Archived posting to the Leica Users Group, 2010/09/25

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Subject: [Leica] DR contrast and the 'rare earth' Summicron
From: sethrosner at nycap.rr.com (Seth Rosner)
Date: Sat, 25 Sep 2010 06:54:49 -0400

Phil & others,

 

I believe you are confusing two different things. Some of the early 50
Summicrons ( they were all collapsible) were manufactured with glass one of
whose metallic 'rare earth' elements was thorium. It was this rare earth
that resulted in the yellowish tint and the slight radioactivity emitted by
a number of the elements. Leitz recomputed, more accurately re-designed the
50 Summicron, i.e. the 1956 DR/Rigid Summicrons, with what they described as
thorium-free glass. These lenses had glass elements with the 'rare-earth',
lanthanum, described in the literature as LaK9 glass. A reason I
occasionally used to sign off on an LHSA communication: LaK9 = Love and
Kisses 9 times. ;-)

 

Seth  



Replies: Reply from chs2018 at med.cornell.edu (Chris Saganich) ([Leica] DR contrast and the 'rare earth' Summicron)
Reply from photo.forrest at earthlink.net (Phil) ([Leica] DR contrast and the 'rare earth' Summicron)