The photoshop history is a beautiful thing… If anything has your back as a photo editor this is it!
I recommend going into the Photoshop Preferences and setting the number of history states up to at least 100. This is how many changes you can undo and as one click on a brush is a change it is good to have this number set to something higher then the default.
Setting this too high can impact your performance so it is wise to be cool and not just set it to something irrational.
Here is a quick breakdown of the different parts of the history palette.
The most current step is at the bottom of the list. The current image state is indicated by the blue current state indicator widget. If you click on a step that is not the last the actions after that step will be undone and they will appear greyed out. If you continue editing at this point they will be erased from the history and your current actions will be recorded.
If you have non liner history turned on you will be able to drag a single step into the trash without disturbing the rest of the list, you can set this in the palette options dialog. A good example of this is if you move a layer by accident and continue with the edit for a few minutes before you hit the OMG what happenned point.
The dark underbelly of the non-linear history is that it will always add new actions after the last step so I always have it turned off until I need to delete a non-linear step.
The History palette’s options dialog is accessed from the palettes sub-menu. This sub-menu is on the upper right corner of the dialog.
I like to set it as follows:
Automatically Create First Snapshot: ON
This will make an initial snapshot of the open state. This is very useful in comparing the current state of your edit to where you started.
Automatically Create New Snapshot When Saving: ON
Creates a new snapshot of each save. These are good place markers if you forget to make a snapshot every-so-often.
Allow Non-Linear History: OFF
Allows you to delete a history step without deleting all subsequent steps. I generally have this off except when I want to delete a step from the middle. If this is the case I turn it on and then off again.
Show New Snapshot Dialog By Default: OFF
This gives you the choice of naming snapshots or not, it will auto name the automatically generated ones and name the rest Snapshot 1 etc.
You can rename a snapshot by double clicking on the name.
Make Layer Visibility Changes Undoable: OFF
Changing layer visibility is a non-destructive change so I don’t like it in my history.
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Once you have learned the parts of the History palette you will rapidly find ways to leverage it in editing photographs.
One of my standard tactics is to make a snapshot prior to making a change that I am unsure of, make the change and another snapshot.
Then I can flip between the pre-change state and the post-change state with a single click to see if I am achieving my goal or simply making a mess of it…
Here is an action set that uses the snapshots to preview different B&W renditions using the channel mixer. This is in a zip file so you will have to unzip it prior to loading the action set.
Download B&W Renditions Action Set
Run the "CM Snaps LAB Lightness" action and then look in the history palette. You will find a set of snapshots that give you some basic different settings of the channel mixer.
By flipping through these snapshots you can rapidly determine which of the states makes the B&W conversion of your image look best.
There are 3 actions in the set, one is straight ahead RGB channel mixer settings, the next does that with the addition of a LAB Luminance layer snapshot which is diffefent from the RGB renditions and the third is the Luminance snapshot only.
I find that often adding the Luminance layer on top of a B&W conversion and adjusting the layer transparency you can add some sparkle to the highlights.
Try making snapshots as you work. You will definitely find them to be helpful but... remember to make a snapshot before selecting an older snapshot to allow you to get back to your latest edit easily.