I have been using the Mamiya 28 mm on my ZD and am overall happy about the lens.
- sharp, it should be able to tap into the resolution potential of the P45 accross most of the frame (the very corners are a bit soft on the ZD even at f14),
- very little distorsion,
- Flare is OK, but it can obviously not compete against LF Schneider lenses for instance.
On the downside:
- heavy
- dark and difficult to focus in low light,
- difficult, or perhaps even impossible, to use PL filters,
- front element likely to get damaged quickly because of its shape.
It is a very expensive piece of glass though.
Regards,
Bernard