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Thread: Radioactiviy in lenses

  1. #1 Radioactiviy in lenses 
    New Member
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    Dec 2013
    Hello everybody

    I want to consult something with you all. Let's see, recently I bought this SMC Pentax 50 1.4, which seems to be radiactive. Until 80s Torio was used because this element allow to create low dispersion lenses.

    In many photography forums, there're jokes about these lenses, like "I have it and giant spiders run around my house". But i would like to know how much importance does it have actually. I mean, I don't think you're gonna loose your hair because you have it, but I keep questioning what the hell is happening there, is it dangerous, is it not?

    I don't know to much about radioactivity, and since then I want to know more. Hope here's someone who can help me with all this!

    Thank you all!

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  3. #2  
    Brassica oleracea Strange's Avatar
    Join Date
    Oct 2011
    I hadn't heard of this before. Unless you are carrying the lens around all day, I wouldn't worry too much.

    This article has some info on the equivalent does: A Look at the Radioactivity of Old Manual Lenses

    A list of possibly affected lenses here: Radioactive lenses - Camerapedia

    If you are using film, then I would be more worried about any potential fogging effects - so don't keep the lens on the camera all the time.

    ei incumbit probatio qui dicit, non qui negat
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  4. #3  
    Bullshit Intolerant PhDemon's Avatar
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    Feb 2013
    Newcastle-upon-Tyne, UK
    What is the radioactive material in the lens? Is it Thorium? (the closest I can come up with for Torio as an element) and if so which isotope? This link may be useful Isotopes of thorium - Wikipedia, the free encyclopedia as it lists the isotopes of thorium and the half lives etc. If the isotope you have decays via alpha emission you haven't got much to worry about unless you eat it or inhale it, beta and gamma radiation would be a little more concerning...

    This link seems to be saying that the main worry is if the Thorium is in an eye-piece where it would have close contact with the eye for prolonged periods but also talks about the beta and gamma emission and gives dose estimates.
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  5. #4  
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    Dec 2013
    Yes Thorium, and as I have read it's Thorium 232. It's funny I've already read all those links... maybe I'm spending to much time with this matter xD

    I don't know... the non-radioactive version is three times more expensive... xD Hard to decide
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