The Lightroom Select Subject mask tool and how it works

You’ll have noticed that Lightroom’s masking tools have had a major overhaul. The old Adjustment Brush, Linear Gradient and Radial Gradient tools are still there, but they’ve been joined by new Lightroom Select Subject and Select Sky AI masking tools, plus Color Range, Luminance Range and Depth range tools.

That’s not the end of it. These masks can be combined, ‘intersected’, added and subtracted, making Lightroom’s masking tools a lot more powerful than they were before.

The masking tools have now been consolidated under a single button, but this is not a simplification of the controls. This button reveals a new masking panel with all these options, and a new Masks sub-panel reveals the full range of controls available.

There’s a lot to explore here – too much for a single walkthrough. So this time I’ll look at the Select Subject tool, how well it works and what you can do with it. Adobe has been pushing its Sensei AI technologies for some time now and is this the time when it really starts to come good?

Step 01: The Add New Mask Panel

The Add New Mask panel is displayed with a single Mask button at the top of the tools panel in Develop mode. This opens a panel where you see all the masking options.

In this image I want my main subject, the gentleman on the vintage motorcycle, to stand out better. So rather than using the Adjustment Brush and Auto Mask to select him manually, I’m going to use the new AI-powered Lightroom Select Subject mask option.

Step 02: Select Subject and adjust

So does this bit of AI magic actually work? Absolutely! I’ve tried Adobe’s new wonder-tool on many different images, and it has an uncanny ability to work out (correctly) what the subject is and mask it really well. Even if it doesn’t do it perfectly, it’s usually close enough. You CAN use the other tools to improve the mask but mostly I don’t bother.

Here, it’s selected both the motorcycle and its rider, plus a sign by the front wheel and a bystander behind – I don’t mind either of those ‘extras’ too much. It’s missed a section of the front mudguard, but rather than trying to fix that, I’m going to press on with my adjustments and see if it matters.

You’ll see the Masks panel is now selected and my new mask is shown here. I can click on it to show the mask as a red overlay. In the adjustments panel, I’ve increased the Exposure to brighten my subject and pulled back the Highlights so that the man’s white shirt sleeves aren’t blown out.

Step 03: Invert to select the background

So far so good – but as part of the vintage effect I’m trying to achieve I want to desaturate the background and warm up the white balance. There is no Select Background tool in Lightroom, but it doesn’t need one because there is a quick and simple workaround.

I just create a new Select Subject mask – of course, it’s exactly the same as the first – but then check the Invert box in the sidebar. Now it’s the rest of the scene that’s masked and NOT the subject.

This is one of my favorite masking tricks. Very often it’s easier to select an area and then invert the selection than it is to select the area you actually DO want.

Step 04: Add new masks as you need them

I haven’t quite finished with this image yet. After making those two sets of adjustments, I decided the image looked a bit flat and dark. My favorite trick for these situations is to create new new, elongated Radial Mask with an increased Exposure setting and position it carefully in the image where it will do most good.

Here, placing it just to the left of the motorcycle’s front wheel gave just the lighting and compositional effect I was looking for.

Step 05: Name your masks

Here’s one more tip. The more masks you add to an image the harder it becomes to remember what each one does. So it’s a good idea to name your masks as you make them. The screenshots in the previous steps all show named masks and it’s easy to do this – Just right-click a mask and choose the rename option.

How good is the Lightroom Select Subject mask tool?

I touched on this in the walkthrough, but I think it’s very good indeed. Even if it doesn’t look quite perfect when you first create it, I think it’s worth carrying on with your adjustments anyway because very often it doesn’t matter and you won’t notice. It’s the results that count, after all.

The Select Subject tool has the potential to dramatically speed up your Lightroom workflow, and while I’m not usually a fan of ‘automatic’ adjustments or AI hype, this time it really works.

This walkthrough has only shown one of Lightroom’s new masking options. There are many more, and they can also be combined in a number of different ways, so there’s a lot more to cover in future walkthroughs.

Read more:

• Lightroom Classic review
• Lightroom review
• Lightroom vs Lightroom Classic
• Lightroom tutorials