Hi, Steven,
I was in a similar position earlier this year, and took the plunge into digital medium format.
As I'm sure you've guessed, there's good and there's bad.
First the good:
* At least with the MF back I purchased, the resolution is positively astounding. I love to print very large, and I'm now printing sizes that I've dreamt about for more than a decade (For example, this weekend I am working on framing a piece that is printed at 48" x 144". It's a 4-image stitch at 150Mpxls.)
* Beyond resolving power, there is a 'clarity' to the images that my Hassy 500C/M, Zeiss CF lenses and P45 are delivering that just wasn't present in my small format 1-series kit, even with my 300/2.8 IS, which is one of the most magnificent optics I've had the pleasure of using. I saw the very same performance from Hassy's CF39 back as well when I evaluated it.
In short, with the right glass, the image quality of MFDB's is all that and a bag of chips. I think if you do your research to hunt down the back that best meets your needs, I am certain you'll be getting the image quality you are looking for.
Now for the bad news:
That image quality doesn't come for free--and I'm not just referring to the exorbitant pricing of the digital backs--just about *everything* else suffers as well (keep in mind I'm on a Hassy 500C/M at least until I can see how the Hy6 shapes up in the real world).
Handling is poorer, everything is optimized for studio or fair-weather shooting (I shoot nature photography, and inclement weather is often a superb time to go out shooting), performance is slower, AF is slow or non-existent, the body is bigger, heavier and boxier and battery life is poorer.
So if I haven't scared you away yet, then medium format might be for you!
Knowing what I know now, would I do it again? The answer is 'yes', I would, in a heartbeat. Despite the limitations of the format, I'm getting exactly the results I was going for. If small format could deliver comparable results to medium format, then I might be tempted to go back, but it doesn't. Even the 1DsMkIII doesn't come close to the image quality that medium format is delivering. I'm not even sure it is fair to compare the 'convenience' of small format to that of medium format, since the small format system isn't delivering the same quality. It's a bit like comparing a point-and-shoot to a 35mm SLR for convenience--why bother, since you can't get the same results with a point-and-shoot?
Further, the MF world is a bit of a mess, to put it politely. I can't be all that sure that whichever horse I picked in this race would be around in a few years. Would there be anyone left standing in a few years? I wasn't sure (and still am not), but I wasn't going to get big, sharp prints by standing on the sidelines.
Here is what I found during my research. Keep in mind that I considered this move for four years, and spent 6 months researching it. I hope I won't offend anyone's sensibilities, but in the end these are the conclusions I reached.
Backs:
I made this expensive change to get the highest resolution possible, so I only considered the highest resolution backs available. I ruled out scanning backs because they weren't instant and most require tethering.
The current crop of 33Mpxl backs have a resolution disadvantage of about 5.6% to the 39-megapixel backs. That's not enough of a drop to be a deal-breaker, but given the magnitude of this investment, all else being equal, I was definitely interested in that extra 6%. The 33-megapixel backs started off a half-step behind in my mind for this reason.
Leaf Aptus 75 - 33Mpxl:
* pros: gorgeous large 6x7cm screen
highest frame rate available (~1fps--not great compared to small format)
* cons: I observed pretty significantly higher noise relative to Phase and Hassy at ISO 100+
Lingering centerfold issues, even after some have claimed them to be resolved.
Sinar eVolution 75 - 33pxl:
* pros: Thierry's support. He is an incredible asset to Sinar.
Multishot version available.
Swappable mounts (user swappable).
* cons: Couldn't get local support. I was unable to get even a raw file from this back to evaluate from Thierry, Sinar, my "local" Sinar rep (in San Francisco) or the US distributor. No local dealers had seen or used these backs. I'd expect this if I was based out of the Himalayas or something, but not in Seattle.
Multishot units have no screen. A deal-breaker.
Multishot units must be tethered. More weight in the field. *highly* undesirable.
Hasselblad CF39/CF39-MS:
* pros: Excellent support from local rep - Victor Naranjan
Stupendous clarity and resolution from multishot back.
Multishot back has a screen
Incredible discounts available
Only vendor with a modern, complete, digital MF package availabe now.
* cons: H-series use Fuji glass, whose rendering I am not a fan of (find they can be somewhat harsh and unflattering).
H1/H2/H3 systems are 645--no possibility to go larger (6x6) in the future on these systems
Have frequently 'broken' the system, moving from V to H, and again from H2 to H3.
With the H3 and beyond cameras Hassy has become very aggressive with respect to ineroperability
Multishot requires tethering.
Phase P45+:
* pros: Superb image quality, second only to CF39MS, IMO
Best long-exposure and high-ISO performance (still not all that good compared to SF, though)
Available for most every camera mount.
* cons: Mount change requires trip back to factory
In the end, Hassy's tactics actively preventing H2 users from using the HCD 28mm lenses, and the 'closed-ness' of the H3D didn't sit well with me. Even using the back on a view camera required me to be tethered for power or purchase a $2000 hard disk with batteries left me with the distinct impression that they weren't interested in designing the best possible solutions for me. I may still end up there, but for now, Hassy is a distant 2nd place for me.
Starting with the front of the camera, I knew that I was most interested in Schneider, Rodenstock or Zeiss glass. And I wanted a modern system. That quickly whittled me down to the out-of-production Hassy V system, the relatively modern (for MF) Contax, or the forthcoming Hy6.
A friend gave me his Hasselblad 500C/M system on extended loan, and this allowed me to go with the Hassy V for now. The optics are superb. The handling is not. But I'll stay with this for a year until I can get a chance to evaluate the Hy6 and which backs will function fully with it. Time will tell.
Until then, I'm very happy with the results I'm getting on the Hassy V system. I did shoot a reception using my small format gear, but aside from that, haven't used the small format gear since June.
Hope that helps at least a bit. Feel free to contact me offline if you wish as well--I'm happy to help out however I can.
Best regards,
Brad
Also, FYI, your homepage isn't listed in your profile.