Over the years, I have created several Shared Photo Albums. But today when moving my Photos Library to an external drive, I discovered that the photos in these shared albums are a lower resolution than the original photos. Does this mean the all the original photos with the original resolution which are in Shared Albums are lost?
MacBook Pro 15″, macOS 15.1
No. The original of a photo should still be wherever in your library it was when you added the reduced copy to a Shared Album unless you subsequently deleted the version with original resolution from your library.
If you deleted the copy with original resolution, then failed to recover it from Recently Deleted within 30 days (or explicitly deleted it again from Recently Deleted) without making a backup of some sort, then that would mean they are lost
Apple Photos Shared Albums and Photo Resolution
