Archived posting to the Leica Users Group, 1999/08/05

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Subject: RE: [Leica] Re: actual focal length
From: Simon Pulman-Jones <spulmanjones@lbs.ac.uk>
Date: Thu, 5 Aug 1999 21:29:35 +0100

Thanks for shedding light on this Dominique. It's nice to know that my lenses are so scrupulously honest!

>Can anybody explain how the numbers engraved on the barrel beyond the
>infinity markings relate to actual focal length? I find 00 on my Noctilux,
>05 on my 200/4 Telyt, and 10 on my 90 Elmarit-M. Is this variation from the
>nominal focal length in hundredths of a millimetre? If so, there appears to
>be no plus or minus indication.
>

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05 tenths of mm = 0.5 mm.
For your Telyt 200 the exact focal length is : 200.5 mm.
For your Elmarit 90 : 91 mm.
On my Elmarit R-90 I read : 95 <:-o). So... the exact focal length is : 89.5 mm.

I guess it could be important to know these data.
I know that japanese manufacturers "cheat" on the focal length of the
lenses. For instance my C**** 28-105 is a 30-95 according to CI. Leica does
not cheat even with the "japanese" leica lenses.

Dominique Pellissier