I promised a quick report on the Mamiya L 65mm f/4...
It's early days with the lens I chose for 65mm -- the Mamiya L 65mm f/4 -- but so far I'm very happy with the choice. Bill Rogers from Mamiya Repair in Nevada locked the shutter open and removed all the extraneous bits I don't need.
My plan was to replace the Mamiya 7 lens mount with a Mamiya 645 mount I scavenged from an extension tube set. I already built the Mamiya 645 recessed lens board for my Arca-Swiss F-Universalis while I was waiting for the lens. It turns out that Mamiya re-used the basic design of the Mamiya 645 mount. A Mamiya 7 lens with all the electronic bits and levers removed will fit nicely on a Mamiya 645 extension tube mount with all its extra bits removed. The mount designs are not exactly the same, so the Mamiya 7 lens sits a bit loosely unless the springs in the mount are tightened. That was quick and easy, so now the lens mounts snugly.
Public Service Announcement: Please don't try to put an unmodified Mamiya 7 lens on a Mamiya 645 camera. You'll wreck one or both!
Best of all, this copy has a buttery smooth focus ring. The older Mamiya G lenses I use have stiff focus rings due to dried grease, which doesn't bother me because I only use them on digital view cameras where I focus by rail. I was hoping the 65/4 would have a good focus ring because I was looking forward to making a direct-to-GFX mount for it.
That mount project took a bit longer, but also worked out well. The combination of the GFX to M65 adapter, M65 helicoid and Mamiya 645 mount from an extension tube come just shy of the exact length needed for infinity focus. I'd rather be under than over, so this is ideal. Plus I now have a close focusing Mamiya 7 65/4. With its own helicoid, it only focuses down to around 1 meter, but with a bit of extension from the M65 helicoid when needed, I can focus to around 30 cm.
I won't comment much here on image quality because it's early days. I need to use a lens a lot before I feel confident about image quality. I can say that so far it seems excellent and I'm not seeing anything I didn't expect. For instance, the published MTF data gave me a head's up that the centre would be excellent at f/4, and the edges a bit soft, but by f/8 it would be excellent across the GFX frame. And that's exactly the case. I was also expecting 20mm of good quality shift in landscape because the lens was designed for 6x7 film, and that too is the case.
Mamiya L 65mm f/4. Top is on a direct-to-GFX adapter, and bottom is on an Arca-Swiss F-Universalis. Both adapters use a custom Mamiya 645 mount (which is an almost perfect fit for a 'stripped down' Mamiya 7 lens).