Photoshop Top 40, Feature #33: Calculations

As friends of this site know, Tuesday is Photoshop Top 40 day. And this Tuesday is no exception. Today's video covers one of the oldest, most abstruse, downright incomprehensible commands in all of Photoshop: Calculations. Found under the Image menu, the Calculations command lets you mix two existing channels in an image--say, Red and Blue--to create a new alpha channel that will serve as the basis for a mask. And while it takes a fair amount of time and effort to come to terms with the feature, Calculations is one of the most powerful masking commands in all of Photoshop.

Besides the fact that it teaches you how to use Calculations, this video is remarkable for three reasons:

• This marks the first of three free Top 40 videos in which I'll build a full-blown mask from scratch. (What are the other two mask-savvy features? You'll just have to wait and find out in the upcoming weeks.)
• Unlike other masking videos posted to this site--in which I separate a foreground image from a white background or blue screen--this woman with all her hair appears against an unevenly lit backdrop. The result is a slightly more challenging project.
• I drew previous Top 40 videos from the low-resolution YouTube feed. This one is the product of the HD feed, which should hopefully result in a crisper picture. It does however require a speedier connection. Let me know which you'd prefer in the future. (I might even go back and relink the old posts.)

The base photograph comes to us from Stas Perov of image vendor Fotolia.com. Click this link for a special deal.

(For a list of all Photoshop Top 40 videos thus far, click this link.)

Oh, and we're just about ready to release Photoshop Top 40 as an iTunes podcast, starting all the way back with Feature #40: Reset and Purge. I'll keep you posted.