Black pixels in an alpha channel correspond to masked, or non-
selected, pixels in an image. White pixels correspond to selected pix-
els. Gray pixels correspond to various levels of selection, with lighter
grays corresponding to greater selection than darker grays.
Note: If you want black pixels to correspond to selected, rather than
masked pixels, click Selected Area in the New Channel or Channel
Options dialog box.
Using the Channels palette
The Channels palette displays the channels contained in a paint
object when the paint object is in edit mode. The palette also displays
the channels contained in any object that has a channel mask when
you edit the mask.
You can use the palette to create, duplicate, and delete channels; to
change channel options; and to make selections by loading channels.
To open the Channels palette: Choose Image > Show Chan-
nels.
Composite channel
Select the first channel in the palette to make
all color channels visible and active. Paint objects in CMYK Color,
RGB Color, and LAB Color modes have composite channels. The
channel is labeled CMYK for a CMYK Color image, RGB for
an RGB Color image, and LAB for a LAB Color image.
Paint objects in Indexed, Grayscale, Black & White, and Duotone
modes have single channels. A vector object that has a channel mask
has an object channel.
Color channels
Color channels appear below the composite chan-
nel in the Channels palette. Color channels store the color data in an
image. The image mode determines the number of color channels.
CMYK Color images have Cyan, Magenta, Yellow, and Black color
channels. RGB Color images have Red, Green, and Blue color chan-
nels. LAB Color images have A and B color channels and a
Lightness channel. Multichannel images have numbered channels
that contain grayscale pixels only.
Alpha channels
Alpha channels contain grayscale pixels which
can represent a selection. You can use alpha channels to create chan-
nel masks. Any paint object can have alpha channels. However, paint
objects in Black & White mode must have a channel mask before
they can contain alpha channels.