As you may be guessing by now, masks, selections, and channels are all related in a sense. You can convert a mask to a selection; you can convert a selection to a mask, and you can save a selection to a channel. What you may not have guessed is that you can also save a mask as a channel. As a matter of fact, any time you create a quick mask, it is stored on a special new channel in the channels palette.

The channels that are used to carry selection or mask information are called alpha channels. When you save a selection you are actually saving it on an alpha channel. When you create a quick mask in Photoshop CS, you are automatically storing it on an alpha channel as well.

Take the following image as an example.

Here you can see a rectangular selection around the palm leaves. If you click the Quick Mask button in the toolbox, a mask will appear around the selection.

If you look at the channels palette, you will see a new channel has automatically been created for the quick mask.

If you were to now save this image under a TIFF or PSD format, the quick mask (alpha) channel will be saved with it. When you open the image at a later date, you can pick up editing the mask where you left off.

To rename an alpha channel, whether it carries a mask or a selection, just double click on its name in the channels palette. The name will then be highlighted in blue and editable.