What happens after IMG_9999?

Photos is using internally unique, very long filenames for all images, something like 3A1BA9C9-6B2C-4F5C-BCAC-B69D58B7CB56.heic

Only when we share the photo, the filename created by the camera will be restored. For exported files the filename may create problems, when you export two files with the same name to the same folder in the same export session, but that is unlikely to happen.

Well, I filed a bug report after the duplicate detection marked my photos with similar filenames as duplicates. Perhaps Apple has fixed it since then. 😀

It has been frightening, because it has been hard to notice.

For example: These five duplicate candidates have been shown with the same thumbnails, look alike:

You can see, that the files are different because of the different file sizes, but all filenames were identical.

When I clicked one of the look-alike thumbnails, to view it enlarged, I could see, that the image has been a very different image.

I might have lost quite a few photos, if I had not looked closely at each suggested duplicate.

Old Toad wrote:

They are not duplicates due to the EXIF creation date difference. Photos has no problem with identical file names because creations dates will be different.

That I what I expected to happen, OT, but when I first looked at the Duplicates album in Photos, in the early version of Monterey, I found some images listed as duplicates, where only the filenames have been identical, but the content completely different and the capture date slightly different.

That is one reason, why I am always checking the entries in the Duplicates album, if they are really duplicates before merging them.

They are not duplicates due to the EXIF creation date difference. Photos has no problem with identical file names because creations dates will be different.