On Tuesday, June 11, 2002 at 14:19, Winsor Crosby
<olympus@xxxxxxxxxxxxxxx>
wrote re "Re: [OM] long telephoto advice" saying:
> >In <3D0612F3.15432.3F3583C@localhost>, on 06/11/02 at 03:10 PM,
> > Tom@xxxxxxxxxxxxx said:
> >
> >>I think that would be better. Mirror lenses lose almost a stop of
> >>light
> >> from the central 2nd mirror, so that f/8 becomes an f/11, slower
> >> than
> >>a 300/9.
> >
> >Are you sure that this is true of the Zuiko?
> >
> >---------------------------------------------
> >les clark / edgewater, nj / usa
> >---------------------------------------------
>
> I think that might be an exaggeration. To drop the light by 1 stop
> you would have to obstruct half the area of the lens opening. That
> would require a secondary mirror of about 52mm which is much larger
> than the one on the Zuiko which appears to be about 35mm.
>
> In addition the Zuiko rather stands out from the usual mirror lens
> with an evenly lit field, good correction, and good contrast. --
> Winsor Crosby Long Beach, California
Cross off the "evenly lit" part and you'd be right.
Tom
------- Quidquid latine dictum sit, altum viditur -----------------
,__@ Tom A. Trottier +1 613 860-6633 fax:231-6115
_-\_<, 758 Albert St.,Ottawa ON Canada K1R 7V8
(*)/'(*) ICQ:57647974 N45.412 W75.714
---------------------------------------------------------------------
Laws are the spider's webs which,
if anything small falls into them they ensnare it,
but large things break through and escape.
--Solon, statesman (c.638-c558 BCE)
< 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 >
|