Warning, radioactive lenses!

Discussion in 'Large Format' started by pete_andrews, Jun 29, 2001.

  1. I was recently reading some previous postings and web articles about certain lens glasses containing radioactive elements, and wondered if any of my collection might be 'hot'.<br>Initially, I was more curious than worried, but after doing some tests, I'm now definitely worried, and I think my findings deserve wider attention.<p>I have a sample of a 7" Kodak Aero-Ektar, which is a lens that has a big reputation for being potentially radioactive.<br>However, all the articles I've read state that the radioactivity is mainly in the form of alpha emmission, and shouldn't give much call for concern, since alpha particles are quite low energy, and easily stopped by any solid object. I'm told that alpha particles can only penetrate about 40 microns into human tissue.<br>Anyway, to cut to the chase: I just got our radiation protection officer to run a geiger counter and a dosimeter over the Aero-Ektar, and he found that the rear element was quite hot, giving about 200 counts/second. Worse yet, we discovered that it was mainly GAMMA emmission, since even an inch of perspex and a steel plate hardly affected the counts at all. The active element used in making the glass is Thorium, and a quick check of the table of its decay products confirmed that they're mostly gamma emmitters, after about 6 years of decay.<br>Dosimeter readings showed that within 1" of the rear lens surface, the dose was above the limit allowed for monitored radiation workers, and only fell to the publicly allowable safe limit at more than 6" from the lens.<br>I don't think I'll be using that lens as a paperweight, or handling it too much from now on. By all modern standards, that lens would be classed as downright hazardous, and not to be used without protective clothing!<br>I'll be testing the rest of my lenses as potential gamma sources as well in the near future.
     
  2. Since infinity is 7" and it is safe at 6" and you are not going to
    carry it around in your pocket, I would not worry about it. Pat
     
  3. So, if you put it on a camera, and lock the shutter open, will it fog
    the film?
     
  4. Pete, since the part of my brain which is nearest the gg doesn't work
    anyway, I suggest you don't use the lens anymore and send it to me.
    That'll be two pints I owe you. Dave.
     
  5. There was an article about this 4 or 5 years ago in Shutterbug, I
    believe. It reported that Apo-Lanthars, certain early Takumars, and
    many other lenses are somewhat radioactive. A simple test is to leave
    the lens on a sheet of photographic paper in a darkroom for several
    hours, then develop the paper. Dark spots from radiation exposure
    will be readily apparent.
     
  6. Is this only present in older lenses or in new ones as well?
     
  7. Is this only present in older lenses or in new ones as well?
     
  8. I don't know if manufacturers are trying not to use radioactive
    materials, but the rare earths like lanthanium, thorium, yttrium,
    etc. are quite useful in adjusting refractive indexes, limiting
    dispersion, and absorbing UV in glass--it may be difficult to find
    replacements for them. I did some searching and can add Konica,
    Zuiko, and Steinheil to the list of companies that used rare-earth
    lenses--as well as the f/2.8 lenses in the Stereo Realist. Probably
    all the major lens companies experimented with them at one time.
     
  9. Pete,

    <p>

    200 counts/second seems a bit high. You're sure it is not 200
    counts/minutes. For LF, the other two "hot" lenses I know are
    Voigtlander Apo-Lanthar and Rodenstock Weitwinkel Perigon (1958
    vintage, 130 mm/F12). Both contain Lanthanum. From personal
    experience, Apo-Lanthar and Perigon are wonderful lenses and will not
    expose films under normal usage. No worry. They are not hot
    enough. On second thought, I'd better send my hot lenses to NYU for
    a safety check-up. Thanks for the note. Regards,
     
  10. Gosh, I wasn't aware of that! Is that the reason my older Takumars for Pentax 67 are becoming encreasingly warm
    in color?
     
  11. Pete: this is disturbing information indeed, and I wasn't aware of it
    in the least - and I'd used a Pentax 67 system with older lenses
    until recently. Am I safe in assuming that newer lenses are OK?
     
