iPhoto automatically saves changes to photos, albums, slideshows, and projects (books, cards, and calendars) as you work, so there’s no Save command. You can undo some or all of the changes you made to a photo at any time.
To undo the last changes you made:
While still in edit view, do any of the following:
Click the Undo button.
Choose Edit > Undo.
You can repeat this step multiple times, to undo your last several changes.
To undo all changes made during an editing session:
While still in edit view, do either of the following:
Click the “Revert to Previous” button.
Choose Photos > “Revert to Previous.”
If the button or the command says “Revert to Original,” it means this is the first time you’ve edited this photo.
To revert to the original photo:
Select the photo.
Do one of the following:
Choose Photos > “Revert to Original.” (If you are in full-screen view, move the pointer to the top of the window to make the menu bar appear.)
In the Quick Fixes tab of the Edit pane, click “Revert to Original.” If you don’t see the “Revert to Original” button, click “Revert to Previous” until the button changes to “Revert to Original.”
To revert to an original RAW-format photo:
Select the photo, and then choose Photos > Reprocess RAW.