Archived posting to the Leica Users Group, 1998/08/18

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Subject: [Leica] various topics
From: Erwin Puts <>
Date: Tue, 18 Aug 1998 20:19:27 +0200

You wrote:
>The way this lens was explained to me, Leica is using the Sigma optical
>formula, but with their specified glass.  Construction is by Kyocera and is
>very high quality.

This explanation is fully off the mark. An optical formala incorporates in
a completely integrated way the types of glass to be used. As any glass
type has inherent optical properties as for instance refractive index, and
as this RI is part of the optical equation you can not simply use a certain
formala and substitute glasses. It also gives a false impression of the
lensmaker's craft and creativity, especially the competences of the Solms
"optisches Rerechenb=FCro"  (Optical Design Department).