Archived posting to the Leica Users Group, 1997/07/29

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Subject: Re: Collapsible Summicron 50 (M3 D/S) -Reply
From: Dave Stedman <DSTEDM@corp.atl.com>
Date: Tue, 29 Jul 1997 13:42:11 -0700

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Be aware,

The "yellowish" tint in the coating can easily be mistaken for the
discoloration of radioactive glass.  Some, and I mean only a few
of the early 50mm Summicrons used a "rare earth" glass that
was truly radio active.  Not enough that would fog the film or harm
someone, but enough that after 40 + years, they are getting that
yellowish hue or patina.  BTW, If you want a warmer than normal
photo, these beauties will do it for you.

There has been some interesting articles on this subject with in
the last year or so in the LHSA journal.

Dave Stedman
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Date: Tue, 29 Jul 1997 12:02:52 -0700
From:  <leica-users@mejac.palo-alto.ca.us>
To: Leikon35@aol.com, leica-users@mejac.palo-alto.ca.us
Subject: Re: Collapsible Summicron 50 (M3 D/S)
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The softness was in the coating , not the glass.  Soft coating usually had a
yellowish
tint where-as the harder magnesium flouride was more magenta.
Re-polishing & re-coating early Summicron lenses comprise a large part of
John Van
Stelton's work.  He does an excellent job for about $100.


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