Like Photoshop, – Lightroom has a History functionality that shows you a list of adjustments you have made. The History panel can be used to revert back changes that you have made to a photo. But unlike the Photoshop history, Lightroom history entries don’t purge when you close Lightroom all adjustments and fixes made remain and re-appear once you launch Lightroom next time.
The History panel is located on the left side when you go to the Develop module. History entries are logged by time decreasing order meaning from bottom to top so that the topmost history entry is your latest adjustment. What is really useful is that these History settings not only show the settings you used but also the value of the sliders and the amount of change you made for every adjustment.
You can get back to changes you made to the photo by clicking any of the entries in the History panel. You can click from one history entry to the next to view the photo at that point in the editing process.
If you click to view a photo at an earlier stage of its editing and then start making changes to the image you will lose all the remaining history states – they’ll be replaced by your new edits (similar to Photoshop).
You can delete the History
You can delete the Lightroom history for any selected photo. To do so, click the X (Clear All) button in the top right of the History panel. This removes the history steps from the History panel – this however does not remove the edits from the image – it just clears the History panel.
You can set the Before photo
The backslash key (\) in the Develop module is used to compare the photo (Before and After your edits). However, sometimes you need to set a milestone in your edit process, say after correcting exposure, you want to apply local adjustments. You want to make this point in time the new before state – not as it was when you imported it.
To do this, right click the History step that shows the image at the point you want to make the Before image and choose "Copy History Step Settings to Before". Now, when you press the Backslash key you will compare the current state of the photo with the selected history state.
You can create a Snapshot of History
Snapshots panel tends to go unnoticed by many Lightroom users, but I find it an incredibly useful feature. A “snapshot” is a version of your photo that you like and want to revert back to later on. After making a snapshot of your photo, you can continue experimenting with different develop settings, knowing that you can always go back to the version you liked.
Snapshots are not physical copies of your photos. All Lightroom features are non-destructive including Snapshots.
The first snapshot by default is your import state of the photo i.e. when you first brought it into Lightroom.
Making additional snapshots couldn't be easier. Once you've made some changes to photo, simply click the plus sign (+) at the top of the Snapshots panel. The keyboard shortcut to create a new snapshot is Cmd/Ctrl+N. From the History panel also you can get back to a History state of the photo and right click then select "Create Snapshot. So easy...