Chapter 3: Undo and History

Overview

Photoshop introduced the History palette in version 5, and in doing so redefined the entire concept of "Undo." The History palette goes far beyond simple undoing and redoing of steps in a linear fashion. With Photoshop you can instantaneously jump from one step to any other step in the sequence ” digital time travel, if you will.

The History palette's unique capabilities include:

• Undo-independent stepping: "Undo-independent," means independent of the Undo command. Every program with multiple undoes can step forward and backward, but Photoshop's two keyboard commands ” Ctrl+Alt+Z ( z -Option-Z on the Mac) to move backward, and Ctrl+Shift+Z ( z -Shift-Z) to step forward ” work independently of the Undo command. This means even back stepping is undoable.

• Before and after: Revert to a point in history to see a before view of your image and then fly forward to see the after view. From then on, Ctrl+Z ( z -Z on the Mac) becomes a super-undo, toggling between the before and after views. The opportunities for comparing statesand changing your mind are virtually unlimited.

• Dynamic time travel: Using the History palette's slider, you can dynamically move forward and backward through operations. It's as if you recorded the operations to videotape, and now you're rewinding and fast- forwarding through them.

• Sweeping away the mistakes: Select a point in the history of your image and paint back to it using the History brush. This capability takes Photoshop's filters to a whole new level. For example, you can apply a filter in one step, and then revert back to a point just before it and use the History brush to paint the filter effect back into your image selectively ” taking advantage of any and all brush options Photoshop offers.

• Take a picture, it'll last longer: You can save any point in the History palette as a snapshot. That way, even several hundred operations after that point in history is long gone, you can revisit the snapshot.

• This is your life, Image A: Histories are unique to each image you have open. So after performing a few hundred operations on Image A, you can still go back to Image B and back step through operations you performed hours ago. Be forewarned ” the history remains available only as long as an image is open . Close the image, and its history is lost.

• Undo the Revert command: The History palette tracks the Revert command. So if you don't like the image that was last saved to disk, you can undo the reversion and get back to where you were. Also notice that when you choose File Revert, Photoshop does not ask you to confirm the reversion. There's no reason for a warning because Revert is fully undoable.

Now, if only the History palette could travel forward into the future ” to, say, the point at which your latest project is finished and the check's cleared. On second thought, maybe not. The day Adobe can figure out how to do our work for us, clients will hire Photoshop and stop hiring us.