When you see a flower, you knowprecisely where it begins as well aswhere it ends.Well, the truth is, you can, provided you know how to speak Photo-
shop’s language. A long conversation may be required, and you
might have some misunderstandings along the way. But with a little
time, a bit more patience, and a lot of experience, you’ll learn to
translate your vision of the world into something that Photoshop
can recognize as well.
As you may recall from Lesson 6 (see “The Nature of Channels,”
page 196), Photoshop never actually looks at the full-color image.
Assuming that you’re working in the RGB mode, the program sees
three independent grayscale versions of the image, one for each color
channel. A mask is just another kind of channel, one in which white
pixels are selected and black pixels are not. So if any one of those
channels contains a very light foreground subject against a very dark
background, you’ve got yourself a ready-made mask.
More likely, however, each channel contains some amount of high-
lights, some amount of shadows, and lots of midtones in between.
But that’s okay because the strengths of one channel can compen-
sate for the weaknesses of another. Take the sunflower, for example.
If you inspect the individual color channels, you’ll find that each
highlights a different portion of the image.
Figure 10-2.Seeing through Photoshop’s Eyes 339