Photoshop CS4: The Missing Manual

Chapter 5. Controlling Color with Channels

At the heart of any Photoshop file lie channels—storage containers for all your image’s color information, saved selections (Saving a Selection), and instructions regarding special printing inks. Channels sound intimidating at first, and folks have been known to shudder at their mention and avoid them completely. But to really understand Photoshop, you need to understand channels. Luckily, you don’t need a PhD—just a little patience.

This chapter gets a little technical at times, but if you soldier through, you’ll be rewarded with wisdom that’ll help you perform some amazing pixel wizardry. You’ll get that warm, fuzzy enlightened feeling as you learn to:

• Use channels to make complex selections (Basic Channel Stunts).

• Perform highly targeted color adjustments (see the figure on Making Colors Pop).

• Create stunning grayscale conversions (The Lightness Channel).

• Map one image to the contours of another (Mapping One Image onto Another).

• Sharpen your images without introducing noise (Sharpening Individual Channels).

• Save a selection so you can use it later (Single-Channel Modes).

And that’s just the tip of the iceberg. Everything you do in Photoshop involves channels, so it’s important to get to know them. If you understand how Photoshop does what it does, you can make it do even more in less time and with less effort. That’s called working smarter, not harder—which is why, dear grasshopper, you’re reading this book.

To understand how channels work, you ...