Editing History States | Photoshop CS Savvy

The primary purpose of Photoshop s history is to keep the editing process dynamic. There are several ways to use the History palette to keep the workflow flexible so that you can experiment freely and confidently.

For all history operations, to target a state, click it in the History palette.

Deleting History States

Sometimes you ll want to delete a state. Try any of these methods :

Drag the state to the trash icon at the bottom of the History palette.
Target the state, and then choose Delete from the palette s pull-down menu or click the trash icon.
Target a state. All states beneath it will be grayed out. Perform an edit to the state, and the grayed-out states will be purged.
Choose Clear History from the palette s menu to clear all the states except the last state. Clearing the history retains the snapshots.
Choose Edit ’ Purge ’ Histories. All the states but the one at the bottom of the list will be deleted. This option cannot be undone. The snapshots are retained.

Working with a Nonlinear History

If you delete a state, then by default, you ll also eliminate all of the more recent states (those underneath it in the palette). You can, however, change this default. From the History Palette pull-down menu, choose History Options and check Allow Non-Linear History box.

The Allow Non-Linear History option gives you the ability to eliminate or edit a state in the History palette and still preserve all the states below it in the stack. For example, you can target a state, make changes to it, save the altered state as a snapshot, target the most recent state, and continue working on the image. Experiment carefully with this option, because you can produce strange and unexpected results.

Using the History Brush

The History Brush tool enables you to paint with a chosen state. You can use the History Brush to reestablish portions of a state even if you ve edited them later. The Source column at the far left of the History palette tells Photoshop which state you want to paint with.

For example, suppose you paint a brush stroke on an image. As you continue to work, each time you perform an operation, a new state is added. If you later decide that you want to retain only half of that original brush stroke, here s how to do it:

Open the History palette.
Look through the states from bottom to top in sequence, until you find the state where you made the brush stroke.
Click the Source column to the left of the previous state, just above the state with the brush stroke. A History Brush icon appears in that column.

By choosing the state previous to the brush stroke as the Source, you are telling the History palette that this is what you want the corrected portions of the image to look like. You are actually painting with the previous state in order to eliminate a portion of the brush stroke.
Choose the History Brush from the Tool palette and retarget the most recent state.

If the Allow Non-Linear History option is not selected, you must target the last state in the history if you want to avoid losing the intervening states.
Paint over the portion of the brush stroke you want to cover up with the chosen previous state.

Painting with a Snapshot

You can use a snapshot in a similar manner when using the History Brush. Suppose you take a snapshot of an edit you made with a filter. After undoing the filter or eliminating its state, you can selectively apply the snapshot to specific portions of the image. If you save the snapshot as the full document or a single layer, the History Brush will paint from one layer to the corresponding layer on the targeted state. (The color section of this book includes a demonstration of painting with the History Brush. See Figures C11a “c.)

To paint with a snapshot:

Apply a filter, brush stroke, color adjustment, or any other effect to an image.
Choose Make Snapshot from the History Palette pull-down menu.
Choose Edit ’ Undo to undo the effect.
Click the Source column next to the new snapshot.
Choose the History Brush from the Tool palette. Choose a brush size and specify opacity and other brush characteristics in the Options bar.
Paint on the areas of the image that you want to affect.

Working with Other History-Editing Features

There are a couple of history-editing features scattered throughout the program that you should be aware of:

The Eraser Tool With the Erase To History option selected, the Eraser tool erases to a designated History state. You must designate the History state by clicking the Source column in the History palette next to the state you wish to erase to.

Fill from History Choose Edit ’ Fill ’ Use History to fill a selected area with a designated state. You must designate the History state by clicking the Source column in the History palette next to the state you wish to fill with.

Using the Art History Brush

This tool is called the Art History Brush because it s quite handy for creating instant Impressionist effects (Impressionism being an important movement in the history of art). And I mention it here only because it is in the History Brush fly-out on the Tool palette. But it does not use the history to alter the image as the History Brush does, except, like any other tool or operation, its effects are recorded as a state each time you apply it. (See Chapter 10 for a complete description of the Art History Brush tool and a demonstration of what it can do.)