As you can see in Figure 10-17, this image by photographer Stas
Perov, from the Fotolia.com image library, presents a couple of sig-
nificant masking challenges. First, we’re working with that quint-
essential masking bugaboo, wild hair. Added to that, we have very
low-color information to work with, given the predominance of
low-saturation blues in the hair, the background, and the dress.
Figure 10-17.
We’ll begin this masking odyssey with the Calculations command,
one of the more sophisticated, mathematical, not-exactly-intuitive
tools in all of Photoshop. Calculations compares the information
in two different color channels, lets you designate a blend mode,
and comes up with a mathematical extrapolation that it expresses
as an alpha channel. You can then use that channel as the basis for
a mask. It sounds daunting, but stick with me and you’ll see how
useful it can be.
- Open the notorious image. Navigate to the Lesson
10 folder inside Lesson Files-PsCS5 1on1 and open the
aforementioned file, Hair assault.jpg.
Masking with the Calculations Command 351