FA 31mm Limited assembled in Vietnam - bad QC or bad luck?
For the above case, it is so obvious that the Japanese made FA 31 is much better, on the same body of that Pentaxian, whom believed that the Vietnamese made FA 31 was defective and he felt particularly lucky to have a Japanese made one as the replacement, which worked.
Next, look at the shootout test below on the resolution test chart (same setup, same body (a K-7), same place and almost the same time but only different lenses):-
http://forums.dpreview.com/forums/read.asp?forum=1036&message=34477862
Or the full size images for the comparison below:-
http://www.eisner.id.au/images/Vietnam.JPG
http://www.eisner.id.au/images/Japan.JPG
(Above: Click to Download and View in a New Tab/Window)
So, what do you find out? Can you see any difference(s)? To me, the Japanese lens is actually slightly sharper and more importantly, there is less vague/mixed boundaries between the black and white, i.e., the contrasty edges (will explain and illustrate more on the problem below).
And then, Ned Bunnell tested his 3 copies of the FA 31:-
http://nedbunnell.blogspot.com/2010/02/country-of-origin-debate-over-lenses.html
Side-by-side photos of his lenses are posted. And a pair of comparison shots are also posted. In fact, I do see minor differences for both, although they are not very obvious. In fact, if you inspect them more carefully, it would not be too difficult to see the colours of the coating of the front glass elements (look at the reflections) are somehow different. And, the image rendition could be different, too - although the differences may be subtle and are not as noticeable and obvious as the coating difference.
Btw, I have made a guess at the above post of Ned's blog lately for which image is from the Japanese lens, I shall wait Ned to reveal the answer but I have some confidence that I will be correct! :-)
Besides, do note also that the 3 lenses of Ned is of late version of the FA 31, which are all with green lining inside the lens cap, against the black lining used in early Japanese production of the "same" lens.
So, after all, my own experience with the FA 31? In fact, I have not been able to find a FA 31 that is consistent and not out-focusing in AF on a K-x body, i.e., on all the K-x bodies that I have used and owned! And, the image contrasty edge "leakage" problem seems to be a real and common issue (could be with different extents, though), see my following centre crop of an image produced by a brand new Vietnamese made FA 31 out of the box below (picture taken at f/2):-
(Click to View in Original Large Size, a New Tab/Window will be opened)
With a Japanese made 35/2 prime, there is not such an issue, see (the following was taken at f/2 wide opened):-
(Click to View in Original Large Size, a New Tab/Window will be opened)
It can be noted that the above two test shots were taken at almost the same time, for the same target, at the same environment, on the same K-x body! The 35/2 shot at f/2 is obviously sharper, too, just *also* because its AF is spot on, whilst the FA 31 is indeed out-focusing!
So, what would I say? Optically, the FA 31 lens could be nice, only when it is stopped down or when it is wide opened but focus properly. The most unfortunate thing is that for such a fast, luxury and expensive lens, its AF is particularly problematic and actually no K-x body I have ever used can cope with it and the "contrast leakage" problem is another annoying issue. As for the focusing errors, most of the resolution of this supposed to be high resolution lens is wasted when it arises, unless you use LiveView to do the AF and/or to do MF with some kinds of aids.
In fact, as one of the my Blog readers who just posted here yesterday have pointed out, it is quite obvious that Pentax/Hoya actually somehow feel ashamed of the lenses and camera bodies are being made outside Japan. If not, they should have printed "Made in Vietnam" and "Made in Philippines" instead of the wording of "Assembled in" against what they do with the "Made in Japan" labels over decades, which is undoubtedly they were being much proud of.
Blog Trailer: To show how the workmanship and (quality of) the materials could be really different for the early Japanese production Limited lenses against the late Japanese/Vietnamese production of the "same" lens, I shall take some macro shots under a bright light source to show you the real and existent differences I discovered. (.. as some people just can't believe. So, I will just show them some evidence! :-))
[ Update 4-7: Done! Continued in the Next Part, Here.. ]
All Related Blog Posts on This Topic:-
http://ricehigh.blogspot.com/search?q=vietnam