Photoshop Top 40, Feature #15: Alpha Channels

UPDATE: The good folks at have replaced the bad old corrupted version of this video with a new one that plays properly. Thanks to everyone who let me know that the old one was messed up!

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) 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 this week’s feature, 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. To learn more, check out my Photoshop CS4 Channels & Masks book published by Deke Press in association with O’Reilly Media. Or play the video at the top of the page.

All photographs used in this video come to us from image vendor Fotolia. The clouds photo is image #14267355 from ManInBlack. The curly-haired model (which some of you may remember from Feature #18: Smart Objects) is image #12363549 from Valua Vitaly. For an exclusive dekeOnline deal, click this link.

(For a list of all Photoshop Top 4 videos thus far, click here.)

Photoshop Top 4 is available as a downloadable podcast from iTunes. Click here to subscribe. dekePod subscribers will get the videos automatically.

Next entry:Martini Hour 047, In Which Deke Displays His International Interviewing Skills

Previous entry:Martini Hour 046, In Which Colleen Discovers Her Dutch Counterpart


  • excellent

    Nice one again Dekeapotamus. I have watched your other masking videos and somehow completely forgot about the opacity brush step. Thank you for all of your time and effort! Here’s to looking forward to next Tuesday.

  • Heal fast

    That’s not a great way to start the year Deke… I hope you took the time to enjoy the view!

    BTB; that was a witty comment.

  • Great Design

    It’s really a great design. Thank you for your information for me.

  • Top Tip #41

    Deke… Next time use paths and refine the edges, ‘before’ falling off!

  • Date misdated

    I just downloaded the podcast and somehow it is dated 05/01/09, so now it is lost at the bottom of the list, between episodes 11 and 12.
    Is this the last one?. Is this one of the ‘Top 40’s’ list for CS3? Or CS2?

    Is it my machine?

    BTW, excellent podcast, as usual.


    Friends are the family we choose

  • Flash audio/video out of sync

    Please help. I am having difficulties playing some of your videos, and in particular Feature #15: Alpha Channels. The video is out of sync with the audio when I play it (slow video playback).

  • I’m seeing the same thing.

    I’m seeing the same thing.  Video is super-slow.  I even went to the ‘base’ Youtube webpage with the same results.  Other deke videos worked fine for me, though.


  • Me too

    video is slow motion vs. audio.

  • I’m seeing it too

    Which is curious, given that it played just fine a few days ago.

    Possibly some YouTube weirdness. I’ll look into it.

    (By which I mean, stop being so old school. Out-of-sync audio with ponderously slow video is the latest rage. All the kids are doing it.)

  • This movie is toast

    Near as we can tell, something got corrupted on the YouTube end. Probably the appearance of my face busted things.

    My producer is in the midst of uploading a new version of the video. Once that’s complete, I’ll update the links and we’ll hopefully have things all straightened out.

    Check back here midday tomorrow!

  • Unwatchably corrupted.

    This looks like a good episode, as they all are, but the dog ate the video.  The voice comes in first, then later the slowwwed down video.  I struggled through about a third of it and gave up. 

    One favor:  If you post a fixed version, please note that it’s been fixed, so we know.

    Love the series.  This is a king hell bunch of tutorials.  Many thanks for them.

    Tom B

  • Still waiting for a fix

    Had an unexpected delay. Will let everyone know when it’s better.

    Dang, ti’s a good video, too! Very frustrating . . .

  • Feature #15: Alpha Channels is fixed!

    We finally managed to resolve the problems with this video! Now the audio and video actually play in sync with each other—what a country!

    Apparently, the YouTube gods were waiting until my knee fully healed.

  • It’s really a great design.

    It’s really a great design. Thank you for your information.

  • Nice Video.

    Btw, nice video u have

    Karen W Anderson

  • New Video

    Hi.  I am completely impressed with the video.. any new ones especially about Photoshop CS5 editions?

  • Very good article. I enjoyed your post very much. Thanks for sharing so much useful information.