The Snapshot command lets you make a temporary copy (or snapshot) of any state of the image. The new snapshot is added to the list of snapshots at the top of the History palette. Selecting a snapshot lets you work from that version of the image.
Snapshots are similar to the states listed in the History palette, but they offer additional advantages:
You can name a snapshot to make it easy to identify.
Snapshots can be stored for an entire work session.
You can compare effects easily. For example, you can take a snapshot before and after applying a filter. Then select the first snapshot, and try the same filter with different settings. Switch between the snapshots to find the settings you like best.
With snapshots, you can recover your work easily. When you experiment with a complex technique or apply an action, take a snapshot first. If you’re not satisfied with the results, you can select the snapshot to undo all the steps.
To select a snapshot, click the name of the snapshot or drag the slider at the left of the snapshot up or down to a different snapshot.
To rename a snapshot, double-click the snapshot and enter a name.
To delete a snapshot, select the snapshot and either
choose Delete from the palette menu, click the Delete icon , or
drag the snapshot to the Delete icon.
The
History Brush tool lets
you paint a copy of one image state or snapshot into the current
image window. This tool makes a copy, or sample, of the image and
then paints with it.
For example, you might make a snapshot of a change you made with a painting tool or filter (with the Full Document option selected when you create the snapshot). After undoing the change to the image, you could use the History Brush tool to apply the change selectively to areas of the image. Unless you select a merged snapshot, the History Brush tool paints from a layer in the selected state to the same layer in another state.
The History Brush tool copies from one state or snapshot to another, but only at the same location. In Photoshop, you can also paint with the Art History Brush tool to create special effects.
Specify the opacity and blending mode.
Choose a brush and set brush options.