on 11/17/04 12:15 PM, John A. Lind at jlind@xxxxxxxxxxxx wrote:
> Nearly all zoom lenses are internal focusing;
> haven't seen one yet that isn't, but it doesn't mean someone, somewhere, at
> some time hasn't made an external helical focusing zoom.
>
> -- John Lind
Many zoom lenses I've seen focus by extending the front element or group
from the rest of the lens body. Although different than the prime lenses
focusing method (at least for most SLR lenses of recent design) I never
considered this 'internal' focusing... I guess my expectation is that
internal focusing moves lenses inside the works without the exterior
changing dimensions at all. I think some IF Zuiko's work in that fashion,
though off hand I can only recall that the 180/2.0 and 250/2.0 are IF, not
sure about the 350/2.8. I'm sure someone on this list has personal
experience and can report. I don't believe I have any IF lenses, at least
not for OM.
--
Jim Brokaw
OM-'s of all sorts, and no OM-oney...
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