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Re: [OM] Speed of lenses

Subject: Re: [OM] Speed of lenses
From: "John A. Lind" <jlind@xxxxxxxxxxx>
Date: Sat, 07 Oct 2000 23:58:04 +0000
At 23:55 10/7/00 , Dirk Wright pondered:
>
>So, if you buy one of those nifty Mamyia M645-to-OM adaptors and slap on a
>Sekkor 80mm f/2.8, what do you get? It's still 80mm, but what is the maximum
>aperture? f/2? f/1.2? What about that Sekkor 80mm f/1.9, the fastest medium
>format lens ever made? What do you get? I can't do the math, to much
>wine..........<hick>
>
>Be seeing you.
>
>Dirk Wright

I'd *love* to see the mechanical part of an adapter that allows an M645
lens to link to the meter biasing lever.  It's external on the M645 similar
to the old Nikkor AI lenses!   ;-)

Hmmmmmm.  If my synapses fired correctly, the "thought experiment" results
are an 80mm lens at f/2.8 with the diagonal AOV for an 80mm for 35mm
format, approx. 30 deg.   All the extra light is in the large outer part of
the image circle that wouldn't get used (at least 75mm dia. with a 50 deg.
AOV)!  The adapter would have to mount the lens the same distance from the
film gate as the M645 does for it to focus properly, and it would therefore
have the same image circle on the OM film gate as on the M645 film gate.
What would be really nifty is an adapter that allowed shifting it to make
use of the large image circle!

Same applies to the 80/1.9, except you'd have an 80/1.9, which BTW I've
been *very* tempted to buy!  Supposedly it's slightly softer than the f/2.8
although I haven't researched it that thoroughly.

-- John

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