Re: [Leica] Radioactive lenses

[Dan Cardish <dcardish@microtec.net>]

In the 3/99 issue of Leica Fotographie, there is an interview with Norbret
Meinert, who worked on the Leitz Glass laboratory.  He claims that "Ernst
Leitz refused to consider using this type of glass [thorium]", but then
went on to state that "We first of all began experiments in spite of
misgivings, with that thorium glass, using some of it in a small series of
the Summitar.  The results were so encouraging..."

Dan C.

At 01:33 AM 02-08-99 EDT, you wrote:
>Ed,
>
>I call your attention to an article in the LHSA Viewfinder 29/3, third 
>quarter 1996.
>
>In an article on the early 50/2 Summicrons, Bill Gordon wrote a well 
>researched article about the use of thorium oxide glass in these lenses.  
>Bill reports low but measurable levels of radiation from these lenses as 
>tested by a Geiger counter.  He also cites an earlier report by Dr. Cyril 
>Blood in the Leica Historical Society Newsletter on the use of thorium oxide 
>by Leitz in the Summitar* and early Summicron lenses.  According to Bill, 
>Leitz never officially acknowledged the use of these radioactive elements.  
>This is understandable in that they would not want to alarm employees or 
>users of the radioactive elements in these lenses.  Many other manufacturers 
>of optical lenses also used this radioactive glass.
>
>If radioactive thorium oxide was not used in the early Summicrons, how do
you 
>explain the positive readings obtained with a Geiger counter?
>
>Bill Rosauer 
>
>