June 12, 2011, 4:03 a.m.
posted by lordnikon
The History palette records every command and operation that you use in Photoshop. This includes brush strokes, Foreground and Background color changes, blending mode changes, and anything that you do that affects the image window. Figure shows the History palette with a selected history state. By default, the History palette is grouped with the Actions palette at the right side of the program window. If you don’t see the History palette, choose Window>History.
You can do many things with the History palette. I don’t list all of them here, but the following list gives you an idea of the power and scope of this great palette:
Move back to a previous history state by selecting it in the History palette. When you click the previous history state, the image in the image window reverts to that previous state. You can set how many history states the History palette records by choosing Edit>Preferences>General (Windows) or Photoshop>Preferences>General (Mac), and then entering a number from 1–100 in the History States text box.
Create a snapshot of an image before performing a complicated editing procedure by clicking the Create New Snapshot button at the bottom of the History palette. This snapshot saves the entire state of the image, including layers, blending modes, active selections — you name it. If you make a mistake or want to revert to the state saved by the snapshot for any reason, simply click the snapshot at the top of the History palette. Turn to Technique 7 to find out more about creating and using snapshots.
Select a previous history state as the source for the History Brush and Art History Brush by clicking in the left column next to the desired history state. When a history state is set as the source, any painting that you do with the History Brush or Art History Brush restores those areas to the selected history state.
The fourth bullet point is the focus of this technique.