Is this a good lens? How does compare with the 180mm Zeiss Sonnar? OK so I have a Bronica system and I've been kind of wanting to get a 180mm lens but I wasn't sure if it was worth paying the price (~$800)....I figured that I might as well go Hasselblad & Zeiss. However, I found an OK deal (~$400) so now i'm seriously considering this lens. The technical specs sound great but I don't hear much discussion on this lens or see too many samples. Any opinions?