Archived posting to the Leica Users Group, 2014/02/11
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]What were the series of leitz/leica lenses that had lanthanum glass in them? Sent from my iPhone On 12 Feb, 2014, at 7:06 AM, Peter Dzwig <pdzwig at summaventures.com> wrote: > As far as I can find out older lenses that contained lanthanum in order to > achieve high refractive indices, contained Thorium Oxide which is mildly > radioactive.I do not know if these are the only type involved. > > For more details see here: > > http://en.wikipedia.org/wiki/Low_dispersion_glass > > and here > > http://camerapedia.wikia.com/wiki/Radioactive_lenses > > which gives a fairly extensive list and here > > http://www.orau.org/ptp/collection/consumer%20products/cameralens.htm > > Peter > > > > On 11/02/2014 21:22, Marty Deveney wrote: >> There are better, more stable ways to make high refractive index glass. I >> think lanthanum was largely discontinued in camera lenses for these >> practical reasons rather than anything to do with health. >> >> Marty >> >> >> On Tuesday, 11 February 2014, Howard Ritter <hlritter at bex.net> wrote: >> >>> Lanthanum is mildly radioactive, but not so much so that its use in >>> eyepieces for astronomical telescopes is prohibited. Several >>> manufacturers >>> advertise that their products contain lanthanum glass. >>> >>> --howard >>> >>> >>> On Feb 11, 2014, at 6:51 AM, Peter Dzwig <pdzwig at >>> summaventures.com<javascript:;>> >>> wrote: >>> >>>> Guys, >>>> >>>> Knowing your expertise.... >>>> >>>> What is the issue with Lanthanum in lenses. I thought its use had been >>>> discontinued long ago on health grounds, maybe in the 50s, although what >>> the >>>> details were I don't recall. Now someone else tells me otherwise. >>>> >>>> ...were there other compounds discontinued for similar reasons? >>>> >>>> Peter >>>> -- >>>> >>>> =========================================================== >>>> Dr Peter Dzwig >>>> >>>> >>>> _______________________________________________ >>>> Leica Users Group. >>>> See http://leica-users.org/mailman/listinfo/lug for more information >>> >>> >>> _______________________________________________ >>> Leica Users Group. >>> See http://leica-users.org/mailman/listinfo/lug for more information >>> >> >> _______________________________________________ >> Leica Users Group. >> See http://leica-users.org/mailman/listinfo/lug for more information >> > > -- > > =========================================================== > Dr Peter Dzwig > >