Archived posting to the Leica Users Group, 2001/07/27

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Subject: Re: [Leica] Radioactive glass in M lenses ?
From: "Daniel Post" <dpost@triad.rr.com>
Date: Fri, 27 Jul 2001 16:44:25 -0400
References: <061d01c1167a$58ec8000$604d149a@hughthompson> <3.0.6.32.20010727100804.00b19d20@pop.infi-net.mindspring.com>

Marc
I imagine that the Schott glasses are ideal for dispensing fine single
malts, neh? (hic!)

Dan (TGIF) Post
- ----- Original Message -----
From: "Marc James Small" <msmall@roanoke.infi.net>
To: <leica-users@mejac.palo-alto.ca.us>
Sent: Friday, July 27, 2001 10:08 AM
Subject: Re: [Leica] Radioactive glass in M lenses ?


> At 02:27 PM 7/27/01 +0200, Mxsmanic wrote:
> >Leica and most other manufacturers of good lenses use special glasses to
> obtain
> >the optical characteristics they require.  At one time, Leica had its own
> glass
> >lab, and at least one of the glasses it produced contained thorium oxide.
> >Thorium is a mildly radioactive metal similar to uranium in its
> radioactivity.
> >The use of thorium and lanthanum oxides made it possible to obtain very
high
> >indices of refraction with low dispersion, which is useful for correction
of
> >many aberrations.
>
> The affected lenses were pre-production and very early production 2/5cm
> collapsible Summicrons.  See Dr Blood's article in VIEWFINDER four or five
> years back.
>
> Leica did, and still does, to my knowledge, have a laboratory for optical
> glasses, but it has never made its own glass.  Until 1926, it used glass
> from CP Goerz in Berlin and then, after the Zeiss Ikon merger closed that
> facility, shifted to Schott glass, first from Jena and, after the Second
> World War, from Mainz.  In recent years, some of the Schott glasses
> supplied have come from Hoya, who manufactures them under license.
>
> Marc
>
> msmall@roanoke.infi.net  FAX:  +540/343-7315
> Cha robh bąs fir gun ghrąs fir!
>
>

In reply to: Message from "Hugh Thompson" <painfree@istar.ca> ([Leica] Radioactive glass in M lenses ?)
Message from Marc James Small <msmall@roanoke.infi.net> (Re: [Leica] Radioactive glass in M lenses ?)