The history palette is an extremely useful and valuable palette in Photoshop. As you work with an image, changes made to the image (states of the image) will be recorded in the history palette. You can use the history palette at any time to delete history items, essentially undoing the changes that correspond to the history items being deleted.

In Photoshop CS, the default number of image states is 20. This means that you can undo up to 20 changes you have made (states) to an image.

If you want to remove an image state, (undo a change), simply right click on the item in the history list and select delete from the menu that appears. You can do the same thing by dragging and dropping a history item into the trash can at the lower right of the palette.

If you want to create a new document from a history state, just drag the history item to the new document icon (the leftmost icon in the bottom bar in the history palette). A new image canvas containing the chosen history state will appear on the Photoshop screen in addition to the original.

If you make more changes to an image than there is room for in history, you may lose some of your history states. The earliest changes to the image will be removed to make room for more recent changes. You can, however, ensure that a given state lasts the duration of your time working with an image, by making a snapshot of that particular state. To make a snapshot, drag and drop the state of your choice to the camera icon in the bar at the bottom of the palette. Remember that when you close an image, you lose all history items, including snapshots.

If you click the menu arrow at the upper right of the history palette, you will display a number of options for working with your history items. The clear history option in this menu will clear all history items (remove all changes) except for the most recent.

When you perform actions in Photoshop, like making selections, cropping regions of an image, or working with effects, you can record them. If there is a sequence of actions that you repeatedly use, you can play back the recorded sequence, and have the actions performed automatically.

The Actions palette provides access to stored actions and to options for recording and playing back actions. There are also actions that come preset with Photoshop CS that are accessible from the actions palette.

To see these preset actions, click the small blue triangle by the folder icon named Default Actions.atn. This will reveal the folder’s contents as a list of action sets.

If you continue to click the small triangles, you can reveal the steps in an individual set of actions. To remove a step from a set of actions, clear the checkbox next to the step you want to avoid. When you play the set of actions, the step with the checkmark removed will not be implemented. If you see an icon next to the checkmark in front of an action step, it means that this particular step involves a dialog box that will need a user response to continue.

To apply a set of actions to an image, open the image, click on set name in the actions list, and then click the play button (the right pointing arrow head in the bottom bar of the palette).

If you click the menu triangle in the upper right of the palette, you will see options for configuring, recording, or playing actions.

Creating and using actions is an advanced Photoshop topic, which will be dealt with in detail in the advanced manual.