I am not sure about lead, or rather lead oxide but a frequent
clarifier or fining agent is arsenic. It seems to me that the use
of arsenic in glass making may have been banned or restricted.
Can't find anything via a web search. Some old optical glasses
were probably discontinued simply because there was not enough
demand.
On 3/9/2020 7:41 AM, Ed Sawyer wrote:
Carlos -
Is that the book that is on ebay:
https://www.ebay.com/itm/123656195916
or is there another book? Is it available online anywhere or could you scan/post yours?
re: unavailable distagon glass - it's likely that the glass they were talking about not being available was something with high lead content. There were multiple types of glass that were discontinued in the 1990s due to lead content in the glass. Sadly, there is no replacement for some of these. Canon had to reformulate a few lenses as a result (with lesser quality of MTF in the newer versions), such as the EF 85/1.2L. I would expect the distagon elements to fall into this category given when they were made and such.
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Subject: [rollei_list] Re: Thorium glass
Ferdi:
My little Carl Zeiss book about the lenses for the Rollei TLR
says among the lens features the Distagon 4/55 is a special lens
construction dedicated to the Rollei TLR camera design, however it does not
mention some rare glass in the lens composition.
Varlos
El dom., 8 mar. 2020 a las 16:29, Ferdi Stutterheim (<
dmarc-noreply@xxxxxxxxxxxxx>) escribió:
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