--- Skip <[EMAIL PROTECTED]> wrote:
> John Chennavasin wrote:
> > On Wed, 21 Feb 2001, Rome wrote:
> >
> > > I'm new to Canon:
> > > Are the USM lenses just quieter or are they
> > > actually better than non-USM lenses. By better,
> > > I mean optically better, or faster focussing.
> > > I don't give a hoot about noise.
<big snip>
> As an addendum, most, if not all, micro USM lenses
> have rotating front elements, ring USM lenses have
> stationary front elements. This makes it easier
> to use filters that require orientation, like
> polarizers and gradients.
Skip,
Make that most. There's always at least one exception
to every rule (I think they taught that in first grade
English!).
The 50 1.4 USM has micro motor USM but its front
element doesn't rotate. It does however use the front
element(s) to focus, so the front of the lens while
not rotating, moves in and out during focusing.
It's also the only lens that breaks the rule about
micro motor lenses not having full time manual
focusing :-)
Regards
Gary
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