Chapter 3. Layers: The Key to Nondestructive Editing
Photoshop gives you two ways to edit files: destructively and nondestructively. Destructive editing means you’re changing the original image—once you exceed the History panel’s limit (The Power of Undo), those changes are (gulp) permanent. Nondestructive editing means you’re not changing the original file and you can go back to it at any time. Folks new to image editing tend to use the first method and experienced pixel-jockeys the second—and you’ll likely see a tiny cloud of smugness floating above the latter.
When you’re working in Photoshop, you need to keep your documents as flexible as possible. People (even you!) change their minds hourly about what looks good, what they want, and where they want it—all of which is no big deal if you’re prepared for that. If not, you’ll spend a ton of time redoing what you’ve already done from scratch. To avoid that kind of suffering, you can use layers, a set of stackable transparencies that together form a whole image (see Figure 3-1). Layers are your ticket to nondestructive editing.
With layers, you can make all kinds of changes to an image without altering the original. For example, you can use one layer to color-correct your family reunion photo (Chapter 9), another to whiten Aunt Bessie’s teeth (Whitening Teeth), and yet another to add a photo of the Great Pyramid to make the reunion look like it was held in Egypt instead of at the local park (Sky Swapping). Using layers also lets you ...