6. Working with the History Palette
What You’ll Do
Work with Linear and Non-Linear History
Control the Creative Process with Snapshots
Duplicate a History State in Another Document
Save the History State of a Document
Review the History State Text File
Combine the History Brush with a History State
Change the Eraser Tool into the History Brush
Introduction
Adobe introduced the History palette in Photoshop 5, and the graphic design world hasn’t been the same since. On an elementary level, the History palette gives you the ability to perform multiple undos. Think of History as having a magical mistake correction tool, which never wears out. However, the History palette does much more than give you the ability to go back in time and correct your mistakes. The History palette is simply a tool, but when you combine the power of the History palette with the History brush, and Art History brush, you have a trio of tools that can take your creative designs to the next level and beyond.
Adobe Photoshop gives you two options for using the History palette—linear and non-linear. The linear state helps you keep track of your recent steps, and erases and steps that interfere with a linear flow to the palette. The non-linear state preserves all the steps (linear or non), and is useful when you need to think outside the linear box.
Photoshop raises the bar on the History palette by giving you the ability to record and save the commands performed to a document in a History text document. Now, you can finally know exactly what you did to an image. And since the document can be printed, you can create history text documents of your favorite restoration and manipulation techniques, and save them as customized help topics.
In addition, when you combine the History brush with the History palette you have an awesome creative tool that can’t be beat. In fact, it’s even possible to convert the Eraser tool into a History brush.
Setting History Palette Options
Working with the History palette requires a firm understanding of how the palette functions, and what you can and cannot do with History. The History palette records your steps as you work through a document. A step is defined as a specific action, such as creating a layer, or adding a brush stroke. Every time you perform an action, a step is recorded in the History palette. The History palette gives you the ability to go back to a previous history state, which is the same as performing an undo command. You can perform multiple undo commands up to the number set in Photoshop preferences for the History States. In addition, the History palette creates snapshots of the document. Snapshots are images of the current state of the document. Snapshots are used in conjunction with the History and Art History Brushes to create special effects.
Set Number of History States
Click the Edit (Win), or Photoshop (Mac) menu, point to Preferences, and then click Performance.
Enter a value from 0 to 1000 for the number of steps recorded in the History States box.
Click OK.
Did You Know?
You can duplicate a History State. Hold down the Alt (Win) or Option (Mac) key, and then click the History State you want to duplicate.
For Your Information: Performing Multiple Undos
The History palette represents the ability to perform multiple undo commands as many as you choose for your History States. However when you press Ctrl+Z (Win), or 
+Z (Mac) you only move back and forth between the last command, just like a normal undo. To perform multiple undo commands press Ctrl+Shift+Z (Win) or +Shift+Z (Mac) to move forward through all your History steps, or press Alt+Shift+Z (Win) or Option+Shift+Z (Mac) to move backwards through the available History steps.
Set History Options
Select the History palette.
Click the History Options button, and then click History Options.
Select the check boxes for the History Options you want to use:
- Automatically Create First Snapshot. Creates a snapshot (image) when the document first opens.
- Automatically Create New Snapshot When Saving. Creates a snapshot every time you save the document.
This is useful for keeping track of the changes made to a document.
- Allow Non-Linear History. Allows you to operate History in a non-linear state.
- Show New Snapshot Dialog By Default. Opens a dialog box with options each time you create a new snapshot.
- Make Layer Visibility Changes Undoable. Instructs Photoshop to make changes made to a layer’s visibility undoable (New!).
Click OK.
Working with Linear and Non-Linear History
The History palette records each step performed on a Photoshop document in a linear fashion from top to bottom. However, the purpose of the History palette is not to simply record your progress through a document, it’s there to help you make changes and go back in time to correct mistakes. Photoshop handles the History palette in two ways-linear and non-linear. When you work in a linear History palette, clicking on a previous step causes all steps underneath to gray out. If you then add a step, the grayed out steps are removed and the new step is added to the bottom of the list. A linear palette is organized and is very RAM efficient, however, once a History Step is removed, it cannot be retrieved. When you work in a non-linear History palette, clicking on a previous step does not cause the steps underneath to gray out. If you then add a step, the new step is added to the bottom of the History palette. The new step represents the characteristics of the step you selected, plus any added actions. A non-linear palette is not organized and consumes more RAM memory. It’s advantage lies in the fact that History steps are not deleted; they are simply reorganized.
Work with Linear History
Select the History palette.
Click the History Options button, and then click History Options.
Clear the Allow Non-Linear History check box, and then click OK.
Work in the document until you have generated ten or fifteen steps in the History palette.
Move halfway up the History palette, and then click on a step.
The steps below the selected step turn gray.
Perform another action to the image.
The grayed steps are removed, replaced by the latest action applied to the image.
Work with Non-Linear History
Select the History palette.
Click the History Options button, and then click History Options.
Select the Allow Non-Linear History check box, and then click OK.
Work in the document until you have generated ten or fifteen steps in the History palette.
Move halfway up the History palette, and then click on a step.
The steps below the selected step do not change.
