How to Make Precise Selections in Lightroom CC

The exposure brush in both Lightroom Classic CC and Lightroom CC is extremely powerful.  Many of the capabilities found in the very precise Select and Mask tool in Photoshop are found in this brush.  The great news is that you don't have to mess with a lot of sliders or different options to get a near perfect selection.  I've found the brush to be one of my most used tools in Lightroom, so I'll be teaching a few simple tricks to get the most out of your images.

Note: The main difference between Lightroom Classic CC and Lightroom CC (aside from the somewhat confusing name) is that Lightroom CC doesn't have the luminosity or color sliders (yet).  All of my demonstrations will be from LR Classic but aside from these sliders, all the concepts are the exact same in LR CC.

The first thing you'll need to do in order to get the most of your brushing is to turn on the overlay mask.  Without this, you'll just be making your best guess as to what you are doing with your exposure brush and that's really hard to do.  So press the letter “O” on your keyboard while your brush is selected and you'll turn on a red overlay.  If you haven't actually started brushing anywhere, you won't see anything, but once you brush something on your image, you'll see this overlay appear.  Press the letter “O” (for overlay) to toggle this on and off.


In the photo above, you'll see a classic example of over-brushing.  This is using the brush without the Auto Mask checked.  What's happening is the brush is applied to everything on the image, including the parts where you don't want or need it.  I wasn't able to get a precise selection of the sky and have included a lot of the hill in the background and almost all of the tree in the foreground.

When you are just getting started with photography you may not think this is a big deal.  There won't be much detail in those parts of the image any, right?  So a little over-brushing isn't going to bother anyone.

Check out this photo of the final image with some areas over-brushed.  You'll see just how much detail is going to be affected and lost due to not controlling the brush.

Instead of looking like a weathered, old tree, it now looks like it was in a forest fire.

There is actually quite a bit of coloration and frost detail in the dead tree that will come out almost pure black if we don't clean up our brush strokes.  The trees on the hill in the background also lose their detail and will come out almost completely black.  There was some very cool fog flowing through this scene that caught the morning sunlight and gave that hill a gentle glow.  It felt like the sunrise was spilling over the edge, like an overflowing reservoir.  Without careful masking, I'd lose all that detail and in turn, lose the feel of this crisp winter morning in the mountains.

Using the Auto Mask

By checking the Auto Mask option on your exposure brush (located at the very bottom of the brush panel), you'll enable a powerhouse of calculations that will almost effortlessly create a precise mask.

Auto Mask works like this: the first group of pixels where you click your brush will be set at the base of luminosity and color.  When you start to move the brush around, everything that is similar in brightness and color will be masked automatically.  This works extremely well when you have something like a dark tree against a bright sky.  It is also extremely powerful at masking out those teeny tiny branches against a sky.

Remember: the first place you click, the place where you have your brush centered, will be the deciding factor in your Auto Mask.  If you place it on a bright area, like the sky, then all bright pixels will be masked as you brush over your image.  If you place it on a dark area, like a tree, then all the tree (and tree-like objects of similar color or brightness) will be masked.

See the example below of an Auto Mask brush selection:


We've done a great job at just masking the sky and haven't affected our tree or it's branches.  This will give us a clean mask to work with to adjust the exposure on both of these separately.

Next up, we'll see how well the Auto Mask worked for the trees on the hillside.


As you can see, we've got some great selections between the sky and the trees.  However, one of the downfalls here is that the very tops of the trees are too similar in luminosity to the sky because of all the light bleeding through the fine branches.  You can see that the tops of the trees are red in color, meaning they are part of that selection.  Don't fret, we can clean this up even further.

Using the Erase Brush

Now we'll get into some capabilities of the exposure brush that are really going to blow your mind.  With your brush selected, hold down Alt (PC) or Option (Mac) to enable the Erase Brush.  This will erase the mask you've just applied.  By enabling the Auto Mask on the Erase Brush, we'll be able to refine the mask even more.

The Erase Brush works in the exact same way as the regular brush: whatever pixels are in the exact center of the brush will be the base pixels that Lightroom will apply (or erase, in this case) this mask to.

