From the course: Photoshop: Channels and Masks

Mastering channel operations - Photoshop Tutorial

From the course: Photoshop: Channels and Masks

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Mastering channel operations

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- For the last several movies, we've relied on Photoshop to see the image for us. We've asked its various automated commands to evaluate image data, luminance transitions, and edge details, and come up with a selection outline or layer mask, which is great. And I gotta say kudos to Photoshop for providing us with these cutting edge commands, but it's not the only way to work. Inside any given RGB file, you have three unique grayscale images, and more often than not, they see the image from perfectly reasonable, albeit very different perspectives. That reasonable difference goes to the heart of this chapter. If at least two channels are of sound quality, provide good contrast between foreground and background, and reveal the photograph in different ways, might we not get a better view of the image by combining them? If two heads are better than one, surely the same can be said of two channels. Enter the Calculations command, which permits you to blend one channel with another according to any of 22 blend modes. This count does not include normal, by the way, which is the equivalent of turning the blend mode off. While more conceptually challenging than anything we've seen so far, the Calculations command expands your range of creative options by an order of magnitude. With some experience, you can build a better base alpha channel, complete a given mask in a shorter period of time, and approach each and every masking job with a higher degree of confidence that you will ultimately achieve success. Unlike the other commands we've seen, the Calculations command resides in the Image menu. This is in part a function of its age. Calculations is very old, from the ancient days before layers, and an acknowledgment that like the other commands in the Image menu, Calculations looks at the entire image at a time. It sees every layer, it sees every color channel, it sees every alpha channel, it sees layer masks, it sees transparency masks. Simply put, it sees everything. It really is Photoshop's version of the Wisdom of the Ages. The Calculations command is uncommonly powerful, but it is not what you might call friendly. It will seem daunting at first, but trust me, I will make it make sense. In the very next movie, I diagram the command on an option by option basis. After that, we will visit the command multiple times for multiple purposes. Now, the Calculations command is not for the faint of heart. I won't judge you if you don't last beyond this movie. And based on our internal data, I'm guessing many of you won't. But for the those of you who do, now is when things get really super interesting. Now is when those of you who stick with me race forward and rise up to the front of the pack.

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