Perform another action to the image.
The new step is added to the bottom of the History steps.
Did You Know?
You can quickly purge the History States, and therefore recoup RAM memory. Hold down the Alt (Win) or Option (Mac) key, click the History Options button, and then click Clear History. But be warned, if you change your mind there is no undo available, you are stuck.
Controlling the Creative Process with Snapshots
The History palette contains more than just steps, it also holds snapshots. A History snapshot is an image of the document, as it exists at the time the snapshot was taken. The History palette can hold as many snapshots as needed, and they are not subject to the number of History States. That means they stay with the document throughout the creative process. By default, Photoshop takes a snapshot of the image when it first opens. This snapshot represents the original state of the image, before any adjustments or modifications are applied, and is identified with the file name of the image. It’s a good idea to create a Snapshot every time you make a major change to the image. That way if you want to start all over, all you have to do is click on the snapshot, and Photoshop returns you to the moment in time the snapshot was created. It’s like having your own personal time machine.
Create Snapshots
Select the History palette.
Click the History Options button, and then click History Options.
Select the Show New Snapshot Dialog By Default check box, and then click OK.
Perform several actions to the image.
Click the Create New Snapshot button.
Type a name for the new snapshot.
Click the From list arrow, and then click a save image information option:
- Full Document. Saves the entire visible image and all layers.
- Merged Layers. Saves only the merged layers.
- Current Layer. Saves only the active layer.
Click OK.
Duplicating a History State in Another Document
Here’s a tool to help you gain control over the creative process, and save you a lot of time and effort as well. The History palette lets you create new documents, based on a specific History step or snapshot. For example, you’re working on a complicated image, and you want to isolate a portion of the image in another document. This will not only help you reduce the clutter, but working on a portion of the image in a separate document creates a document with a much smaller file size, and that will help Photoshop work faster.
Create Another Document
Select the History palette.
Click on the snapshot or History State you want to use for the new document.
Click the Create New Document From Current State button.
Photoshop creates a new document based on the selected snapshot or state. The new document’s History palette contains one snapshot, and one state.
Important
Snapshots are not saved with the Photoshop document. When you reopen a document the History palette will display one snapshot of the current state of the image, and one History step.
Did You Know?
You can save RAM by using the History palette. When you create a new document using the History palette, it’s very RAM efficient, as opposed to the traditional copy and paste method.
Saving the History State of a Document
Photoshop gives you the ability to save the History states of a document as a separate text document, or as embedded metadata. Saving History is an excellent way to revive the steps you took to produce a particular design. Not only does the saved data record the steps you took; it also records the date and time each step was performed. This gives you a running record of the time spent on a document, which is useful for client billing purposes. Photoshop saves the history files as a standard text document, which can be opened in any text-editing program you choose.
Set Up to Save History
Click the Edit (Win) or Photoshop (Mac) menu, point to Preferences, and then click General.
Select the History Log check box.
Select the file type option you want to save log items:
- Metadata. Records the data as embedded metadata.
- Text File. Records the data to a text file.
- Both. Records the information as both metadata and text.
Click Choose, and then select location where you want to store the files.
Click the Edit Log Items list arrow, and then select the type of data you want to save:
- Sessions Only. Only records basic information, such as when the file was opened or closed.
- Concise. More information on actions taken.
- Detailed. The most data, including dates and times for actions, and each individual stet.
Click OK.
Reviewing the History State Text File
Photoshop creates the History State file on the fly, as you work each step precisely recorded. Photoshop does not create a separate data file for each working session, but a single file recording all work sessions. If you delete the original history data file, Photoshop will create a new file, and place it in the same location with the same name. Have you ever worked on a document, performing command after command and suddenly you step back, and really like the end result? Then you immediately grab a notepad and attempt to jot down all the steps—it’s always the most important step that you forget. Not with Photoshop and the History text file. The text document faithfully records each and every step. Later, after the project is finished, you can access the file and all your commands and steps will be listed.
Open the History State Text File
Close Photoshop.
Open the folder where the History text file is saved.
The default name is Photoshop Edit Log.txt, and the default location is the desktop.
Double-click to open the document with the default text editor.
NotePad (Win), TextEdit (Mac), or use a Word Processor, such as Microsoft Word.
- The date and time the file was opened is recorded at the top of the document.
- The steps performed are listed, one at a time.
- The date and time the file was closed is recorded at the bottom of the document.
Close your text editor program.
Controlling History States
The History palette is a fantastic tool! It can help you go back in time and correct errors, and even take snapshots of the image, which you can use to create new documents. But all great tools come with a price. The History palettes price is consumption of RAM memory. The more you use the History palette the more RAM memory it needs. If you find Photoshop slowing down on you, or if you get warning message stating that Photoshop is running low on RAM, you might want to try a few things to help gain back some of that lost efficiency. Photoshop lets you choose between 0 and 1,000 History states. That’s 1,000 undos, and while that might seem like a great thing to have, History states take up memory. You can also check on your settings. Non-Linear History requires more RAM memory to maintain. If you don’t require a non-linear history, then you can turn it off. Since Photoshop uses a lot of RAM memory (64MB just to open), it makes sense that Adobe would give you a way to manage the use of that memory.
