My digital shooting is with a Nikon, so Mirex does not make an adapter for the 645 lenses, but they do make one for the 67 lenses. So far I have the 45mm, 55mm (second version), 165mm f/2.8 and the 200mm. Although I am shooting with a cropped sensor, D7000, I plan on getting a full frame body at some point - unless the 645D prices keep falling.
The Mirex adapter is very nicely made. I used to shoot Canon and had the 90mm Tilt Shift (T/S) - which was beautiful, but honestly the ability to use so many lenses (relatively inexpensive) with one adapter (somewhat expensive) make the Mirex a nice option. For the price of a new 90mm T/S I picked up a used Mirex adapter and four Pentax 6x7 lenses (and have a bit of change left over to pay for part of a 6x7 100mm f/4 macro).
I also happened upon a Zoerk (Zork in the USA) Multi Focus System adapter for Nikon F mount - so I have been looking into enlarger lens options for this, but only have an older Nikkor 50mm 2.8. The really nice thins about this system is that I can purchase a Pentax 6x7 mount or Pentax 645 mount and use this setup on those bodies. Meant for close up work, but the tilting ability is really nice. Zoerk also makes a shift adapter for Pentax 6x7 onto a Pentax 645 body - which I also picked up for some architectural shooting - now that I have some wide 6x7 glass.
---------- Post added 08-15-2014 at 10:14 AM ----------
consider some of the 645 telephoto lenses with the Mirex as well... the effect of the 6x7 165mm f/2.8 with the Mirex adapter is quite nice.
Originally posted by greatgable It was the focal lengths which appealed. I could get for the price of one tse 24mm I could have equivalents to 28mm (my usual landscape length), 35mm and 50 mm