[On August 6, 2007, Hoya completed a friendly public
tender offer for Pentax and acquired 90.59% of the company.
[8] On August 14, 2007, the company became a consolidated subsidiary of Hoya. On October 29, 2007, Hoya and Pentax announced that Pentax would merge with and into Hoya effective on March 31, 2008.
[9] Hoya closed the Pentax-owned factory in Tokyo, and moved most of their operations to Southeast Asia. All professional (DA*) and consumer (DA, D-FA) lenses are produced in
Vietnam, whereas DSLR cameras are produced in
Philippines. ]
This article was copy-pasted from he Wikipedia website. Now I'm not sure how much skill it takes to put those lenses together. I'm sure that the technicians who use to put those lenses together did not all pack their bags and move to Vietnam. It must have taken a certain amount of training to get the new workers up to speed. I'm pretty sure some expertise might have been lost during that transfer of operations, but how much did it affect the build quality of certain lenses, probably only Pentax and Hoya know for sure ?
So far, I have not had any issues with lenses made in Vietnam or with my K-5 II which was built in the Philippines.