Wow, interesting. I'd been under the false impression that the full backup used an internal snapshot to capture the state of the database at the time the backup started. I'm intrigued that that is not the case, and changes to pages made after the backup has read the page are captured from the log at the end of the backup process. This seems a bit awkward to me, as it makes the point in time of the backup a bit fuzzy depending on how long it takes to process.