Thorium in my lens? nope.

Discussion in '35mm Cameras and Accessories' started by One_DaveT, Nov 22, 2009.

  1. One_DaveT

    One_DaveT Member

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    Tonight I just learned about the use of thorium in lenses up until 1980's. This prompted me to go dig out my 60's vintage civilian defense geiger counter, which I bought years ago after some goof ball medical technician made a wise crack about the half life of the liter of barium I had just quaffed for a cat scan. (fwiw, the drinkable stuff is from a non-radioactive isotope).

    Anway, I put my old lenses to the test. I can say after scanning for alpha and beta particle that I believe the following lenses are Thorium-free:

    Nikkor-N 24/2.8 pre-AI
    Nikor-S.C 50/1.4 pre-AI
    Nikkor-P 105/2.5 pre-AI
    Nikkor-Q C 200/4 pre-AI

    FWIW, I checked a few other lenses:
    Zuiko OM 50/1.4
    Minolta Rokkor 200/3.5
    Minolta Rokkor 50/1.7

    After reading that Thorium in lenses goes back to 1937, I checked my Exakta lenses: Steinheil 135/3.5, Westenar 50/2.5..... nope.

    In hindsite, after reading wikipedia, it doesn't seem like much of an issue anyway. It says alpha particles from thorium can't even penetrate human skin, so even if I did have a thorium lens, it likely wouldn't be a concern unless I breathed the pulverized dust of a broken lens. Given that the use of it in commercial lenses stopped around 1980 makes me wonder if three-mile island incident in 1979, might have made marketing thorium lenses impossible, and lead to the end of it's use.

    Interesting diversion for the evening though.
     
  2. sangetsu

    sangetsu Member

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    I have 3 thorium lenses by different manufacturers, but I don't have any concerns about them affecting my health. I believe the main reasons thorium stopped being used were 1, improvements in technology allowed other materials to be used in it's place, and 2, concern over worker's safety. It's true that thorium lenses put out too little radiation to do any harm, but the large amounts used in the manufacturing of the glass likely posed a greater health risk.
     
  3. benjiboy

    benjiboy Subscriber

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    I have the Canon FD 35mm f2 Thorium lens, and it's such a great lens I'll take the risk, and wear lead lined boxer shorts.:D
     
  4. MikeSeb

    MikeSeb Member

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    If you smoke, drive a car, climb a ladder, or fire up a barbecue grill, focus on reducing those very real risks, rather than the risk of thorium-emitted alpha particles.

    If the OP was at all seriously concerned (hard to read people onlne), then this was yet another example of the common human fixation on remote, even minuscule, risks while ignoring the real ones whose abatement, however, would require habit change or other inconvenience.

    And this tendency would be merely an amusing quirk were it not for its implications for public policy. And yes, widespread irrational public fear, leveraged by the lunatic part of the enviro movement, HAS likely prevented more widespread adoption of nuclear power generation in the US.

    (Hadn't planned on mounting the soapbox quite so early this morning!). ;-)
     
  5. Marco B

    Marco B Member

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    Well, in terms of the uncontrolled disastrous human population growth, I would suggest going without :tongue:
     
  6. benjiboy

    benjiboy Subscriber

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    No fear, got to protect the family jewels.:wink:
     
  7. FilmOnly

    FilmOnly Member

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    I thank you for the test results. Any data in regard to radioactive lenses is always helpful. Though some have dismissed the detrimental effects of thorium in lenses, others have found problematic levels of radiation. Here is an interesting link: http://forum.mflenses.com/best-of-manual-50mm-f1-4-t11295.html

    With regard to the subject of overpopulation, the common contemporary hypothesis is gravely erroneous. The world is simply not becoming overpopulated. Europe is shinking at an alarming rate, and, if the current trend continues there, Europe will not repopulate itself (as the continent is currently well below its repopulation rate). The entire population of the earth could fit into the land area of the US, with plenty of room. Likewise, the entire population of the US could fit into the state of Texas, again with ample space. Here is an interesting discussion: http://economics.gmu.edu/wew/articles/99/Population-Control.htm
     
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  8. rthomas

    rthomas Member

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  9. budrichard

    budrichard Member

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    As a Nuclear Engineer I would not put too much confidence in your measurements unless you had a radioactive source to verify calibration/function of a GM device from the 1960's.
    In any event unless you grind up a lens containing a radioactive element and injest, there will be no harm from external exposure and since the glass will quickly pass through your digestive system, no quantifyable internal effects anyway.-Dick
     
  10. FilmOnly

    FilmOnly Member

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    I would be interested to know how the 50/1.4 S tests on correctly functioning equipment. The brownish tint of the lens gives me pause.
     
  11. Marco B

    Marco B Member

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    Well, as for the Netherlands, I can tell you the influx of immigrants, and the after effects of the baby-boom after WOII, combined with continuously increasing life expectancy, means we will still see a net growth of the number of people living here in the next one or two decades. Yes, the population ages, but that doesn't mean it's shrinking! And the pressure on land resources continuous. Even the elderly need homes...

    And to be honest, I don't consider a few million less people (and cars and endless stretches of tarmac and concrete) here in the Netherlands a bad thing! Bly me, I can't wait for it... Viva la natura!

