Couple thoughts on Mamiya MF lenses:
LF lenses that can throw an image circle out to cover an 8 x 10" or 4 x 5" sheet of film and provide enough extra margin to allow for shifts, swings, and tilts, are necessarily going to have inherently larger circles of confusion than smaller formats, even with reduced maximum apertures. This is simply a matter of optical physics, material development, and manufacturing processes. I came to see this, studying images created with the vaunted Schneider APO Symmar 150mm ƒ5.6, that has a noticeably larger circle of confusion compared to Mamiya MF glass of equal focal length.
I had decided for my own work, to standardize on the 6 x 9/120 format, so was considering a technical camera, fitted with a 120 film back and a 150mm lens as the primary (just personal preference) optic. Closely examining some prints and negatives made using the APO Symmar left the impression one could make technically improved images by using a 6 x 9 system with optics specifically designed for the format. LF images inherently appear superior as a function of negative size, rather than lens quality itself. If you examine 35mm vs 8 x 10" pinhole camera this becomes apparent, though a worker may choose to apply the difference for aesthetic effect.
As observed before on this thread and others, Mamiya has made some of the finest MF glass anyone could ask for; even the uncoated optics of the first-generation RB67 lenses were great to start with, ultimately becoming phenomenal (I’d happily compare their quality & performance to any German glass) and I came to find the Mamiya Press lenses, specifically designed for the 69 format and platform are noticeably superior in their technical image rendering than any general purpose LF lens. I say this with a nod to the superb Tessar designs of the older folding cameras, who captured light in a far different manner, resulting in exquisite images all their own.
Who cares? Probably the medium format aficion who can’t afford a Rollei or Hasselblad system, or wants to move on from 6 x 6—never a favorite for my own work—seeking a higher level of technical excellence in their output without having to sell body parts to acquire the necessary means. Ever price a good MF digital back?
One might ask why not a specimen of the Fuji G690 (AKA Texas Leica) family? I considered that system as well but found the Fuji glass was designed with image sharpness/minimal circle of confusion as its primary goal, with color rendering a second item in the process. One the one hand, these lenses render image details blisteringly sharp, and as documentary cameras, they are second to none. From a subjective standpoint, to my eye, the images these series of cameras produce fall short aesthetically in that, they have little apparent depth. The images print quite flat: photographs made with Fuji G90 rangefinders appear to have been taken of another photograph or some two-dimensional source, ultimately resembling photographs printed in a periodical.
The Mamiya Press and especially RB67 lenses, render wonderfully “rounded” images with great depth—regardless of the aperture chosen by the photographer or focal length. Mamiya’s lens designs, IMHO, represented the pinnacle of accomplishment for task-specific MF camera systems, as the dominance of analog photography began its decline.
Pentax’s 6 x 7 system glass is a close second in my darkroom printing experience and I retain great fondness for the camera system.
Frankly, the Zeiss lenses on Hasselblad, et. al. prioritized a high modulus of transfer function to the extent that, while superb of course, fall a tad short of the Mamiya designs. Personally, I can’t justify the enormous expense for the systems seen on eBay and other used equipment outlets.
But then, I don’t care for 6 x 6, so there.
Hope these thoughts such as they are, prove useful at a minimum to assist a reader seeking to avoid the onset of ennui during an extended bathroom break… Happy trails!