Photoshop Tips – Intro to Layer Masks

The ability to use Layer Masks is one of the more powerful features available in Photoshop. Yet, many beginning Photoshop users find it difficult to understand the purpose of masks and how to use them.

Once you understand what masks are and how they work, you’ll have a much easier time blending together layers, filters and effects, and you’ll be able to work with your images non-destructively.

First, let’s look at what a Layer Mask is: it’s an editable mask that is attached to your layers that controls the transparency of the layer. They contain only black and white tones, no color information. The white areas of your mask reveal your layer’s contents; the black areas conceal your layer’s contents.

Think of placing a sheet of transparency paper over a printed photo. Because the transparency paper is clear, you’re able to see your photo perfectly. Now, start painting over your transparency sheet with black paint. The areas with black paint conceal your photo.

Layer Masks work in much the same way. By default, a Layer Mask is white which is like the transparency sheet. As you add black to your Layer Mask, you will start concealing your layer’s contents.

Layer Masks take things a step further than the transparency paper, however. When you add black to the Layer Mask, you are hiding that portion of the layer and that portion becomes transparent, exposing the other layers beneath.

Allow me to illustrate this. Check out the image to the right. In my Photoshop file I have two layers: the bottom layer is an image of Leopard’s default wallpaper. The top layer is Tiger’s default wallpaper. I’ve added a Layer Mask to the Tiger wallpaper layer and created a black and white gradient across the image. Where the Layer Mask is white you see Tiger’s wallpaper; where it’s black you see Leopard’s wallpaper. Where the Layer Mask is gray you only have partial transparency; that’s how we’re able to get a smooth transition between the two layers. Keep that in mind as you continue to work with Layer Masks is that you don’t have to use only pure white and pure black.

We can view the actual Layer Mask by pressing Alt/Option and clicking directly on the Layer Mask thumbnail. As you can see we have a simple gradient, but as a Layer Mask this can give us some very cool effects.

To add a Layer Mask to your layer, simply click the Layer Mask icon at the bottom of the layers palette (Alt/Option + Click the icon to add a black layer mask) or you can go to the Layer menu and choose Layer Mask > Reveal All (or Hide All to add a black layer mask).

After the Layer Mask has been added, make sure its thumbnail is selected in the layers palette and use the editing tools as you normally would to manipulate your image. You can switch to your original layer whenever you’d like by clicking on its thumbnail in the layers palette. This enables you to edit the contents of your layer separately from your Layer Mask. Just click on the Layer Mask thumbnail again to switch back to it.

While you’re working on your image, you may want to see what your image looks like without the Layer Mask applied at all. To hide only the Layer Mask, simply Shift+Click on the Layer Mask thumbnail in the layer’s palette. A red X will appear over the mask and you will be able to see all the contents of your layer. Shift+Click on the Layer Mask thumbnail again to reactivate it.

One of the main benefits of using Layer Masks is that you are doing non-destructive edits. At any time you can hide or delete your Layer Mask and your original image has remained untouched.

As you can see, Layer Masks are a very powerful and integral part of Photoshop. They help make your Photoshop work faster and easier and meanwhile make it easier to return your image to its original state by working non-destructively.