Adobe PHOTOSHOP 5.0, User Manual, Page: 260 / 400

CHAPTER 10 252
Using Channels and Masks
4
To change the opacity, enter a value between 0%
and 100%.
Both the color and opacity settings affect only the
appearance of the mask and have no effect on how
underlying areas are protected. Changing these
settings may make the mask more easily visible
against the colors in the image.
5
Click OK.
Using alpha channels
In addition to the temporary masks of Quick Mask
mode, you can create more permanent masks by
storing and editing selections in alpha channels
(see “About masks” on page 249).
An alpha channel has these properties:
•
Each image can contain up to 24 channels,
including all color and alpha channels.
•
All channels are 8-bit grayscale images, capable
of displaying 256 levels of gray.
•
You can add and delete alpha channels.
•
You can specify a name, color, mask option, and
opacity for each channel. (The opacity affects the
preview of the channel, not the image.)
•
All new channels have the same dimensions and
number of pixels as the original image.
•
You can edit the mask in an alpha channel using
the painting and editing tools.
•
Storing selections in alpha channels makes the
selections permanent, so that they can be used
again in the same image or in a different image.
Creating and saving alpha channels
You create a new alpha channel as a mask. For
example, you can create a gradient fill in a blank
channel, and then use it as a mask. Or you can save
a selection to either a new or existing channel.
To create a new alpha channel using current options:
Click the New Channel button ( ) at the bottom
of the Channels palette. The new channel is named
according to the sequence in which it was created.
To create a new alpha channel and specify options:
1
Do one of the following:
•
Alt-click (Windows) or Option-click (Mac OS)
the New Channel button ( ) at the bottom of the
palette.
•
Choose New Channel from the Channels
palette menu.
2
Type a name for the channel.
3
Select display options for the channel, as
described in steps 2 through 4 of the procedure on
Quick Mask options in “Using Quick Mask mode”
on page 250. Alpha channel options are identical
to Quick Mask options.
4 Click OK.
A new channel appears at the bottom of the
Channels palette and is the only channel visible in
the image window.