Absolute Beginner's Guide to Digital Photography

Layer Masks: Attaching a Mask to a Layer

A layer mask is a mask attached to a layer. Layer masks are useful because each

mask only affects what is on the layer; the rest of the image is untouched. Two types

of layer masks are useful to photographers:

■ Image layer masks. A layer mask can make part of an image on its layer

invisible: Wherever the layer mask has full density (black), the image is hid-

den; and wherever the layer mask is transparent, the image is visible. A par-

tially erased mask makes the layer’s image partially visible. Outlining an

object is a common use for an image layer mask. By painting the mask black

around the object, you’ll make the layer around the object disappear.

To create a layer mask, choose Layer, Add Layer Mask, Reveal All. As a result

of choosing Reveal All, a transparent mask is created. When you paint black

onto the mask, that part of the image becomes invisible. This is a forgiving

procedure; if you make an error while painting, you can erase and repaint.

■ Adjustment layer masks. Creating an adjustment layer creates a transpar-

ent mask in the Channels palette. Whenever the adjustment layer is active in

252 ABSOLUTE BEGINNER’S GUIDE TODIGITAL PHOTOGRAPHY

FIGURE 16.16

Clipping paths

are used to cre-

ate unusual

shaped graph-

ics. You are not

limited to rec-

tangles or

squares.

The Purpose of Clipping Paths

Another valuable use for paths is as a clipping path (see Figure 16.16). A clipping

path is a mask. When an image that contains a clipping path is exported to another

software program such as Adobe Illustrator, the portion of the image outside the

clipping path is cropped; it is invisible (transparent) in the other program. For exam-

ple, if you create a clipping path around one person in a group photograph and

then export the image to Adobe Illustrator, only the clipped person is visible.