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!—Photoshop has a digital equivalent: layer masks.

By adding paint to a layer mask, you can hide the content of the layer that the mask is attached to, whether it’s a pixel-based image layer, a smart object, a shape layer, a fill layer or—in the case of adjustment layers—a color or lighting change.

Learning to use layer 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 3-30. (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.

Wanna be a rock star? A layer mask can make that happen.Left: Here you can see the original, boring, blue background, as well as the new, exciting, clamoring crowd.Right: In this Layers panel, you can see that the original background wasn’t deleted—it was just hidden with a mask. (To make the color of the guitarist and the crowd match a bit better, a photo filter adjustment layer—page 359—was added that uses the same mask.) Like layer thumbnails, a mask’s thumbnail is an exact miniature of your document.

Figure 3-30. Wanna be a rock star? ...

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