Adobe Illustrator CS5 One-on-One

Working with Opacity Masks

If you’ve ever used Photoshop, you may know that you can erase

temporary holes into a layer using a layer mask. Illustrator offers

something similar, but because it’s not restricted to a layer, it goes

by a different name: opacity mask. In many ways, an opacity mask

is like a path in a compound shape set to Subtract or Intersect, carv-

ing a hole or containing other paths. The differences between those

modes and an opacity mask are that the latter works with paths

that include all varieties of fi lls and strokes (whereas all paths in a

compound shape must subscribe to a single set of attributes); it can

convey fades and levels of translucency; and you can apply it to a

layer, group, text block, blend, gradient mesh—in short, to anything.

In return for such fl exibility, the opacity mask demands that you

come to terms with its unusual ways. Which is why I’ve organized

this exercise differently from the others. I’ll start things off with a

few steps that—while they don’t get us any nearer to our ultimate

goal—demonstrate how the opacity mask works. Then you’ll use

this knowledge to clip away the jacket ele-

ments along Sam’s head, clip away Sam’s ex-

cess pant legs, and create a fading piano. As a

bonus, I’ll show you a great use for blending

between groups.

1.

Open your last-saved fi le. Con-

tinue working with the fi le that

you saved at the end of the pre-