I did not say that problems are frequent. What I can say that it can happen to any lens. I have seen at reports on at least two Hasselblad lenses, for instance, not counting the one that fell apart for Michael Reichman in Namibia. James Russel had major focusing error on one of his Leica lenses, as far as I can recall. S**t happens.
Look at the enclosed figure from Lens Rentals it has Imatest MTF plots of I guess around 50 lenses. There is a lot of variation. The Zeiss lenses may vary a bit less than the others. Of the 50 lenses one stands out, which is clearly a lemon. If you happen have that lemon lens it would better replaced.
For my part, I have or have had about 50 lenses, and two of those were obvious lemons. One I got immediately replaced the other I sent back just before warranty expired. The second lens was not fixed. It is well possible that other lenses were lemons, without me taking notice. But my experience is mostly with 135 lenses, of MF lenses I have only five and all MF lenses were used with film.
I'm fully aware the you (Anders) find that Joseph Holmes article on problems encountered on MF equipment is irrelevant, but you have never explained why
. The article is here: http://www.josephholmes.com/news-medformatprecision.html
He found for instance that five out of twelve Phase One backs were out of focus. Mark Dubovoy has had four Phase One backs and half of them was out of focus.
The article has a long list of lens samples and I guess that more than half has issues. I guess it depends on Mr. Holmes and Mr. Dubovoy being meticulous, but still I think the information is relevant.
Some of the findings: "I take that as approximately a one-in-four chance of getting a good superwide, view-camera-type, German lens when you order one. And for every lens that gets rejected by one photographer, if the thing isn't made right by Schneider or Linos/Rodenstock or one of the other vendors who assemble elements to shutters (possibly including Linhof, Sinar, Horseman, and Cambo), it then just serves to reduce the chances of getting a good one for the other photographers to almost zero. And these things aren't exactly in great supply to begin with."
"Linos and Schneider -- get your act together!!! Make sure every lens shipped comes at least quite close to the MTF specs you yourselves have computed and in many cases published, if not guaranteed. If anyone on Earth is capable of superior quality control, surely your two companies are.
And Phase One -- you too! Make sure every back shipped is within your own 12 micron focus calibration standard. And that should include the loaner backs you give people.
Photographers -- expect trouble and look for it. Make wide aperture test shots at infinity and examine the results. Check to see that all four corners and the middle are sharp, and more or less equally so. Expect to have trouble focussing your M.F. digital cameras -- simply because the precision required is so extreme. [I intend to write an article on a great method for facilitating accurate manual focus of the Mamiya and Hassy H bodies soon, in early April, 2009.]"
Finally, Joseph Holmes found a good P45+ back and a few good lenses and was much satisfied with the results. My understanding was that he and Charlie (Cramer?) went with Mamiya lenses.
Some other photographers also commented on Mr. Holmes article: http://www.josephholmes.com/news-fellowphotographers.html
Very much possible that the situation improved since 2009. Still I would suggest that it is a very good idea to test every piece of equipment.
Not quite Erik. It is in general different than for DSLR where there seem to be much more sample variations. Mamiya 645 is a relatively old system and when Phase One stepped in there was a mixed bag of lenses. Some were very good and some were not quite. The older MF lenses more so a mixed bag. The Mamiya D lenses were introduced after Phase One stepped in. Per what I understand they are given a better quality control than the other AF lenses, which among some are still very good lenses. Apparent there are some sample variation on the AF lenses, and also MF. Here is an overview of Mamiya lenses http://forum.getdpi.com/forum/lens-accessory-reviews/15710-mamiya-lens-overview.html
For other medium format brands such as the latest Rolleiflex lenses I have not heard of any bad copies yet - zip zero period. I believe it bottoms down to design and quality control. Also frank cultural since I experience made in Germany more reliable than made in Japan, regrettably. Medium format is servicing a higher end which should (and most time do) mean stricter requirements, and likewise also smaller series of fabrication. Hence they should undergo stricter quality procedures. If a lens is not acceptable it should be sent back for adjustment to perfect - within tolerance preferably. Regrettably, for service I have not experienced Mamiya Japan very good to deal with... which was part of reasons I gave up on Mamiya 645 system. My 45mm D went back to them two times, although it is a very sharp lens I would recommend.
Above said, my favorite Mamiya 645 lens was not the sharpest, the 80/1.9 N lens which was manual focus, very shallow DOF and an impressive low weight. It simply had a very nice character, though not as silky smooth as the Hassy 110/2 or Rolleiflex equals of f/2. The 80/1.9 was the last lens I sold off from my Mamiya 645 collection when I switched to Rolleiflex Hy6 system, the 45mm D was the second last...