Hi Chris, see below:

Chris Eastwood wrote:

> >  I was commenting on the electrical stuff inside, the
> >AF and IS systems.  Actually we are expecting **more** like IS and AF
> >and then complaining when these newly complicated systems fail us.
> 
> actually, its not so much the IS motors, and USM motors (as I'm of the
> belief that they're reasonably robust) its more the cams and mechanical
> operation in the zooms

It is my experience (primarily with the AF system failure) and the
experiences that I have read most often from others (mostly IS), that it
is the electrical stuff in the 28-135 that fails, not the zoom system or
mechanical stuff (not that the electrical stuff isn't mechanical...you
know what I mean).  Other lenses are probably a different story, but I
have had one of these babies that took a good knock and gave up
autofocusing one direction (it would AF out, but not back in).  Many
other folks I have heard have had problems with the IS flaking out, and
actually I have had instances of this too, with this lens without any
real damage to the lens causing it (funny shuttering of the IS and goofy
noises from it).  However, note that this is the *only* EF lens I have
had any problems with either the AF or the IS, and I have had a number
of them (mostly L series, though I do have a 50/1.8 mkI which I *love*).
 This is why I cautioned the original poster specifically about this
extremely versatile, but not all that durable zoom.

I would say that pretty much all zooms, even the "solid" old metal ones,
have their problems and stop working smoothly when whacked right. 
*Maybe* it is even possible that the plastics of the new lenses can take
more abuse than the old metal cams without becoming "sticky" or "stiff".
 Not sure about this though.  Same goes for old focusing helicals on
primes, but other than the general looseness and a feeling of low
quality in today's zooms, I haven't seen a whole lot of problems with
the mechanisms.

Mike


-- 
Michael Shupe
M.J.Shupe Photography
Michigan Tech University
www.northernlightsgallery.com
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