Photoshop® CS4 Bible

6.1. The Undo Command

Similarly to the way it functions in most software packages, in Photoshop the Undo command removes the very last action that was performed. To use the Undo command, choose EditUndo, or press Ctrl+Z (.cmd;+Z on a Mac) on your keyboard (those keyboard shortcuts should already be etched into your muscle memory).

The Undo command is a little bit confusing, because the command itself is undoable. That means if you undo an action, and then choose Undo again, you'll undo what you just undid, making that undo into a redo. Make sense? Thought so. This is one area where Photoshop differs from most other software packages. Usually, choosing Undo repeatedly steps backward through the last several actions that were performed; whereas in Photoshop choosing Undo multiple times goes back and forth between undoing and redoing the last action. It might be a little disconcerting to new users of Photoshop, but fear not — there is a way to have your multiple undos in Photoshop, and it's called the History panel.

Briefly, the History panel records each action performed in Photoshop since you opened your document — up to a limit (more on that later). You can click on any of these stored states to return the document to the way it appeared when that action was performed. You can step ...