Hi This is in German. What I could translate is the 28 mm is f 4.5 and will work with film backs ( 28mm, the same as a 17mm on a 35 format ). On the ZD it is 32mm ( 20mm on 35 format). With a Leaf back it would be the 32mm ( Aptus 22 & 33 ). They also have the Zd back, seems to have the same specs as my ZD camera. Plus they have a RAID system for the studio.