    And after that: we'll just have to open up the flood gates. I have no doubts many people will want to join us here in Europe and the US...
     
  12. DWThomas

    DWThomas Subscriber

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    Yeah but, there is more to the problem than square feet per house, NYC sure as hell doesn't grow its own food or supply its own water or fuel. Here in the US we maintain a lavish, high energy consumption lifestyle by exploiting not only our own land mass, but that of many other countries, a source of some of our current problems.

    I concur that thorium lenses are unlikely to be of major import in the general scheme of things. Glass and ceramics from earlier periods used uranium compounds to get interesting yellows too.

    DaveT
     
  13. FilmOnly

    FilmOnly Member

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    In terms of fostering and maintaining a sensible--and organic--system of agriculture, encouraging the wise use of God-given resources, and the importance of advancing the common good, I could not agree more.

    Please review my post. My post simply states the facts in regard to the myth of overpopulation.
     
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  15. benjiboy

    benjiboy Subscriber

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    My eldest son is a physicist, and I asked him to look into the matter and he assured me there is no danger.
     
  16. Marco B

    Marco B Member

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    Yeh, sure, I think the basic problem is though, that we haven't stated in what context we review "over-population". Sure enough, if we simply count the number of square meters a pair of average sized shoes takes up, we could even fit all the upcoming 9 billion expected soles on the post stamp size of the Netherlands...

    Question is: is that a useful measure of over-population??? :wink:
     
  17. Marco B

    Marco B Member

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    In fact, I did a quick calculation: Since the Netherlands is about 33.883 km2 land surface, in 2050 or so when we hit 9 billion, you are all welcome to join me here in the Netherlands if I am still around... (and the country hasn't disappeared below sea level)

    The good news: You can take your king sized bed with you! We will all have a whopping 3.76 square meter (eh,... +/- 42 square feet that is?) to ourselves! :D

    Marco
     
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  18. benjiboy

    benjiboy Subscriber

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    Aren't we getting a little off the point ?, my remark about Lead lined boxer shorts was a Joke.
     
  19. One_DaveT

    One_DaveT Member

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    Regarding Budrichard's comment, Yes, I believe many civilian defense geiger counters have a check source, to validate the geiger counter is functioning, including my CDV-700. I did check the source prior for gamma and beta readings. Regarding my comment about it being from the 60's.... I don't know that this is in fact true, as I see a web site that sells and calibrates my same detector. Though it appears they haven't changed the design, construction or components inside since the ~60's. Regardless, I'm comfortable with the accuracy of the information provided on the particular lenses I listed.


    To others, if it wasn't clear, after a few minutes of research on the subject, I'm not concerned. I suspect there is some truth in what Sanguestu brought up regarding risk is with manufacturers. Interesting factoid gleened was that in addition to improved refractive properties lenses, another use that thorium is sought after a potentioal replacement for uranium nuclear reactors, due to reduced waste.

    I did find it fascinating how a discussion on radioactive lenses could quickly lead to over population. Ben must have a reputation ;-)
     
  20. Larry.Manuel

    Larry.Manuel Member

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    Coleman stove lantern mantles contain thorium, too. When the lamp is first lit, the silk burns off, and a thorium oxide skeleton remains, which becomes incandescent in the gas flame.
     
  21. Jeff Searust

    Jeff Searust Member

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    I have one, and never really saw any image tint. Nice Super Takumar lens though. Here's a good shot of one;

    http://vapour-trail.blogspot.com/2007/02/super-takumar-50-mm-f14.html

    Mine is connected to a POS Honeywell Pentax.
     
  22. benjiboy

    benjiboy Subscriber

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    "I did find it fascinating how a discussion on radioactive lenses could quickly lead to over population. Ben must have a reputation ;-"

    That's right Dave the question was about Thorium in lenses, not lead in my pencil :tongue:
     
  23. Jim Chinn

    Jim Chinn Member

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    I have read that Aero Ektar lenses produced by Kodak used glass with Thorium. These lenses are pretty fast (2.5) and I have thought about getting one for wet plate. The radioactivity gave me a little pause, but as others have pointed out the glass "browns" over time and I don't know how this would effect the speed of the lens or transmission of UV rays, both critical for wet plate.
     
  24. BetterSense

    BetterSense Member

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    They don't anymore, although I understand that you can still get cheap chinese mantles that incorporate the thorium. It seems like thorium lamp mantles belong to a growing group including things like incandescent lightbulbs, CRTs, pseudoephedrine, robutussin, and other things that work too well and must be villified or banned.
     
  25. Ralph Javins

    Ralph Javins Member

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    For the tint of your lens, others have noted this also. One of the recommended cures is to place the lens without caps on a window sill in a south facing window for a few days (a week?) where sunlight can shine through the lens, and the coloration seems to go away. This also aflicted a couple of my Minolta AUTO ROKKOR-PF 1:1.4 f=58mm lenses. Some Asahi-Pentax Takumar lenses also show this effect.
     
  26. mhcfires

    mhcfires Subscriber

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    Lead lined boxers would be a little heavy. My back hurts enuff already. :D