A slightly late post, but seeking advice on moving to iCloud photos. I used to utilise photostream to move photos from my iPhone to my Mac, so have a large collection on both devices. I tried switching on iCloud photos at the time photostream was being switched off, but all it seemed to do was start copying all my photos from my Mac to the iPhone and vice-versa, generating massive duplicates on both devices, so I switched it off. Is there any way to bring them into sync without going via 100s Gb of duplicates and waiting for duplicate recognition to spot and then manually remove?