I've seen posts on various Pentax forums debating if there is a difference between the FA31mm, which is now made in Vietnam versus when they were made in Japan. As has been mentioned by several forum members, I can confirm that the same glass and components are being used and that our plant in Vietnam is "assembling" these lenses with the exact same specs as was used in Japan.
Partly to satisfy my own interest and also determine if there was potentially a noticeable difference in samples from the different countries of origin, I had our logistics manager procure for me three samples of the 31mm lens made in Japan, as well as three samples of the 31mm lens made in Vietnam. From a workmanship standpoint, I have found no discernible differences in the fit, finish or mechanics of these samples.
In my limited spare time over the past three to four months, I have put these lenses through a series of different tests shooting with both my K-7 and K-x. None of these tests were done in a lab, but I mixed up my shooting environments to include dim light, bright sun, abstract scenes, grand kids, etc. In fact, all my recent photos shot with the 31mm lens where randomly taken with the various samples.
To illustrate this post today, I've included two photos of the same flower vase shot with a Japanese 31mm and a Vietnamese 31mm. As it was raining and windy this morning when I took these photos, I wouldn't peep too deeply into these images. You're likely to see blur in the branches due to wind. However, if you sit back and just look at the overall color, contrast and saturation of these images, you'll find as I did that there's no real difference between the samples. And beside acuity, I've always regarded these attributes as the real test of any given lens.
I recognize that my post will not stem on-going discussions and debates about this lens, but I would hope this helps clarify the situation to some extent. I'd also like to point out to anyone that is relatively new to the arcane matters that surround high-quality optics, that these intense debates about the 31mm's country of origin are not new to our industry. For years, many Leica photographers have debated the merits of Leitz lenses made in Canada versus Germany. Although you can find many references to this debate, here's a link to one forum discussion Canada vs German Leitz Lenses .
So, in trying to summarize the reason for my post, I would not be overly concerned with the country of origin for any high-quality lens that you consider buying today. Based on my tests, I can't see or feel any difference between my FA31mm samples.
And to those that continue to promote widely that "made in Japan" FA 31mm's are better...you might just inadvertently end up setting higher prices for these samples on the "used", "LNIB" open market. Yes that did happen with used Leitz lenses for awhile, and I'd hate to see that happen with the 31mm since it'd be based more on myth than fact!
(As the photo above shows, I tested a range of FA31mm samples including an older "silver" version. Notice the middle lens is stamped "Made in Japan" on the lens shade ring, whereas the Vietnam made sample to the right simply has the serial number stamped in the exact same location. I compared workmanship of all components, including the lens cap. I am not sure if the photo clearly shows the comparable fit and finish of the lens caps, but I can tell you that I've already mixed up the "black" caps and really can't tell which cap goes with which lens...smile)
