Using the Select Subject Feature in Photoshop

Any experienced Photoshop artist knows that most of the grunt work involved in composting images lies in creating cutouts of the components you want to use. For years the only solution was painstakingly tracing an outline with the Pen Tool, with QuickMask as an alternative that allows you to paint selections. Photoshop CS3 introduced the revolutionary Quick Selection Tool, which allows you to drag over the area you want to automatically select its boundaries.

Now, Adobe has seemingly achieved the impossible with its new Select Subject command, unveiled with the January 2018 update to Photoshop CC. We put the tool through its paces to see just how well it performs in real-world situations.

Selecting a single subject

This photograph of President Trump may look a little waxy – and that’s because it isn’t the real president, but a model of him in Madame Tussaud’s waxwork museum in London. Choose Subject from the Select menu and, with no other effort on the part of the user, Mr. Trump is selected in one go. The tool has managed to capture him almost perfectly, with a few ragged edges that can easily be smoothed away with the Select and Mask dialog. Here, the original photo is shown on the left, with the automatic cutout on the right.

Selecting a pair of subjects

But what happens when you get more than one subject of interest in an image? No problem: Photoshop will capture them both simultaneously, in just a couple of seconds. Here, the waxworks are of British Prime Minister Theresa May and her Foreign Secretary, Boris Johnson. The fiddly, detailed background has caused a few minor issues, with bits of railing and masonry appearing in the selection; but it’s a remarkably good first capture, and again it’s a simple matter to tidy it up.

It’s not just people

It’s just conceivable that Adobe might be able to engineer intelligent technology that can recognize people—since most people do, ultimately, look like people, with the requisite number of arms and legs. But what if the subject of your photograph isn’t a person, but an object?

In this instance, we used a photograph of a vintage car shot against a fairly complex background. Once again, Subject was chosen from the Select menu.

The object result

And this is what Photoshop produced for us. It may not be a perfect cutout, but the program has certainly recognized the difference between the car and the background. It’s interesting to note that it has captured the shadow along with the car.

Refining the cutout

Using the Select and Mask dialog, it takes only a few minutes to sort out those ragged edges, producing a perfect cutout in a fraction of the time it would take to do the whole thing manually. If you wanted to take it further, of course, you could cut out the view through the windows as well.

Doing its best

Sometimes Photoshop has difficulty distinguishing exactly where the subject begins and ends, as with this photograph of a pangolin taken in a museum. It has captured the basic shape, but included part of the badger-like creature behind it, as well as the shadow around the feet—although you can understand why both of these elements confused the issue. Less understandable, perhaps, is why Photoshop included the background between the claws in its selection.

Stay focused

Part of the way Photoshop decides what’s the subject and what’s merely background is by looking at which elements of the image are in focus, since it assumes that the photographer is more likely to focus on the area of interest.

So in this image of a plane, the nose and cockpit have been correctly captured, and it has made a fair stab at the front wheel. But the back of the plane, which was out of focus due to the close-up nature of the photograph, has been omitted entirely.

Conclusion

As with most automated systems, the Select Subject command gets you about 90% of the way there, and if you’re lucky, it will get you a lot close than that. You can’t expect perfection from a technology as radical as this. But it’s a command that will undoubtably become most users’ go-to solution for separating a subject from the background. And it’s sure to save a lot of time for illustrators and designers in all disciplines.

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Posted on: January 24, 2018

Steve Caplin

Steve is a freelance writer, artist and designer, and the author of over a dozen books, including the popular How to Cheat in Photoshop series and the Amazon #1 best-seller Dad Stuff. His training videos can be seen on lynda.com, Retouch Pro and elsewhere.

7 Comments on Using the Select Subject Feature in Photoshop

  1. Is it simply a Menu command or is there a procedure? A little technical description of its use rather than a series of its effects would have been more helpful.

  2. At some point I’d expect AI to help identify all the car vs. non-car parts (e.g., from looking at a million examples of similar cars) and get close to 95% every time.

    • I think you might be expecting too much. Can Photoshop distinguish between a tire and its shadow? If so how?

      • Yes, this is expecting too much of Photoshop now but CJ is correctly imagining where this is going. We already have photogrammetry in other apps. As 3D photography becomes more popular (as you already see it in augmented reality apps on your phone), it will be easier for an app like Photoshop to better assess the physical elements in scene, distinguishing that tire from its shadow.

        Keep an eye on SIGGRAPH technical submissions. Most recent whiz-bang Photoshop features have been hinted there years in advance.

  3. I’m running Photoshop CC 2018 but can’t see the Subject option in the Select menu. I’ve checked for updates but there are none.
    Confused, Portsmouth

    • It should appear directly beneath Color Range and Focus Area in Photoshop’s Select menu. If it’s not there, you must have not updated your copy of Photoshop CC 2018!

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