Radioactive lenses - yikes!

Discussion in '35mm Cameras and Accessories' started by ErosP, Oct 15, 2012.

  1. ErosP

    ErosP Member

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    Hello again my APUG friends...

    Dropping in to share a link that might be of interest to the community; came across a blog posting via www.petapixel.com about the radioactivity found in a number of the older lenses still floating about. Hopefully I don't scare anyone with this stuff but it's an interesting view nonetheless:

    http://bit.ly/T5401h

    It would be interesting to compile a database of these lenses... what do you think?

    All the best,
    Eros
     
  2. BrianShaw

    BrianShaw Member

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  3. Bill Burk

    Bill Burk Subscriber

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    OK but usually I have a camera body between rear element and my body.

    On the other hand, this is a good caution not to use the lens as a loupe.
     
  4. E. von Hoegh

    E. von Hoegh Member

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    http://www.apug.org/forums/forum52/111108-wear-your-lead-vest-when-using-these-lenses.html
     
  5. 2bits

    2bits Member

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    I remember reading about all the radioactive lenses some 30yrs ago. The amounts are very small . We are subjected to much worse on a daily basis anymore.
     
  6. LarryP

    LarryP Member

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  7. Pumalite

    Pumalite Subscriber

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    They might have a little Thorium, but boy; are they good. I'm referring to the Super-Multi-Coated Takumars.
     
  8. Jeff Searust

    Jeff Searust Member

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    these lenses are less than a bunch of bananas...

    I work in a building made of granite--- I can't even measure the radioactivity in a thorium lens because of the very high background coming from the building itself.
     
  9. Aron

    Aron Subscriber

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    Thank you. The people who built the original sarcophagus over the exploded Chernobyl power plant were in real danger, not the photographers who like to think more about the small amount of radioactivity of their lenses instead of what to put in front of them.
     
  10. E. von Hoegh

    E. von Hoegh Member

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    And in the kitchen...http://www.medicinenet.com/artificial_sweeteners/page8.htm
     
  11. Worker 11811

    Worker 11811 Member

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    Thorium only emits alpha particles. Right?

    I imagine that if you account for the amount of time the average person spends in proximity to a thorium coated lens, one would be in more danger from getting a sunburn.
     
  12. benjiboy

    benjiboy Subscriber

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    The lenses weren't coated with Thorium,Thorium Dioxide was part of the glass recipe to make it low dispersion.
     
  13. Gerald C Koch

    Gerald C Koch Member

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    Yes and no. The most abundant isotope 232Th decays mainly by alpha emmision but also by spontaneous fission and very rarely emission of two beta particles. The daughter isotopes must also be considered. The principal isotope of thorium decays as follows;

    232Th -> 228Ra -> 228Ac -> ...

    Both of the first two daughters decay by beta emission. There may be a gamma emitter in the chain. If you are interested you may trace the decay chain which ultimately results in a stable lead isotope.
     
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  15. Yashinoff

    Yashinoff Member

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    Isn't anybody worried about the fact that lenses are made of glass? And glass can shatter? Scary stuff to be holding up near your eyes! Yikes!
     
  16. mopar_guy

    mopar_guy Subscriber

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  17. PentaxBronica

    PentaxBronica Member

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    I watched a documentary recently which interviewed one of the official photographers who covered the cleanup. He went out on the roof with one of the teams shovelling debris back into the reactor building (they wore lead-lined protective clothing and were only allowed out for a few seconds - it was pretty much a case of one shovel load over the edge, then run for it). When he came to develop his film he noticed that it had marks at the bottom of the frame, caused by the radioactive wreckage he'd been walking amidst.

    Given that these lenses don't appear to fog film I wouldn't worry unduly. The natural background radiation in some areas will be higher.
     
  18. tomfoo13ry

    tomfoo13ry Member

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    Which is why I'm currently developing a lens that uses Jell-O instead of glass...radioactive Jell-O but Jell-O nonetheless.
     
  19. LarryP

    LarryP Member

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    great Tom. just remember to make some in lemon orange and strawberry so we have built in contrast filters.
     
  20. Worker 11811

    Worker 11811 Member

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    I thought the lenses were coated with some thorium compound to improve their optical qualities but it makes more sense the way you say it.
    Thorium is IN the glass, not ON the glass... Got it!

    This is good to know. :smile:
    The reason I understood things to be the way I said is because xenon lamps and carbon rods are often doped with thorium and/or other rare earth elements to improve their spectral emission characteristics.
    The electrodes inside a high pressure xenon lamp are made from sintered tungsten that has a small percentage of thorium mixed in or coated on. I forget which.
    Regardless, I was led to believe that as long as you don't eat them or carry them around in your pocket, moderate amounts of thorium-treated (thoriated?) materials are mostly harmless and that you stand more chance of contracting cancer from a sunburn than you do from (conscientiously handled) thorium.

    Anyhow, it's good to know more about thorium and, now, I have something new to go read about. :smile:
     
  21. Newt_on_Swings

    Newt_on_Swings Member

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    I understand the decay of the radioactive elements in the lenses eventually turns them yellow. What I dont get is how putting the lens in bright sunlight or a UV lamp for a few days, eventually clears it up. Does anyone have an answer to that?
     
  22. Gerald C Koch

    Gerald C Koch Member

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    The radioactivity causes defects in the crystal lattice of the glass. These defects can be an atom out of place which absorbs light of a particular wavelength. The energy of the UV photons can knock the misplaced atoms back into place. Heat will also work but obviously cannot be used for lenses.

    Curiously UV light can also cause coloring of glass. Old whiskey bottles found in the American desert are often amber or purple from the exposure they receive and command a higher price on the antique market.
     
    Last edited by a moderator: Oct 16, 2012
  23. Newt_on_Swings

    Newt_on_Swings Member

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    Ah, thanks. That is really interesting, I always thought unstable elements always broke down into more stable forms over time, but I guess with enough bombardment you can knock them back. Kinda like what happens in a collider i guess.
     
  24. Gerald C Koch

    Gerald C Koch Member

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    Perhaps my post wasn't as clear as it should have been. It is true that radioactive isotopes eventually decay to stable ones. The UV photons cannot effect this decay in anyway. Once an atom decays you cannot reverse the process.

    Think of the atoms in the crystal lattice of the glass as marbles in the holes of a Chinese checkers board. Radiation has caused one of the atoms (marbles) to be knocked out of its hole. A UV photon can push the atom (marble) back into its hole.

    Even in a throium glass the majority of atoms in the glass lattice are either silicon or oxygen atoms. For simplicity I say atoms but in actuality they are present as ions in the lattice.
     
    Last edited by a moderator: Oct 16, 2012
  25. Newt_on_Swings

    Newt_on_Swings Member

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    Oh that makes it much clearer with that example. Science, always something new to learn!
     
  26. Soeren

    Soeren Member

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    Sh** radioactive lenses. Oh my, will they fog my film? :D
    Best regards