I forgot to mention that I'm doing long exposure (2-10 minute) black and white landscape photography.
2-10 minutes massively cuts down your options in MFD. You're left with a Phase One P20+, P21+, P25+, P30+, or P45+ back (on the camera of your choice); or a Pentax 645D. The Pentax 645D has the best and most recent sensor of these. The P30+ and P45+ are the next best. The P25+ and P45+ have a slightly larger sensor, which keeps wideangles wider.
AVOID any Mamiya with a "DMxx" or "DLxx" name. That means it has a Leaf back, which means a Dalsa CCD, which means it cannot do long exposures of the sort you want. The other Phase One backs I didn't mention (P40+, P65+, and all the latest IQ1xx series) all have the same problem. AVOID.
As bodies go, there's nothing wrong with a Mamiya 645AFD; it's what I have. That is, some folks don't like
any of the Mamiya AFD/DF line; but within that line, there's really not much separating the 4 incremental versions of the bodies. If you like one, you are amenable to them all. You're a Canon man, and the things that some people bemoan in the Mamiya tend to be the same in a Canon (tiny buttons and menus etc.); in fact the trend to "Canonisation" increased as the series developed, so you'll find the most mechanical levers and switches on the oldest AFD, while the newer AFDIII and DF are the most reliant on tiny buttons. And BTW, a 645AFD body should not cost more than about $500; $650 with film back; $900 complete with 80mm AF lens and back.
If you don't need AF for all your lenses, Mamiya is the best way to go, as there are tonnes of very inexpensive, very fast, and very unusual (fisheye, shift, soft focus, macro, mirror, zoom, tilt-shift bellows) manual focus M645 lenses out there, and most other makes of medium format SLR lenses can be adapted onto it. I think this info could be important to you, as you are clearly aiming at the sub-$10k end of the market.
If your lens tastes are more classic and less specialist, there are Zeiss lenses for the Hasselblad 500 series and the Contax 645, and these will take a Phase One back no problem. They also have the option of using a waist-level finder - the Mamiya and Pentax don't. But here are a few caveats. Everything by Contax seems to cost 2-3 times more than everything by Mamiya and Pentax, and Contax are long out of business. Because of the greater crop factor, wideangles are more limited on the Hasselblad 500's. And you need an autofocusing body (Mamiya, Contax, Hasselblad H, Rollei 6008AF) to get focus confirmation with manual focus lenses; focusing a Hasselblad 500 with the precision demanded by a high-megapixel digital back is said by some to be tricky.
So you'll have to weigh things up along the lines of:
- The Pentax has the most desirable sensor, and the best value for money digital package, but does it have the range of lenses you want?
- The Contax has the most desirable body, and some standout lenses, but does it have the range of lenses you want, and can you afford them?
- The Mamiya has the largest and most affordable range of lenses, and a 645AFD is so inexpensive that a backup body is no issue, but how do you feel about the body?
- The old Hasselblads have the most classic look and feel, but the widest rectilinear lens on film will only be a modest wideangle on cropped digital, and is nailing focus with wider apertures a critical feature of your work?
Ray