Layer Masks Simplified. By Chip Phillips

It seems that one of the most misunderstood, and most powerful, options in Photoshop is the use of layers, and more specifically, layer masks. In my opinion, this is the single most powerful tool in Photoshop. When I first learned about how to use layers and layer masks, it brought my photography to a whole new level. It is sometimes surprising to me how many people have been using Photoshop for years, but don’t know what a layer mask is, or how to use one. It is also one of the more difficult things to explain in my teaching. But, once my students grasp the concept, it becomes a powerful tool for them, and they never look back. I will try to simplify the concept in this post.

What is a layer?

If you don’t already use layers in Photoshop, you should. Most of the adjustments that you make to an image are available as “adjustment layers”.

Every adjustment that you make to an image via an adjustment layer is non-destructive, meaning that the original “background layer” stays in tact. You can always go back to your original background layer if you don’t like the adjustment you make, or at a later time.

Every adjustment layer comes with its own mask as well:

What is a Mask?

Imagine a scratch ticket. It comes with that grey stuff over the numbers. When scratched with a coin, the underneath part is revealed. The concept of masks in Photoshop is very similar. When the mask is filled with black:

the adjustment is completely hidden. Just like the scratch ticket that hasn’t been scratched yet.

When it is filled with white, like the previous example, the adjustment is completely visible. Just like the scratch ticket that has been completely scratched until all of the grey is gone.

A basic concept to know and memorize before you start using masks is: white reveals and black conceals. The layer mask that comes with adjustment layers is white by default. So, the adjustment that you make via an adjustment layer is completely showing. You can hide the adjustment by switching your foreground color to black (if it isn’t already). Do this by clicking on the little double arrow at the bottom of the tools palette to place the black square on top:

Now, select “alt-backspace” PC, or “option-delete” (I think), Mac. This fills the layer mask with black, completely hiding the adjustment.

Here is where the magic occurs. With the layer mask filled with black, click on the little double arrow again at the bottom of the tools palette so that the foreground color is back to white.Next, select the brush tool:

Now, with the opacity set on the low side at first:

and a soft brush, paint in your adjustment to exactly where you want it. You can increase the opacity or decrease it as you please. Also, when you are finished, you can refine this “painted adjustment” further by adjusting the opacity in the layers palette:

As you can see, this offers the photographer quite a bit of control. Adjustments are no longer global, and the creativity possible is endless.

A layer mask can be added to just about any layer (if one isn’t already there) by simply clicking on the little layer icon at the bottom of the layers palette:

You can also “alt-click” (option-click Mac) and the layer mask will appear filled with black, hiding the adjustment completely. Now just paint with white.

Just remember: white reveals and black conceals. Also, it is important that the mask is active when you go to apply white paint. Make sure the mask is outlined in the layer palette. In this example it isn’t outlined:

In this example it is:Just click on the mask to make it active.

I use layers and layer masks extensively in my own processing. The concept might seem a bit mysterious at first, but it is really simple once you have a basic understanding.

Hopefully, if you don’t already, you will start using adjustment layers, and layer masks in your own processing.