Adobe Photoshop CS5 One-on-One

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CREATIng AnD APPLyIng MASkS

If YOu’Re lIKe most Photoshop users,

you’ve at least heard of masks. Or perhaps you’ve
heard them called mattes or alpha channels or
any of a half dozen other terms. But whatever
you call them, their purpose is the same: to
block out one portion of an image and reveal
another, as illustrated in Figure 10-1.

Essentially, what I did in Figure 10-1 was select
the woman’s face and move it into the mirror.
But I never could have achieved such an accu-
rate selection if I had relied exclusively on the
lasso, wand, and pen tools. Masking lets you
use the colors and luminosity values inherent in
the image to define a selection outline. In effect,
you use the image to select itself. You can do
this in a myriad of ways in Photoshop. Mask-
ing takes some getting used to, but once you
do, no selection tool is as accurate or efficient.

Seeing through Photoshop’s Eyes

In real life, we have a natural sense of an object’s
boundaries. You may not be able to make out
an individual flower in a crowded garden from a
distance, but get close enough, and you can trace
the exact border in your mind (see Figure 10-2,
page 339). So why does Photoshop have such a hard
time with it? Why can’t you just say, “Choose
the flower,” instead of painstakingly isolating
every single leaf, stem, and petal?

The source imageThe destination

The maskThe composite

Figure 10-1.