Nick,
All your suggested lens counterparts are adaptations from cameras other than the Pentax 645. I deliberately steered clear of lenses such as this, when I drew up my comparative list. I only included lenses made by Mamiya, with an M645 bayonet fitting, specifically for the M645/645AF line, and optimised for the camera's 6x4.5cm format (70mm image circle). I did exactly the same with the Pentax 645 lens line, in this case also allowing any lens made specifically for the "cropped" digital sensor. The point was to see which lenses Pentax and Mamiya/Phase produced, matching that standard definition of a lens system.
Now the inclusion of Pentax 67 lenses may seem justified on the basis of the full coupling adapter that the Pentax 645 has. One can equally use such lenses on a Mamiya, but the aperture won't be coupled (of course some of the longer P67 teles have no aperture coupling at all, even to the Pentax cameras - just a preset aperture). But that is to ignore the design parameters of those lenses - that they are optimised over a 90mm image circle, and that they deliver their desired effect on a 6x7cm output image.
So that 35mm lens you listed gives a 180-degree fisheye effect on 56 x 70 mm film. It's not much of a fisheye on a 44 x 33 mm 645D/645Z sensor: 111 degrees. The M645 24mm is not a full 180-degree fisheye on a 44 x 33 mm sensor either, but at 142 degrees it's 30% more "fishy" than the 37mm, and at 174 degrees on the 60MP and 80MP backs, it's only a few degrees short of its 180-degrees design.
And that 75mm shift lens you listed was designed for semi-wideangle architecture shots on 56 x 70 mm film. It's a short telephoto on a 44 x 33 mm 645D/645Z sensor. It's still a shift lens, but you'd have to be able to position your camera over 60% further away from the building to get the same amount of building into the field of view, and even if that is physically permitted by the surroundings of the building, it changes the whole perspective of the photo.
The 105/2.5 lens you listed is very nice, but it's not a standard lens on a 44 x 33 mm 645D/645Z sensor - it has the field of view of a classic portrait lens. Almost exactly the same as 180mm on 6x7.
There never was an official Pentax 67 500mm f4.5 lens.
Pentax made a 500mm f4.5 lens for 35mm format cameras, and at one time in the 1970s offered an adapter to the P67 mount. It can't have been well corrected outside its designed-for-35mm image circle. Also, that lens is not an APO, not even ED.
Photoshop is very good, but if you think it can replicate the unique asymmetric ray-deviating properties of a real soft-focus lens with dialed-in spherical abberation, you are mistaken. Nothing but actual optics can do that.
As for your sneering about "How's the weather in 1985?"...that's just unnecessary. Can we not keep a factual discussion factual? Either the Pentax 645 system has a compact mirror lens, or it doesn't. Fact: it doesn't. It's irrelevant whether
you like catadioptric lenses, or consider them relics of the past. I and many others happen to use them. The Mamiya's optics are a step above the 35mm-format mirrors that people may be familiar with...Jack Welch has reported on this in getdpi.
Finally, I cannot let this go without comment:
> The main difference is actually that the older Mamiya 645 lenses are most crap. Looked good for weddings on film. Just not in the game for high-res digital. The older pentax lenses are.
Have you any evidence that "the older Mamiya 645 lenses are most crap"? You realise that you lose credibility when you throw out sweeping, unsubstantiated, derogatory statements like that? Any considered research on this shows that both Mamiya and Pentax older lenses are fine, and in many cases excellent, performers on high-res digital. Quite apart from these 44 x 33mm medium format sensors, there are vast numbers of sample images and reports online by those using them on high-res 36 x 24 mm full frame cameras. Some lenses are better than others, but nobody says they're crap.
Ray
