Mac storage basics · iPhone and iPad backups and updates
How do I import photos from my iPhone straight to an external drive?
Short answer: Open Image Capture, select the connected iPhone, set Import To a folder on the external drive and import. Files arrive as ordinary photos, not in the Photos library.
Use Image Capture, which comes with macOS: connect and unlock the iPhone, open Image Capture, select the phone, choose a folder on your external drive in the Import To menu, then import selected or all items.
This copies files as ordinary photos and videos without adding them to the Photos library. If you use iCloud Photos, your pictures may already be in iCloud, and only originals actually stored on the phone can be imported.