I have about 58,000 photos/videos (~1TB) catalog in Lightroom 5. These photos/videos are stored on an external USB drive.
Since I'm using a very old version of Lightroom, I'm considering moving to Apple Photos (Mojave 10.14.5). I've moved the Photos Library to a folder on the external drive, which has about 530GB of free space. When I tried to import, Photos complains "Insufficient Disk Space. Additional 760.47 GB of free space is needed to continue." In Photos, I've unchecked "Copy items to the Photos Library". Why does Photos need this much space? I'd like to keep all the photos exactly where they are.