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 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.

. Tagged with:


Found the video.

Andre Noun
I found the video that I wanted. Thank you again.

Visual Calculations

Hi, Deke. Glad you liked the mock-up dialog box. As you mentioned in this movie, Calculations are "daunting and powerful." To make it less daunting, and thus more accessible to new users, I've recommended an interface enhancement to Adobe: Visual Calculations (to see the mock-up, click here). When I use Calculations for masking, most of my time is spent clicking through the drop-down menu of blend modes to see the outcome in the image window. If I could see all the results at one time, in one dialog, that would speed up my work flow. A more visual interface would also be more intuitive for users unfamiliar with Calculations, and may thus spur broader use of this valuable tool. You have the ear of Adobe, so feel free to improve upon and share this idea with the appropriate people. If other Deke fans feel this idea has merit, please let Adobe know of your interest by visiting Adobe's Feature Request page.

I think you're really onto something

It's big, and it would rather consume a typical monitor. But where masking in particular is concerned, it could really take the guesswork out of things.

voting for HD

Voting for HD, of course!!!

Ditto for Top 40 in HD

Many of the tutorials you provide require HD to see clearly what you are doing.

this is a useful feature -

this is a useful feature - but hard to understand.

I love what you can do with

I love what you can do with this!!

Blog it, Twit it, Facebook it

Photoshop top 40 is officially on itunes. Great!!!!!!!


hi everybody, sorry for going a little bit off topic but i want to say something that i hope will reach deke's ears :D well i am not a veteran when it comes to working with photoshop right now there are a lot of video tutorials on the internet about photoshop (the software) most of them (if not all) discussing how to manipulate one or more pictures into something "cool' well - here is the suggestion - i wanted to draw something from scratch. i know it is exponentially harder but there are times when you need to do that. so i searched and searched and all i found was how to draw a smiley face and other things like that (obviously articles or very poor videos) so deke or whoever reads this message, i think that this is a field that is not so well "exploited". maybe you can give this a thought and ... who knows ... maybe a new tutorial will appear on :) thanks, rares

Nice tutorials

Happy to find such a tutorial!

Very good tut...wish you

Very good tut...wish you could do after effects your style.

After Effects

Gotta check out Eran Stern, he's kinda silly and his brother is just down right goofy-love it.

I vote for full HD

It would be best if we can see you in full HD.

... i just accidentally found myself here... am i in heaven...?

golly - i ran upon a link to this site by accident...been here 5 minutes and it's like i'm back watching Deke teach me CS2... but 2 generations later. yay... just yay...

HD for sure

There's no way you can go back to lower resolution Deke. HD all the way. Same thing for the upcoming itunes podcasts. You forgot to tell people that you were still on Pixel Perfect with Bert this week. Love your work man.


If the HD button doesn't appear in the embed, visit the video's original youtube site by clicking the youtube logo watermark in the bottom right corner of the vid. That's how I watched it in HD mode, and it loaded unusually fast this time.

Looks like we've got a winner!

Smart Objects is so far in the lead Deke, I hope you're already gearing up to flood us with something new to Master (not that I don't have a lot of work left on some of the other things) that's part of the Photoshop puzzle. Thanks for doing such a great job with all the other installments to our knowledge bin! Mike Ducey


Want to see the rest right now! Quit holdin out on us, Deke!! Very cool, and, as always, very informative.


OK - so I did the first lesson and got it to work on one of my pictures, but now what??!! I'm dying out here waiting for the second step.

Deke: ACE Exam, 1-on-1?

Deke, you mentioned something about Q&A Free 4 All awhile back. I can't find where to contact you, but you seem to read these comments. I want to become an Adobe Certified Expert in PSCS4. Is your Photoshop CS4 One-on-One course (all 3 parts) appropriate training material for that purpose?

Hi hash3m :-)

I'm not Deke (as you can see by my girly hirsutelessness), but I'd say that Deke's training would be an integral part of your studies for ACE. Here's Adobe's study bulletin to help you identify what you need to learn: Good luck! :-D

Thank you!

It looks like I better run through 1-on-1 a second time to solidify it all, and grab a more topic-specific resource or two just in case...for the specialized aspects. Homeschooling ftw! Thanks again :) (In case anyone is wondering, the 3 part CS4 1-on-1 video course was incredibly more comprehensive than the resources Adobe suggests. It's 48 hours! I will continue to use courses for my prep. The CS4 Cs&Ms book is proving to be awesome as well.)

High Definition

The choice of people who prefer things in high definition.

of course HD

we want to see you in full HD :)


Even I've Watched the complete series of"Channels and masks" on Lynda ... I'm Still interested in further masking techniques Black Seals ... White Reveals...!