Okay folks, quick report for you:
I am in a Starbucks waiting for a meeting, so no time to upload photos, but I shot a basic landscape image today with both lenses, all apertures, all from the same spot. While that is not a complete "test" I can at least give you my first impression. And that is my copy of the Mamiya 35 and the new Phase lens are essentially IDENTICAL in performance, at all apertures, corner to corner. IOW, the new lens matches my copy, which was one of the best I ever shot with. That's the good news. The bad news is the best 35 is not what I'd call a stellar lens. It is a good lens, but needs to be stopped down to f11 to get usable corners on FF. F16 starts to show diffraction, and I'd call the added DOF about a wash with the loss of central clarity from diffraction. Obviously f22 is worse. F5.6 is good centrally, but softens up about 2/3 out. F8 is better, softening up about 90% out. Either would probably be fine on a P40+ crop at the corners.
When I say good centrally I mean good, not excellent. This lens is simply not quite as crisp and has lower contrast than the longer primes. In fact, the 28 is sharper with more contrast centrally than the 35; the 45D even more so. However for most landscape type scenes, with a little contrast and clarity boost in the raw processor, and maybe a bit harder capture sharpening, the 35 holds up very well corner to corner at 24x32 print size. It's also a lot smaller than the 28, and even a bit shorter than the 45D. What that means for me is it's always in the bag when I need it -- I could not say that for the 28.
I will shoot some more images with it tomorrow and Sunday and then get it back to Paul on Monday. So, if anybody wants a confirmed "as good as it gets" copy of this lens, contact Paul at Optechs ASAP!
Cheers,