Archived posting to the Leica Users Group, 1997/08/01

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Subject: Re: 50 DR Continued
From: Stephen <cameras@jetlink.net>
Date: Fri, 01 Aug 1997 19:59:42 -0700
 
> > Don't the original rigid and DR Summicrons share the same optical
> formulae?
> >
> > Dan C.
>
> Dan,
>
> Yes they do.  I believe that all the DR Summicrons tested out at the
> exact focal length for which the Summicron was computed.

Optical formula and focal length are entirely two different factors.
Whether its a 7 element lens or a single element, they can have exactly
the same focal length. Number of elements can be the same, focal length
can be the same, and you can still have different optical formulas.

Stephen