Archived posting to the Leica Users Group, 1996/10/10

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Subject: Aperture Markings
From: Marc James Small <>
Date: Thu, 10 Oct 1996 10:57:30 -0400

Leitz originally marked the aperture on its lenses in the 'Continental' or
Stolze sequence (f/1.1, 1.6, 2.2, 3.3, 4.5, 6.3, 9, 12.5, 18, 25, 36).
After World War II, they phased this out and replaced the Stolze sequence
with the 'Universal' or 'International' scale we know today (1, 1.4, 2, 2.8,
4, 5.6, 8, 11, 16, 22, 32).  I would suspect all M lenses use the
International scale, though vestiges of the earlier usage persist in the
maximum aperture of the 3.5/35, 3.5/50, and 4.5/135 lenses).  

The Stolze-scale lenses opened to f/36 for the 9cm Elmar and 13.5cm Hektor
lenses, and this was changed to f/32 when production shifted to the
Universal scale.  On the other hand, normal lenses were limited by
diffraction effects, especially in pre-coating days, to a larger minimum
aperture:  the 1.5/50 Xenon only going to f/9 and all of the 3.5/50 lenses
only stopping to f/18 until the International Scale was adopted.

Both of my collapsible 90mm Elmars open to f/32 as does the rigid lenshead I
use on my Bellows.

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