Archived posting to the Leica Users Group, 1997/10/02

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Subject: Re: f/stops weird and wonderful
From: Marc James Small <>
Date: Thu, 02 Oct 1997 08:20:13 -0400

At 09:50 AM 10/2/97 +0200, Alf wrote:
> .. 2.2, 3.2, 4.5, 6.3, 9, 12.5, 18, 25 ..., with an additional mark at 
>f 2.9 for the Agfacolor filter in the early 30ies.

There are minor variations on the Stolz scale:  I have lenses which are
marked f/12, others f/12.5.  I believe the markings on the Summar are more
accurate than the list I posted.

The Agfacolor system was the first commercially available colour system.
It mandated the use of special filters both to take and to project the
slide.  The system was only sold for a couple of years before Kodachrome
and its ilk came on the market, though Leitz and several other
manufacturers built a fair number of lenses to accomodate it.

Marc  FAX:  +540/343-7315
Cha robh bas fir gun ghras fir!