How to make a layer mask from a selection

Turn a selection into a layer mask to replace a photo background.

Published January 28, 2025

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00:01

Introduction

If there's one key - to getting better at Photoshop, it's layer masking.

So we've put together - this short tutorial series to help you with layer masking basics.

I'm Jan Kabili from Adobe's learn team, and I'm excited to be your guide - for this short course.

In this tutorial, I'll show you - the fastest way to make a layer mask by starting with an automatic selection - and turning it into a layer mask.

Along the way, you'll learn the best way - to replace a photo background as we take an image from this to this.

You don't need a lot of experience - with Photoshop before you take this course, but you'll get the most out of it if you're familiar with the basics - of layers and selections.

In the meantime, let's get started - making a layer mask from a selection.

00:52

Planning a non-destructive background replacement

The image we'll be working with - has two layers, this photo of a photographer - in front of a fence on the top layer and this blurred cityscape - on the bottom layer that we're going to use - to replace the fence and give the photographer - a brand-new background.

Now you might think that the best way - to replace the fence would be to erase it.

But that would permanently alter the image, - which would make it difficult to change our minds if we wanted to take the image - in a different direction later.

So instead of erasing the fence permanently, - we'll use a layer mask to just hide the fence temporarily.

How are we going to make that layer mask?

In this tutorial, - we'll use the simplest way to create a layer mask, which is to make an automatic selection, - and then turn that selection into a mask.

We'll start here in the Layers panel - and make sure that the top layer, the Photographer layer, is highlighted.

Because this is the layer - to which we want to add a layer mask.

Then we'll make a selection - of the photographer,

01:55

Selecting the main subject with select subject

we could use any selection method, - but Select Subject is a good choice because it's an effortless automatic method.

And it usually does a good job - when there's a dominant subject to select, like the photographer in this image.

So we'll go up to the Select menu and choose Subject.

And that applies - the Select Subject command.

Now if you take a look at the edge - of the photographer, you can see these moving dotted lines, - which are called the marching ants.

And they're showing us - that there's a pretty good selection all around the photographer, - and even in this small area above her arm where the fence is showing through.

So we're done making the selection.

Now we're going to tell Photoshop - to automatically turn the selection

02:45

Converting a selection into a layer mask

into a layer mask with just one click.

To do that, - we'll go to the bottom of the Layers panel and click this icon that looks like a circle - inside of a rectangle.

This is the Add Layer Mask button.

That caused Photoshop - to make a layer mask, which you can see here - in this new thumbnail that's on the Photographer layer.

The next step is optional.

But if you want to get a better view - of this layer mask, you can hold the Option or Alt key - and click on that layer mask thumbnail.

And that will show the layer mask - here in the Document window.

In here you can really see - that on the mask, the area that was selected is white, and the area - that was not selected is black Photoshop added the black - to the mask automatically, because a selection was active - when the layer mask was created.

And that saved you time and effort of manually adding black and white - to the mask by brushing or applying a gradient - to the mask or making a selection and filling it.

03:53

Understanding mask behavior and final result

Some of which we'll do - in other tutorials in this series.

Now it's important to remember - that black on a layer mask hides content on the mask layer, and white on a layer mask - shows content on the mask layer.

So let's go back to the regular view - to see what that means for this image.

Again, I'll Option or Alt click - on the layer mask thumbnail.

As you can see, the black part - of the layer mask is hiding the area - all around the photographer so the cityscape can show through and the white part of the layer mask - is showing the photographer.

And that's exactly the result we wanted.

So we're pretty much done.

But that was a lot.

So let's recap the top four things - I'd like you to remember from this tutorial.

Number one, a quick way - to make a layer mask is to make an automatic selection - and then convert that selection into a mask.

Number two, this not only makes - a new layer mask, it also populates the mask - with black and white, black where there was no selection and white where there was a selection.

Number three, black on a layer mask - hides content on the masked layer and white on a layer mask - shows content on the masked layer.

And finally, the result - of this quick technique is a non-destructive, reversible layer mask - that you can change at any time.

And it gives you a great way - to replace the background of an image. -

What you learned

How to automatically select a subject Select the main subject on a layer automatically using Select > Subject.

How to turn a selection into a layer mask You can turn any selection into a layer mask by creating a layer mask while the selection is active. When you make a layer mask from a selection, Photoshop automatically adds black to the layer mask where there was no selection, and Photoshop leaves the area where there was a selection white.

How to replace a background nondestructively One use for creating a layer mask from a selection is to replace a background. The black that Photoshop adds to the layer mask hides the area around the selection, without deleting that area permanently. This causes layers below to show through and appear as a new background for the subject.

Instructor: Jan Kabili
Adobe Stock Contributors: Newroadboy; Bnenin

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