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  1. #1
    Mustafa Umut Sarac's Avatar
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    Strontium in Leitz and Kodak Fluro Lenses, Radiation Sources

    I spent couple of years slowly reading in military databases, patents and books. I found and posted an article before about Kodak and Leitz lenses night performances. When the color temperature changes , these lenses turns to strong reddish yellow colors on skins. I could not understand the reason for years and I found that the main reason was the use of partial dispersion glasses. The color scale changes to one color dominance with partial dispersion glasses. I think these glasses are neutral at daylight.

    I started to search in Leitz and Kodak patents and found that the use of % 20 strontium use in partial dispersion glasses. I need to indicate that half of the new Leica lenses are partial dispersion glasses.

    Strontium is used mainly in cathode tubes with barium and they dont emit x ray.
    That material is radioactive and strongest byproduct of nuclear explosions.

    Second radioactive source is Thorium Fluoride use in Leica glass coatings until 1990s.

    Third radiation source is thorium addition to glasses.

    I want to say may be thorium is not used by Leica now but strontium dominate the patents and all world optical glass is coming from Kodak and Leitz Research labs.

    Mustafa Umut Sarac
    Istanbul
    Last edited by Mustafa Umut Sarac; 11-30-2013 at 01:24 PM. Click to view previous post history.

  2. #2
    Maris's Avatar
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    Natural Strontium is not radioactive.
    The synthetic element Strontium 90 is produced in a number of nuclear processes but does not occur naturally. Strontium 90 has a half life of about 29 years and undergoes low energy beta decay. The radioactivity is so mild that your skin would protect you if you held a lump of it.
    What makes 90Sr probably the most dangerous component of nuclear fallout is that the human body can't distinguish it from Calcium. It gets built into the bones where its radioactivity smashes biological processes at point blank range.
    Tragically, children forming and laying down bone are most at risk. Treatment is difficult because whatever pulls 90Sr out of the body depletes Calcium as well.
    Photography, the word itself, invented and defined by its author Sir John.F.W.Herschel, 14 March 1839 at the Royal Society, Somerset House, London. Quote "...Photography or the application of the Chemical rays of light to the purpose of pictorial representation,..". unquote.

  3. #3
    Mustafa Umut Sarac's Avatar
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    Maris,

    Thank you shedding more light. Do glass makers use natural or manmade strontium ?

    Thank you,
    Umut

  4. #4
    Mustafa Umut Sarac's Avatar
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    Our friend Maris sent me a pm and I find it I must put it here.

    The radioactive Strontium 90 did not exist freely on earth before the atomic and thermonuclear atmospheric bomb tests in the 1950s and 1960s. It cannot be used in the making of glass because it undergoes beta decay into Yttrium 90 and this spontaneous conversion has a half life of only 28.8 years. The Yttrium 90 changes to Zirconium 90 and this reaction has a half life of only 64 hours. Any glass made of radioactive Strontium would crumble into Zirconium sand in only a few decades.

  5. #5
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    Thorium was commonly used in Lens glass. Most often found in the Pentax f1.4 screw mount lenses. Turns the Glass Yellow with time, but a day or two in strong sunlight seems to bleach it back. (don't accidentally focus the light and start a fire).

    yes, Thorium IS radioactive.

    For more details try to find a copy of Living With Radiation: The First Hundred Years
    By William Kolb and Paul Frame { http://periodictable.com/Files/LivingWithRadiation.html }
    Charles MacDonald
    aa508@ncf.ca
    I still live just beyond the fringe in Stittsville



 

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