In the iOS 16 Photos app, both the "Hidden" and "Recently Deleted" albums under Utilities are locked with Face ID or Touch ID and cannot be opened without biometric authentication or a passcode.
In iOS 16, your iPhone will automatically detect any duplicate images that you have in your Photos app. Duplicate photos will show up in a "Duplicates" album under Utilities in Photos, giving you the opportunity to merge them to save space and reduce clutter.
If you have multiple photos that you want to edit in the same way, or if you've made changes to one photo that you want to replicate in another photo, you can use the new copy and paste edits tools in iOS 16.
To streamline photo editing, iOS 16 adds simple undo and redo buttons, a feature missing in prior versions of iOS. With the undo and redo buttons, you can remove edits that you've made to photos one by one rather than having to cancel all of the edits by reverting an image entirely.
In a small but meaningful change, Apple added an option to sort the dedicated People album by name in iOS 16. You can open up the People album and tap on the two arrow keys to change the sorting from "Custom Order" to "Name." Opting for Name rearranges the people in the album into alphabetical order.
iOS 16 adds an iCloud Shared Photo Library that's basically identical to the standard iCloud Photo Library, but shareable with up to five other people.
Though not strictly a Photos app feature, lift subject from background is one of the most fun random additions to iOS 16 as it's a little bit like a mini version of Photoshop. You can use it to pull the subject out of any image or photo