Master Masking with Photoshop's Alpha Channels


Masking an image is like poking a hole in the background to reveal the foreground. I use this analogy because A) I’m growing a bit weary of the “white reveals, black conceals” line; B) I’m just coming off a ski vacation in Big Sky, Montana, at the end of which I wiped out on a bunch of rocks at the top of the 11,166-foot Lone Peak (see diagram below) and poked a purple-looking hole in my knee; and C) masking is exactly like that, except not so purple.

What does that have to do with alpha channels? The modest but powerful alpha channel serves as a sort of cozy base camp for the hole-poking mask. That is to say, a single alpha channel lets you create a mask, refine that mask, perfect it, and save it for later use. Watch the video below to see what I mean.

If the above video doesn’t play for you, you can watch it on YouTube.
To learn more, check out my Photoshop CS4 Channels & Masks book published by Deke Press in association with O’Reilly Media.

  • crusnak says:

    I’d love to see this technique accomplished with a much more complicated subject to mask.

  • Anonymous says:

    Is there a way to post this video anywhere else but on YouTube? I work in a corporation where that site is blocked from employee access.

  • Terri Stone says:

    No, I’m afraid that YouTube is where this video lives.

    Terri Stone
    Editor in Chief,

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