally means painting or blending in adjustment layer masks.

    • Thanks 🙂 It does take a while to get use to the luminosity mask workflow. If you’re already painting or blending in adjustment layer masks, you just need to swap in an extra step of selecting a luminosity mask before painting it. Let me know if I can help in any way =)