CHAPTER 17 THE IMPORTANCE OF CHANNELS 263FIGURE 17.9
A ghostly
armada over
the Greenland
landscape.
Alpha Channels: Where Masks
Are Stored
Masks are stored in the Channels palette and are
called alpha channels. Photoshop and other
advanced image software (Freehand or Corel
Photopaint) enable you to work with alpha
channels. Because color channels are also found
in the Channels palette, it is important to know
that the two have little in common.
Color channels contain the color information
about an image. The information in color chan-
nels is part of the image. Color channels are visible in the image. However, masks
stored in alpha channels are not part of the image; they are never seen in the
image. Alpha channels are merely storage areas for masks—nothing more—and
masks are just editing tools that help create selections (see Figure 17.10). You never
see the mask itself in the completed image.
Here are the different types of channels:
■ Color channels. The Red, Green, and Blue channels and the RGB (compos-
ite) channel are part of every RGB image. CMYK images have five channels,
and LAB images have four channels. These types of channels are all related
to color information.
■ Adjustment layer masks. The channels appear when corresponding
adjustment layers are selected in the Layers palette. Only one adjustment
layer mask is displayed at any time, no matter how many adjustment layers
the image contains.tip
When you create an effect,
make sure you move the
adjustment layers slightly
away from each other so
their effects are not exactly
superimposed.