That's what I thought myself, but then I realized pictures put into shared albums are actually copied - you can delete the original and it's still available in

That's what I thought myself, but then I realized pictures put into shared albums are actually copied - you can delete the original and it's still available in the shared album, at 0 cost to your iCloud storage. It's kind of a nice feature, but at the same time it makes doing things like collecting photos from my wife for a photo book annoying.