I am considering to use iCloud Photo Library to store a growing number of family photo albums, shared to web or set of AppleIDs.
I dont need to keep original photos on iDevices for 99.9% of photos.
How much space will be used on the photo-originating set of devices (iOS, OS X, Windows)? I.e. what (roughly) is the function from the original size and number of photos, device storage space available, any other variables?