Here is a little technique that I've learned that works great to clean up a little bit of mask spillage.

  1. Zoom into your image to 1:1.
  2. Make sure your Flow and Density are set to 100.
  3. (While holding down Alt/Option) Make your brush big.  Like, really big, so it takes up half the screen.
  4. While still holding down Alt/Option (you can't let it go or you'll go back to your Apply Brush) center the brush on the very tops of the trees.
  5. Click once.

Boom! You'll see that the tops of all your trees in your brush radius have now been cleaned up and de-masked.  Compare this screenshot to the previous one to see how we've been able to clean up our selection of the sky and remove the trees from it.  Repeat this as necessary so all the tree tops are cleaned up.


If you follow these steps and, Oh no! A big chunk your sky is now de-masked! Don't worry.  Just hit the “undo” button to restore your previous mask and try again.  What happened is that the center of your brush wasn't on part of a tree, but rather it was on part of the sky.  Re-center your brush and give it another go.

Using the Range Mask

The Range Mask is a fairly new tool, only available in Lightroom Classic CC (Lightroom CCC? Lightroom Triple C?  Sounds like a fancy horse race.) for now.  There are two options in your range mask: Luminance and Color.  What your Auto Mask does for you, Range Mask allows you to have more control over what is masked and what isn't.

In this example, we see how the Luminance Range Mask allows us to de-mask the trees in the hillside by adjusting the range closer to 100.

Here I've got the range set to 60/100 and it has de-masked much of the trees.  The tops are still selected, which you can clean up with your Auto Mask Erase Brush as we talked about earlier.


Here is another example of the Luminosity Range Mask at work.  You can see that it's done a pretty decent job at getting out the tree and branches but the ends of most of the branches are still masked.  You can clean these up with your Auto Maks Erase Brush as show in the second image.


Shortcomings of the Range Masks

As good as technology is, it isn't perfect and won't work in every case.

In this image of a sunrise at Lake Powell, I want to show you where Range Masks still have a hard time.  They seem to fall short where there is too gradual of a transition between color or luminosity.

Here is the overlay of a manual brush:


Here I tried to adjust the mask with the Luminance Range Mask.


As you can see, the mask never quite gets cleaned up.  Lightroom is having a hard time trying to figure out what is sky and what is rock.  No matter how much I adjust this (using both Luminosity and Color options), I still cannot separate the mask between sky and rock.  I mean, you and I can clearly see the difference, right?  Lousy Lightroom probably can't tell me why kids love the taste of Cinnamon Toast Crunch either.

However, the Auto Mask worked amazingly well in this scene.  You can see that my Range Mask is off, my Auto Mask is on, and vioala.  A crisp mask between the sky and the rocks.


More tips and tricks

A few more things to mention with the exposure brush to get you on your way.

  • When you are using Auto Mask, always make sure your overlay is enabled.  This will allow you to see where your mask is.
  • You can brush over an area several times that isn't being included in your mask that should be.  This happens a lot with clouds; there is too much difference between them and the sky and Lightroom will think you don't want them included.  Brushing over these areas with a few strokes will tell Lightroom to include these kinds of pixels in this mask.
  • Give your Erase Brush a broad feather (the outer circle is far away from the inner circle) and use the feathered part of the brush to make your mask erases if doing it manually.  You'll end up with a smoother, more feathered masked that looks more natural.
    • You'll also avoid mistakingly erasing huge chunks of your mask by accident.
  • The darkness of the red overlay mask will indicate how much your exposure sliders will affect that area.  The darker the red, the heavier the changes will be.
  • Auto Mask works great in areas with high luminosity or color contrast: trees against sky, red against green, dark against bright.

What tricks have you learned with the exposure brush?  Tell us in the comments!

5 thoughts on “How to Make Precise Selections in Lightroom CC”

  1. Nice article Kirk. I will have to try some of your refinement tips. I thought I’d mention that often I make my mask color green rather than red as it shows up better for me. As you point out, the “O” key will toggle the mask off and on and Shift + “O” will cycle the mask color. Helpful when the mask might blend in too much with the background colors in your image.

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