Using the Undo Command in Photoshop

Your first stop in your journey through time is the Undo/Redo command. This command simply reverses the last action you took or reapplies it if you just undid something. For example, if you apply a brush stroke you don’t like, use Undo to remove that stroke. Then if you immediately change your mind, you can redo it.

To undo your last action, choose Edit➪Undo or simply press Ctrl+Z (Ô+Z on the Mac). Use Undo/Redo to toggle an effect on and off to compare the before and after effects quickly. For example, you can apply a filter, examine the results, and then flip back and forth between the filtered and unfiltered version by pressing the Undo/Redo shortcut keys rapidly. When you decide which way to go, stop. This procedure works best if you’ve chosen to press Ctrl+Z (Ô+Z on the Mac) to apply both Undo and Redo.

Remember that Undo/Redo works only for a single command. If you do anything else after applying a command and then change your mind, you have to resort to one of the other timetravel techniques described later.

If an action can’t be undone or redone, Undo/Redo is grayed out and unavailable. For example, if you apply a brush stroke and then save the file to your hard drive, you can no longer undo the brush stroke. (However, you can use the History palette to remove the brush stroke.

If you want to free the memory used by the Undo command, choose Edit➪Purge➪Undo. If the item is grayed out, the buffer is already empty. Note that this action cannot be undone, so only do it if you notice Photoshop acting sluggish.