Reset to Linear History
Select the History palette.
Click the History Options button, and then click History Options.
Clear the Allow Non-Linear History check box.
Click OK.
See Also
See “Setting History Palette Options” on page 120 for more information on setting the number of history states.
Purge RAM Memory
Click the Edit (Win) or Photoshop (Mac) menu, point to Purge, and then select from the following options:
- Undo. Removes the Undo states from History.
- Clipboard. If you have used the Edit menu, Copy and Paste commands, that information is still contained in RAM memory. Use this option to purge Clipboard memory.
- Histories. Select this option to purge all the states from the History palette.
- All. Wipe all RAM memory clean.
Important
The purge option has no undo. If you select any of the purge options, there is no going back, so make sure you want to purge memory.
Combining the History Brush with a History State
When Adobe created History, they advertised the fact that Photoshop now had more than one undo. Multiple undos are a great thing, however if all you use the History palette for is to correct your mistakes, you’re missing the whole idea of the History palette. The History palette does not stand by itself. It’s linked to the History brush. The History brush receives its information from a selected state or snapshot. For example, the History palette holds a snapshot of the way the image looked when first opened, and by default the History brush is linked to that snapshot. Think of the History brush as a photo restoration tool that always remembers the original state of the image. As you work on a document you will make changes. If during the current work session, you wish to restore the document back to its original (first opened) state, the History brush is your tool. The History brush is not just for correcting mistakes, but also for creating awesome special effects. All you need is a bit of imagination and a couple of additional snapshots.
Correct Mistakes with the History Brush
Select the History Brush tool on the toolbox.
Click the Brushes palette, and then click a size brush.
Drag the History brush across the image.
The places you drag are restored to their original (first opened) state.
Did You Know?
When you use the History brush on an image layer, you’re changing the information based on the chosen History state or snapshot. However, you will gain more control if you use the History brush in a separate layer. Just create and select a new layer, and when you use the History brush, paint in the layer. Not only does the separate layer isolate the original image from damage, but you can utilize blending modes, and opacity settings for even greater creative control.
Get Fancy with the History Brush
Apply a major change to a document (possibility a Brush Stroke filter).
Select the History palette.
Click the Create New Snapshot button to take a snapshot of the image in its current state.
Click on the original snapshot to return it back to its first-opened state.
Click in the History source box of the snapshot you created in step 3 to change the designation of the History brush.
This instructs the History brush to paint using the special filter-effect image.
Drag your mouse over the image to replace the original image with the image information contained in the selected snapshot.
Using the Art History Brush
The History Palette comes equipped with two History brushes—the History and Art History brushes. The History brush paints whatever state or snapshot is selected. The Art History brush gives you the ability to create some painted effects, using information from one or more snapshots or History states. In effect, the Art History brush gives you the power to combine image information (based on the active snapshot or history state) with artistic brush strokes.
Use the Art History Brush
Click and hold the History Brush tool on the toolbox, and then click the Art History Brush tool.
Select from the following options on the Options bar:
- Brush. Select a brush tip and style.
- Mode. Select a blending mode from the list. The blending modes, when applied to a brush, control how the colors blend with the colors in the document.
- Opacity. Enter or select a value from 1 to 100 percent.
- Style. Select a style for the Art History brush.
- Area. Enter a value from 0 to 500 pixels to define the painting area.
- Tolerance. Select a value from 0 to 100 percent. Higher values limits paint strokes to areas in the image that differ from the color used by the Art History brush. Lower values lets the Art History brush use unlimited strokes, regardless of the color values in the image.
Drag your mouse over the image, using small controlled strokes.
Changing the Eraser Tool into the History Brush
Photoshop has one more tool that works with the History palette—the Eraser tool. By changing a preference on the Options bar, you can turn the Eraser tool into a History brush. Using the Eraser tool to restore the image is just another way to get the same result as the History brush. And if you know anything about Adobe, they give you at least three ways for everything. Consider multiple ways to perform the same function as a control advantage. No two Photoshop users will create the same design, and no two Photoshop users will ever tackle a problem in the same way. Adobe gives you choices; so choose the best way to accomplish a task based on the available options. And remember, if you change the color mode, resolution, or canvas size of the active image, the History brush tools will not work.
Change the Eraser Tool into the History Brush
Select the Eraser tool on the toolbox.
Select the Erase To History check box on the Options bar.
Select a history state or snapshot from the History palette.
Drag the Eraser tool in the image.
The eraser tool does not erase the image, instead it paints the image, based on the current History selection.
Did You Know?
You can use multiple layers with the History brush. When you use any of the History brush tools, it’s a smart idea to create a new layer, and do your History painting in the new layer. That way, if you don’t like what you see, you can always delete the layer. In addition, placing the History information in a separate layer gives you the creative control of using layer transparency and blending mode settings to achieve greater creative results.