Hi Dan,
It's for when you need to focus all the way to eternity <g>
Seriously, some Zuikos have this too, notably the 300.4.5. And my 100 f/2.
It allows the photographer to correct for changes in the lens geometry (or
whatever) caused by physical expansion / contraction of lens parts due to
being warmer or colder than the design operating temperature provides for.
Probably for a similar reason the top-of-the-line big lenses have a white
outside coat, to reduce heating under the sun. White absorbs less heat than
black does.
HTH, Brian
>
> Just collected an e*ay Tamron 500/8 SP mirror lens from the post office --
> seems fine so far, though until I get stuff printed I'm not sure, of course.
>
> Question: it focuses fine all the way up to infinity -- but then it'll
> focus a bit further. The focus scale on the lens makes it pretty clear that
> this
> is deliberate -- there's a mark at infinity, and then the scale continues a
> bit
> -- but why? What's the advantage of focussing further away than infinity?
>
> thanks,
>
> -- dan
< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
|