The origins of the alpha channel

In this exercise I'm going to introduce you to the Alpha Channel.…I'm looking at the final version of the toucan from the previous chapter, I've…gone ahead and called this file Last- seen toucan.psd and I'm going to switch…over to my Channels panel.…Notice that I'm seeing all of my channels in grayscale, that's very important,…by the way, if you're still seeing errors in color then press Ctrl+K or…Command+K on the Mac to bring up the Preferences dialog box.…Switch to Interface and turn off the Show Channels in Color check box.…Mine is already off so I'll go ahead and click the Cancel button.…

Now in addition to the color bearing channels red, green, and blue in this case,…the ones that actually contribute to the colors inside the image we have these…extra so-called Alpha channels.…Now an Alpha Channel can contain a mask which is typically a grayscale…representation of a selection outline.…It may contain a layer mask which conveys transparency to a layer, or it may…contain some other kind of mask.…