Saving Selections in Adobe Photoshop CS5
The term alpha channel sounds complicated, but it’s simply a saved selection. Depending on the mode you’re in, you already have several channels to contend with. A selection is just an extra channel that you can call on at any time.
To create an alpha channel, follow these steps:
Create a selection that you want to save.
Choose Select→Save Selection.
Name the selection and click OK.
An additional named channel that contains your selection appears in the Channels panel.
To load a saved selection, follow these steps:
Choose Select→Load Selection.
The Load Selection dialog box appears.
Select a named channel from the Channel drop-down list.
If you have an active selection and then choose to load a selection, you have additional options. With an active selection, you can select one of the following options:
New Selection: Eliminate the existing selection and create a new selection based on the channel you select.
Add to Selection: Add the channel to the existing selection.
Subtract from Selection: Subtract the channel from the existing selection.
Intersect with Selection: Intersect the channel with the existing selection.
Other Adobe applications, such as InDesign, Illustrator, Premiere, and After Effects, also recognize alpha channels.