I assume I could export the remaining, non-duplicate media from Photos and retain meta data. However, after removing all the duplicates from the Photos Library, I could safely delete the original folders.

I assume I would end up with yet another copy in the temporary Library. I’m not sure how to proceed using a normal Photos Library. I thought if I deleted the duplicates from Photos, the files would automatically be deleted from the external HD. I was planning to use Library referenced media. I would import all the collected media into the new Photos Library. My plan is to make a temporary Photos Library (but not a System Library) on the external drive. The folders for these all media reside on an external HD. O exported media and media copied from Photos on existing Macs, iPhones and iPads o extractions from archives made when old Apple devices were replaced with new devices o extractions from numerous OS X iPhotos/Photos Folders that were archived o extractions from numerous Time Machine backups o a large number of media that I know are not duplicates My media are in a large number of folders and fall into these categories. I plan to make a separate Photos Library on an external drive.

The application is slow and cumbersome to use. I used a third-party stand-alone OS X application to start this project, so I know there can as many as 6 identical copies of some media. I want to delete the duplicates completely from my HD. I know Photos can find and merge duplicate images and videos (the media).

Remove duplicates from apple photos