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RE: [OM] Stop Down Metering

Subject: RE: [OM] Stop Down Metering
From: "Piers Hemy" <piers@xxxxxxxx>
Date: Thu, 28 Aug 2003 22:34:04 +0100
The three lenses you mention are the exceptions Iwert.  Think of the 8mm - a
very large part of the film frame is not taken up by image, but by darkness,
because it's a fisheye lens.  So the meter is fooled into thinking that
there is much less light in the 'image' than is actually in the true image.
And thus it indicates a much longer exposure time than you know is really
necessary.

As best I know, both the shift lenses are manual diaphragm, for which the
'hard-wired' aperture lever is set to the f/2 position (yes, I know they are
not f/2 lenses, but that is the way it is), which does indeed provide the
metering system with the baseline.  Just as on the manual extension tubes,
where you could be fitting a f/1.2 lens - the aperture lever is still at
f/2.

Hope that is clear

Piers


-----Original Message-----
From: owner-olympus@xxxxxxxxxxxxxxx [mailto:owner-olympus@xxxxxxxxxxxxxxx]
On Behalf Of iwert
Sent: 28 August 2003 20:16
To: olympus@xxxxxxxxxxxxxxx
Subject: Re: [OM] Stop Down Metering


Well,

How comes then that with the 8mm f2.8 zuiko fisheye, the OM3's meter is way
off, even stopped down. This in a range of like 1/60 actual exposure and
about 1/4 sec indicated? I think the laver communicating the aperture to the
body has some use, otherwise the meter does not know where to start from...
(like a division through zero). On the manual 35 shift and 24 shift, there
is a lever indicating the max. aperture to the body, i.e. f2.8 or f3.5. If
this lever is not there, there is no acurate metering possible?

Or where am I wrong?

Iwert
>
>> The meter knows what's going on with the lens in a manual lens 'cause
>> the lens actually stops down when you turn the ring... Aperture gets
>> smaller, less light, meter reacts accordingly.  Automatic lens fools
>> the meter via the lever you're referring to into thinking there's
>> less light there as you turn the aperture ring.
>
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