Photoshop Basics: Using Layer Mask

Using Layer Masks in Photoshop
by Karyn Lewis

There are a ton of things in Photoshop that can make your design or illustration life easier. One of the most powerful tools is Layer Masks. I worked for a few years without this handy feature, but once I figured it out, I’ve pretty much used it in every piece of art I do. So just what is layer mask? Basically, you use layer mask when you want to hide part of your image.

Why on earth would you want to do that, you might ask. Here’s one example. I’ve got a picture here of a model from my Zazzle store wearing one of my Saint Patrick’s Day designs. He’s standing against a plain white background.

I want to use this guy on a banner logo, and I need him to be standing in front of a transparent background. Basically, I want to erase the white. So why not just use the eraser? Well, I could, but if I make a mistake, I have to live with it. Bottom line: If I erase something, it’s gone for good. However, if I use layer mask instead, I’m just hiding the white area of the picture from view, not deleting it. In a more complicated work, this is really handy because it means you can make changes to your pictures without ever losing the original image.

So how does the layer mask work? It’s super simple. In this case, we’ll do it the quickest and easiest way. You’ll need two layers — the first one is your plain background layer and on top of that should be the image you’re working on. In this case, that’s my studly model in his St. Paddy’s shirt.

Now comes the idiot-proof easy part. Go to your tool palette and select the Magic Wand Tool. Place it anywhere over the white area in the picture.

Click on it and you should see a line of ‘marching ants’ surrounding the white area of your photo.

Invert your selection by going to menu option: Select: Inverse (or click Shift+Ctrl+I).

At the bottom of your layer’s tray, you’ll see a little row of buttons. The one that looks like a little square with a circle inside it is your layer mask button.

Click on it, and viola! You have just created a layer mask.

Now the white area is transparent, and the green background shows through. Let’s look at our layer palette again so you can see what the layer mask is doing.

Do you see the little black and white silhouette next to your photo in your layers palette? That’s your layer mask thumbnail. You can see clearly that what is white is visible, and what is black is transparent. While your photo layer is active (in this case, it’s Layer 1), click on your mask layer thumbnail so that it’s selected. That step is important. Don’t forget it! Now, using black and white brushes, you can draw on top of the picture and you can hide or reveal bits of the picture. For example:

Using a basic round brush set to the color black and at 100% opacity and flow, I drew a big diagonal stripe down the picture. And what happened? It ‘erased’ my photo where I drew. But that’s the beauty of using masks. I didn’t erase the photo at all. I just masked out what I didn’t want showing.

To undo what I did, just switch your brush color to white and paint over the masked parts of the photo, and they’ll magically reappear. In the next photo, you can see the result and compare it to the layer mask thumbnail. Remember, black hides your image and white reveals it.

Now that I know how to use layer masks, I can take my transparent model and place him in my banner logo without worrying about erasing that ugly white background.

In future tutorials I’ll show you other cool uses for masks. Hope this helps!