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Re: [OM] Stop Down Metering

Subject: Re: [OM] Stop Down Metering
From: Jim Brokaw <jbrokaw@xxxxxxxxxxx>
Date: Thu, 28 Aug 2003 17:11:52 -0700
on 8/28/03 12:41 PM, fred42@xxxxxxxxx at fred42@xxxxxxxxx wrote:

> Hi there Jeff,
> 
> Thanks for your help.
> 
> Would I be correct in saying that in practical terms I stop the lens down to
> the aperture I need and then set the shutter speed to get the meter as normal
> to between the +/- and then shoot?

Yes, this is the correct technique. When the meter needle is centered
between the + and - marks, the exposure is correct. This is the case whether
the lens is a stop-down lens stopped down, or a Zuiko with the aperture
fully opened.
> 
> If that is the case it makes me wonder what is happening mechanically with an
> auto-diaphragm lens. I understand the lens communicates its setting back to
> the body via a lever but if that lever is not in use with the manual diaphragm
> lens how does the meter know what is going on?

There are two levers on the back of the Zuiko (or other full-aperture
metering lens). One stops the lens down, the other tells the meter what
aperture the lens is set to. You can see this on the back of the Zuiko; when
the aperture ring is turned one lever will move in sync with the aperture
ring. This is relaying information to the meter, telling it what the
aperture will be when the lens stops down for the exposure. The alternative,
if this lever is missing, is to stop the lens down already, so the meter
sees the actual exposure light amount in advance.
> 
> Or am I getting confused?
> 
> Dan.
> 

No confusion, grasshopper... enlightenment <g>
-- 

Jim Brokaw
OM-'s of all sorts, and no OM-oney...





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