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Re: [OM] 500mm relfex lens question

Subject: Re: [OM] 500mm relfex lens question
From: Sean Chan <Sean.Chan@xxxxxxxx>
Date: Sun, 18 Jun 2000 13:08:45 +0900
William,

> > Another beginner question.  What is this reflex mirror lens? And what
> > is the term Catatrioptic mean?  I know I've misspelled a lot here but
> > the wife wants to take her nightly walk and ice cream stop so I gotta
> > be fast...
> 
> Reflex - as in SLR (Single Lens Reflex)...the mirror moves up and down.
>          What you're looking through the viewfinder is what the film
>          sees - there's no parallax error, etc.
> 
> Catadioptric - the use of refractive lens elements together with
>                concave/parabolic mirrors to "fold" a lens of a
>                designated focal length to a managable physical
>                length. Very popular with Meade and Celestron
>                (telescope) manufacturers.

I'm a complete idiot. It would help more if I read your subject and
question more carefully. A reflex mirror lens is a lens that's
folded down to a smaller size with the use of mirrors and lenses
(like catadioptrics). Effectively, it makes a 500mm or 800mm lens
to a smaller handholdable size. The disadvantage is that you don't
have an aperture to play with - it's usually fixed at F8, etc. Also,
out of focus highlights will have "doughnut" shaped rings. Maybe
this is a "feature" in some kinda photos but personally I find it
annoying.

Sean
-- 
Sean Chan         Sean.Chan@xxxxxxxx       http://www.msdw.co.jp
EI/UNIX IT Dept.  +81 3 5424-4318 (W)        +81 3 5424-4399 (F)
Morgan Stanley Dean Witter Japan Ltd., Yebisu Garden Place Tower
20-3, Ebisu 4-Chome, Shibuya-ku, Tokyo, JAPAN           150-6008

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