Masking by Luminance Values in Adobe Lightroom

There’s this thing out there called “luminance masking” that’s sort of confusing. It’s a great feature that can be found in a number of Adobe products and it really shouldn’t be ignored. If you’re into using localized adjustment tools and have had issues with separating what you’re attempting to adjust with surrounding objects and areas, this may be just your ticket to success.

The luminance mask is one of the “range” masks inside of Adobe Lightroom. By range, I mean the mask will only work within a specified range of whatever that mask is. It’s actually sort of tough to explain this one, but I’ll do the best I can.

Let’s say I apply a Graduated Filter to an entire image in Lightroom. Pertaining to that graduated filter, I push a few sliders around to change the look of what’s behind it. So now, as it stands, I have an image with a filter over it that makes the image look completely different.

Let’s also say that the image I’m working with has some bright areas in it as well as some darker areas. What if I wanted to have the Graduated Filter only affect the bright areas? Can I do that? Well, with the Luminance Mask feature I can. What the Luminance Mask has the ability to do is hide parts of a filter, based on the image’s luminance. So, if you had a picture that was black and white and some parts were really bright and some parts were really dark and you applied a filter (Graduated, Radial, Adjustment Brush) to the entire image, you could easily hide some parts of that filter and protect other parts, based solely on how bright or dark those areas are. It’s really a very helpful tool and it’s one that should be taken advantage of.

I hope I explained the idea behind this feature clearly above. If you still don’t completely understand the concept, please read on down below. I think it will all come together.

In today’s post, I’m going to apply a Graduated Filter to an image of a mountain range. The reason I chose the photo I’ll be using is because there is obvious separation between the mountains and the sky above it. I’ll apply the filter and then push some sliders around to darken the sky. After that, I’ll activate the Luminance Range Mask in an effort to mask out the mountains from the filter. I don’t want the mountains affected by the filter at all; I’ll adjust the range mask so that doesn’t happen. Finally, I’ll smooth out the mask by pushing another slider, which will have a profound effect.

Today’s Demo Photo

This is the photograph I’ll be using for this post.

Like I said, there’s good separation between the mountains and the sky. I suppose you could say there are differnt “luminance” values between those areas, which is what will help when using these tool I’m speaking of.

Applying the Graduated Filter

Since I’ve already written a nice post on how to use the Graduated Filter in Adobe Lightroom, I’ll just link to that below and go ahead and apply the filter. If you’d like to read about this topic, I encourage you to click through.

Beautifying an Image with the Graduated Filter in Adobe Lightroom

Okay, I’ve gone ahead and clicked the Graduated Filter icon in the right side of the Develop panel.

After that, I reduced the Exposure and Blacks values so they are -2.04 and -20 respectively. Here’s a screenshot of the sliders.

And here’s the output of the image as it stands.

Here’s the problem. While it doesn’t look like anything is wrong with this image, there is. the “darkness” of the filter I just added is covering up many of the stars and it’s also slightly reducing the illumination of the tops of the white mountains. Someone probably wouldn’t even notice this if they hadn’t seen the original version of this photo, but since we have, it’s too late. We know what it’s supposed to look like.

Activating the Luminance Range Mask

To correct this issue, I’m going to move down to the bottom are of the right panel and click the Range Mask drop-down box. When the box opens, I’ll select Luminance.

After I do that, two additional controls will appear in the form of sliders. These two sliders are labeled Range and Smoothness.

Okay, here’s the truth about these two sliders. They are going to need to be experimented with for you to get used to them. I’ll explain them below, but the results will still be unpredictable the first few times you use these things.

Think about the Range slider as a control for where you want the graduated filter effects to appear. As I stated up above, this slider can control which parts of this image the filter are applied to, so if I wanted the filter to affect only the bright areas, such as the stars and the white mountain tops, I can certainly make that happen. Of, if I wanted this filter to ignore the stars and white mountain tops, I can make that happen as well. All I need to do is push each of the small slider controls to the left or the right to find that sweet spot of what I’m after. In this case, I kept the left control where it originated at the 0 value and pushed the right control to the left until it had a value of 85.

The Smoothness slider does exactly what you think it should do. It smooths out the transition between the area the luminance mask is affecting and the area that mask isn’t affecting. The higher the Smoothness value, the smoother the transition. If I were to keep this slider all the way to the left so it had a very low value, the transition would be sharp and abrupt. Since I’m looking for something more realistic, I’ll push the slider to the right until is has a value of 65. That’s nice and smooth.

Now I’m looking at a much better result.

Here’s the final image, which is slightly more exciting than the original.

I just want to tell you that there are a zillion different uses for this range mask and tons of different possible results you might see. You really need to play around with this tool to get a gauge of what type of effect you can conjure up from it. What I showed you above is a good start.

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I hope I clearly explained how to use the Luminance Range Mask feature in Adobe Lightroom. If you have any questions regarding this post, please leave them in the comment section down below. Thanks for reading!