How to View an Image’s Various States in Photoshop CS6
In Adobe Photoshop Creative Suite 6, you can move back to any state listed in the History panel, remove a state to cancel a step, or perform other time-travel stunts by using the History panel. Here are some basic time-shifting techniques that you can use.
How to go back to a particular state
To go back in time and resume editing at a particular point, just click the state to which you want to return. All subsequent states appear gray, or undone. Then, begin editing your image. As soon as you perform a new step, all the states that follow your reentry point vanish. It’s like applying the Undo command (Ctrl+Z on a PC, Command+Z on the Mac) to a group of steps.
If you intentionally (or accidentally) begin editing while a previous state is highlighted, and then you change your mind, immediately undo your action — press Ctrl+Z (Command+Z on the Mac). The subsequent steps that were removed reappear.
How to review your image at different states
To review your image at previous states, just click the state you want to see. (You can also drag the active state marker up and down the list.) The document image immediately changes to reflect that earlier state. You can move back and forth between any two points in the history list. As long as you don’t make any editing changes during this jaunt, your current history list is preserved.
How to purge and clear all states
To remove a state and all the steps that follow it, select the state and then press the Delete key or click the trash can icon.
You can clear all the states except the most recent one from the panel by selecting Clear History from the panel pop-up menu. (Click the down arrow in the upper-right corner of the panel to make this menu appear.) All your snapshots will be preserved. You can undo your clearing only if you choose Edit→Undo immediately after you execute the command.
You can also delete all the states except the last one in the history list and keep the snapshots you’ve saved by choosing Edit→Purge→Histories. You can clear or purge your history list when you no longer need the states it includes — if you either want to save memory or return to the original state of your document.
When purging, just be sure that you really, seriously are not interested in going back later to make changes because you can’t undo this command.
How to navigate the history list
You can move up and down the history list, even if the list isn’t visible on your screen. Choose Edit→Step Forward to move forward in the history list and Edit→Step Backward to move back. The best way to access these commands is to use the keyboard shortcuts:
Press Alt+Ctrl+Z (Option+Command+Z on the Mac) to move backward (up the history list).
Press Shift+Ctrl+Z (Shift+Command+Z on the Mac) to move forward (down the history list).