Archived posting to the Leica Users Group, 2001/11/15

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Subject: Re: [Leica] Responsiveness of M6 meter at f/1.4 to f/2
From: Nathan Wajsman <wajsman@webshuttle.ch>
Date: Thu, 15 Nov 2001 18:48:32 +0100
References: <B8192440.1699C%jbcollier@powersurfr.com>

John,

I had not noticed it in Osterloh's book before, but I now looked it up (p. 43,
German edition) and sure enough, he says that, in effect, the actual maximum
aperture of a Noctilux is not f1 but somewhere around f1.1-f1.2. I do not own
one of those beasts anymore, but when I did, I never noticed the effect, and I
cannot produce it with my Summilux. perhaps Ray should have his camera/lens
combo checked after all.

Nathan

John Collier wrote:

> It is normal. The inherent vignetting of any optical system wide open causes
> this effect. It is most noticeable with the Noctilux. See Osterloh's Leica M
> book for a well illustrated explanation.
>
> John Collier
>
> PS: Try your local library for the book. I might be persuaded to scan the
> relevant sections out of my copy if you cannot locate it.
>
> > From: Ray Moth <ray_moth@yahoo.com>
> >
> > I've just noticed a peculiarity in the behaviour of the light meter in
> > my M6 TTL, using a 50mm Summilux-M lens. If I adjust the aperture from
> > f/1.4 to f/2 or vice versa, the meter doesn't register any change,
> > whereas a change in shutter speed does register.
> >
> > For example, if the meter indicates that f/1.4 at 1/500 sec. will give
> > the correct exposure, then I would expect f/2 at 1/250 sec. would give
> > the same indication but it doesn't; it shows over-exposure, as if I'd
> > selected the slower shutter speed but left the lens aperture at f/1.4.
> > Conversely, if I started at f/2 and 1/250, a change to f/1.4 and 1/500
> > would indicate an under-exposure. The lens aperture selector seems to
> > function properly. Has anyone else experienced this problem?
> >
>
> --
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- --
Nathan Wajsman
Herrliberg (ZH), Switzerland

e-mail: wajsman@webshuttle.ch

Photo-A-Week: http://www.wajsman.com/indexpaw.htm
General photo site: http://www.wajsman.com/index.htm



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Replies: Reply from Mark Rabiner <mark@rabiner.cncoffice.com> (Re: [Leica] Responsiveness of M6 meter at f/1.4 to f/2)
In reply to: Message from John Collier <jbcollier@powersurfr.com> (Re: [Leica] Responsiveness of M6 meter at f/1.4 to f/2)