How to Composite Your Photos Seamlessly

November 6, 2014

By Damian Battinelli

Compositing can help you create an image you may not have been able to do in camera and it’s a skill I highly recommend mastering. Compositing is all about using layer masks and after learning this method you’ll rarely, if ever, use Photoshop’s Eraser Tool again.

The Eraser Tool is destructive and destroys pixels without being able to save your changes and fix them later. Think of a layer mask, which is nondestructive, as a magical cloak you can come back to and reveal what’s underneath while working on your Photoshop file weeks, months or years later.

My composites, which involve people, are done by photographing the subject separately from the background—usually in a studio setting, but not necessarily so. The key is making sure the light on the subject is similar to the intended background, so that both look like they belong in the same environment. After opening the image in Photoshop, I remove the subject by using the Quick Selection Tool and adding a layer mask. With this technique, I can remove the subject with precision and accuracy using my Wacom tablet. I can easily clean up the edges of the subject, making it seem like they were in the shot to begin with.

Take note that you can’t add a layer mask to your initial background layer and have it work properly unless you make a copy. Make a copy of your background layer by selecting it and pressing COMMAND+J. This new layer is the one you’ll be using. Next, create a new layer, fill it with a neon green color, and place it in between the background layer and your background copy.

This will help you see what you’re doing and will make more sense as you continue. Use the Quick Selection Tool to select the subject by clicking and dragging within and along the edges of the subject.

Make sure not to select too much of the background, and keep your brush size small. 

To deselect an area, hold down ALT/OPTION, and you’ll notice the tool now shows a negative symbol, now you can drag it over the unwanted area.

While your selection is made, click on the icon at the bottom of your layers panel that looks like a square with a white circle in it.

When you add a layer mask you’ll notice a black rectangle with a white silhouette appears next to the layer thumbnail in your layers panel. 

A layer mask is used by brushing either white or black over the mask using the Brush Tool. You must select the layer mask, or you’ll be brushing on your image and not the mask! Keep your brush to a size and hardness that matches the edge you’re trying to follow, and start cleaning up your edges. Black hides and white reveals, so you’ll always be able to go back and forth—it’s all still there. In other words, it may seem like you’re erasing, but
in fact you’re only hiding.

As you’re working you’ll see the green layer becoming visible. 

This is how you’ll be able to see what you’re doing. Now that you have your subject “removed” from the background, you can drag and drop it onto the new background. 

You’ll also be able to save your image, which contains your mask, and revert back to it at a later time when you’re satisfied and flatten your image.

Keep playing around with this technique; as you become more familiar with it, you’ll be able to get elaborate, adding in other elements like skies. It’s also a lot of fun!

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