I think Simon's point is that the camera body doesn't know the relationship
between the maximum aperture and the indexed aperture since the maximum is
variable and the indexed isn't.
The answer is to meter using the constant aperture dot, since this limits
the maximum aperture and sets the relationship to the next smaller aperture
as a constant. The lens will then actually behave as a constant max aperture
lens, ie the aperture closes down all on its own as you zoom out,
independently of the stop down lever. On the 35-70 there is a noticeable
dimming of the viewfinder as you move from max to constant aperture at the
35mm setting, but of course no further dimming as you stop down further
unless you push the DOF preview.
Metering at max aperture will caused the error Simon describes. Of course in
OTF auto, this is all academic.
Julian
----- Original Message -----
From: "Piers Hemy" <piers@xxxxxxxx>
To: <olympus@xxxxxxxxxx>
Sent: Sunday, January 16, 2005 10:32 AM
Subject: [OM] Re: Zuiko 35-105 question
>
> No, it doesn't need to know the f/stop. It needs to know:
> 1 How much light is cominh through the lens at fully open aperture;
> and
> 2 By how many f/stops the lens is stopped down below its fully open
> aperture.
>
> It therefore doesn't matter to the camera metering system whether the lens
> is a 500/8 or a 50/1.2 and thus the position of the aperture reporting
> lever
> is simply the lens' actual aperture setting relative to fully open
> aperture
> - it does not report that "this lens is currently set at f/11". Take a
> look
> at a 500/8, compare it with a 50/1.2 and you will see what I mean.
>
> --
> Piers
>
> -----Original Message-----
> From: olympus-owner@xxxxxxxxxx [mailto:olympus-owner@xxxxxxxxxx] On Behalf
> Of Simon Worby
> Sent: 16 January 2005 08:43
> To: olympus@xxxxxxxxxx
> Subject: [OM] Re: Zuiko 35-105 question
>
>
> ---snip
> Since the camera needs to know what f-stop is selected to give correct and
> accurate light meter readings, how does it know (or doesn't it?) on the
> earlier model when the aperture lever should in fact be somewhere between
> 3.5 and 4.5 (i.e. at anywhere longer than 35mm), but isn't? Or are the
> light
> meter readings just up to about 1/2 stop out?
>
> --snip
>
>
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