Archived posting to the Leica Users Group, 1996/07/20

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To: leica-users@mejac.palo-alto.ca.us, leica-users@mejac.palo-alto.ca.us
Subject: Re: 90 mm Leica lenses.
From: "Roger L. Beamon" <beamon@primenet.com>
Date: Sat, 20 Jul 1996 12:58:26 -0700 (MST)
 
>The physical base line is for all M-models the same 69.25 mm. This figure 
>has to be multiplied with the magnification off the rangefinder.
>For the M3 0.9, for the M6 0.72. This muliplication gives the effective 
>baseline which  determines the theoretical accuracy off the rangefinder. 
>That's why the srcew leicas from model 3 have a magnification of 1.5 wich 
>gives with a physical baseline of 38 mm an effective baseline of 57mm. 
>So in theory the screw leicas are mor accurate than the M6 which has 
>an effective baseline of 49.9mm.
>Off course also the mechanical accuracy of the mechanism is important and 
>also improved over the years.
>
>The CL has an effective baseline of 31.5 and is therefore not accurate 
>with long and/or fast lenses at open apertures.I often use a slim 
>tele-elmarit 90 on my CL but it definitely does not focus well at 2.8.
>
>
>Greetings,
>
>		Michiel.

Thanks, Michiel. I left the critical word out of my post, ie. "effective".
Indeed, the effective length is what counts!
     --
     Roger Beamon,  Naturalist & Photographer
                               Docent:  Arizona-Sonora Desert Museum
                               Leica Historical Society Of America
                               INTERNET:  beamon@primenet.com