Photoshop CC: The Missing Manual

Layer Masks: Digital Masking Tape

Remember the last time you gave your walls a fresh coat of paint? You probably broke out a roll of masking tape and taped up the baseboards and molding so you wouldn’t get paint all over them. Sure, you could’ve have taken the baseboards off and put them back on once the paint had dried, but dadgum that’s a lot of work. Besides, masking tape covers everything just fine. Hiding and protecting is masking tape’s special purpose and—what luck!—you’ve got its digital equivalent right in Photoshop: layer masks.

By adding paint to a layer mask, you can hide the content of the layer it’s attached to, whether it’s a pixel-based Image layer, Smart Object, Shape layer, Fill layer or—in the case of Adjustment layers—a color or lighting change. Learning to use masks will keep you from having to erase parts of an image to produce the effect you want. Once you erase, there’s no going back, and if your hand isn’t steady enough to erase around detailed areas, you may accidentally erase bits you want to keep. So, for example, instead of deleting a background so you can swap it with another one, you can use a layer mask to hide it, as shown in Figure 4-29. (You’ll find all kinds of other uses for layer masks sprinkled throughout this book.) As long as you save the document as a PSD file, you can go back and edit the mask anytime.

Figure 4-29. Left: Wanna be a rock star? ...