Crappy focus motor quality in some lenses

On 22/04/2016 16:51, RichA wrote:
Dpreview's article was interesting. Using more than one linear motor (if the company is CHEAP and insists on using that technology) can be a real benefit, because you can half the focusing error each time you add a new motor, theoretically. But since rare earth (the motor magnet material) prices are still very high thanks to China's 95% dominance in the market, I can see why outfits like Sony only use one. Though the glue part is mystifying.

http://www.dpreview.com/news/4271118...motors?slide=6

There's a bit of a double-edge sword when it comes to China's dominance
in rare earth (neodymium in that case) markets.
I worked for a dominant producer of refined rare earth metals a long
time ago (decades). One of the issues we had was that it's a dirty
process, separation, but also dealing with thorium. We canned
investment in new production because of greenie agitation - somewhat
hysterical it was (waste containing thorium would have been buried - so
no problem). At that time, known recoverable reserves of neodymium were
in tonnes (only several). It was extremely expensive - everybody wanted
it for miniature motors etc.
The Chinese couldn't have cared less - they had the ore, there was good
money to be made, life was cheap.
Now a couple of years back, China decides that there's reason to tighten
up on environmental controls - that's bad? OK - by the time they made a
move, they dominated supply, and it would have been a nice /economic/
gesture if they'd stated "oops - we're killing people here - we'll sort
it out, eventually - if that's okay with you". However, even for a
totalitarian dictatorship, that's not a tenable position. They had to
act. They did the right thing (a couple of decades late - but anyway,
better than not doing anything at all).
Meanwhile the users of refined rare earth metals/oxides enjoyed the low
prices - and never said a word.
Don't blame China for the situation - allowing them to dominate the
market. The buyers knew exactly what was going on.