A fairly concise definition of nondestructive editing, from “Real World Adobe Photoshop CS3,” Blatner, Chavez, and Fraser, 2008, p. 652. “The Nondestructive Workflow…work nondestructively whenever possible, using tools like adjustment layers and masks to keep our options open as long as possible. With Smart Filters and the enhancements to Smart Objects, particularly when it comes to raw camera images, Photoshop CS3 makes it possible to keep a wide range of edits in a reversible state, so that you can back out of them at any time. Here are all of the typical image-editing steps using the nondestructive editing features in Photoshop CS3 [accompanying figure is titled “A Photoshop document built nondestructively” and shows Photoshop layers: base image raw file Smart Object modified by Smart Filters, such as Shadow/Highlight, with patching and other layers, such as curves, above the base]
“Using these techniques, you can, at any time, strip away every last edit and return to the original base image, or adjust the intensity of any edit whenever you like. It’s an astounding degree of flexibility, but again, pushing nondestructive editing this far can eat up your hard drive space and RAM in a hurry. To mitigate this, you can head for a middle ground where you rasterize some layers into pixels when you’re happy with them.” (emphasis added) (edited to correct copyright date)