The Digital Zone System by Robert Fisher

The Digital Zone System by Robert Fisher

Author:Robert Fisher
Language: eng
Format: epub
Publisher: Rocky Nook, Inc.
Published: 2012-06-12T16:00:00+00:00


In essence, layer masks are a type of alpha channel, but applied to a layer rather than saved as a new channel. That brings us to the next tool in the DZS toolkit: alpha channels.

Alpha Channels

An alpha channel is really nothing more than a saved selection. Alpha channels, or saved selections, are used in cases when you’re likely to want to use a selection more than once and you don’t want to have to go back and recreate the selection.

Alpha channels show up in the Channels palette below the RGB composite and individual R, G, and B channels of an image. These channels work in the same way as any mask: Black hides, white reveals, and gray partially reveals, depending on how deep the gray is. Going back to our previous image, if we take a look at the channels palette, below the RGB composite and individual color channels is something called Hue/Saturation Mask 1 (figure 4.18). It contains the same black, gray, and white sections as the layer mask. This is an alpha channel.

In this case, the alpha channel was created by the Hue/Saturation adjustment layer but is only temporary. It’s visible only when the adjustment layer is active. When you click on the main base layer, the alpha channel goes away. Clicking on the Hue/Saturation adjustment layer again will bring the alpha channel back. We can make it permanent—or permanent until we delete it—by saving the selection. To do this, go to Select>Load Selection, then Select>Save Selection. You can make this process easier by clicking on the small dotted circle at the bottom of the Channels palette, which will load the selection, and then clicking on the icon directly to the right of the dotted circle, which will save the selection as a channel. The selection is now saved as a channel and appears as Alpha 1 in the Channels palette (figure 4.19).



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