  12. There is no form of "safe" radiation, any radiation is potentially
    harmful, having said that, most watches give radiation off, your
    television radiates too! To say nothing of magnetic fields generated
    by high power electric lines!
    No there is no reason to worry about using a lens which uses
    radioactive elements.
    The yellow coloration of some Pentax and other brand comes from old
    adhesive which binds the elements and getting old changes color, can be
    fixed.

    <p>

    Dont't worry, be happy!
     
  13. I was a little hasty in minimizing the issue but I believe that any
    "old" lens would have been reduced the radiation by now we talk about
    lenses which are 50 to 30 years old and I believe that modern
    technology and norms are so stringent that nothing as bad as that could
    be produced just in the name of low -dispertion!
    However, thanks for raising the issue!
     
  14. Hi Andrea! Thanks for the tip on Pentax lenses getting yellow because of lens cement. You say it can be fixed? Can
    you give me some information and tell me if the price of such repair is not prohibitive?
     
  15. Radiation safety isn't something anyone should be offhand
    about, but all the information I have (thus far) says that the risks
    to human health from radioactive lenses are very small. The
    only occupational health hazard I could find was for the workers
    making the lenses and reports of eye damage from people
    spending long periods of time peering into rare-earth eyepieces
    on telescopes and microscopes.

    <p>

    Obviously Pete knows this, but it's worth pointing out that most
    western countries take radiation safety very, very seriously. If you
    live in Europe or the USA your local university, large hospital or
    town will have a radiological protection officer. If you are worried
    about a lens in your posession contact them - they will usually
    come and check things out at no charge, and even handle
    disposal in many cases.

    <p>

    I recently had to do this (I discovered a Cs calibration source
    when clearing my father-in-law's house) and asked the officer
    about the various famous 'hot' lenses. He was of the opinion
    that the risk was very low (provided you don't sleep with them
    under your pillow), and that if you did want to get rid of them,
    landfill was both legal (in the U.K.) and the safest option. The
    radioactive elements are safely encapsulated in the glass and
    won't migrate to groundwater, or form airborne dust, at a rate
    worth worrying about.

    <p>

    The Aero-Ektars are a little different from the most other famous
    radioactive lenses in that they are military items, first designed
    and produced in wartime. They were designed to be used
    'properly' and not by Joe Bloggs civilians who would sellotape
    them to the cat for a year and then look around for someone to
    sue when the cat died of distemper. It is therefore possible that
    these lenses in particular could be hotter than normal, quite
    apart from the fact that standards have changed quite a bit since
    the 1940s.

    <p>

    There is a lot of conflicting information about exactly what was
    the radioactive element(s) in these lenses floating round the
    internet, but Thorium and it's decay products are certainly part of
    the mix. Unfortunately my 7" Aero-Ektar was in Sweden when I
    was chatting with a fully-equipped radiological bod in East
    Anglia, so it's still an unknown, waiting in the cellar for my local
    expert to get back from sniffing round the sunken submarine
    reactors on the bottom of the White Sea. When he does so, we
    plan to do some gamma spectroscopy to find out just what is
    inside the lens. I'll report back once I have some data.

    <p>

    Incidentally, the fact that the rear elements of these lenses is
    usually yellowed all the way through is a pretty good indication
    that gamma emitters are involved. The change of colour will
    have also changed the refractive index and dispersion of the
    affected elements, so it might not work as well as it did when
    new anyway. In any case, unlike other aero lenses, the
    Aero-Ektars were designed for maxmimum brightness, not
    ultimate sharpness, so they're best kept for applications where a
    large aperture is required. They are the ultimate bug burner :)
     
  16. I'll try to answer as many points as I can.<p>Pat. Such gung-ho
    attitudes to radiation are all too common among radiation workers, but
    they go quiet when one of their colleagues contracts Leukemia or some
    other lymphatic cancer.<p>Geoffrey, I'll check again, but I'm sure
    it was 200 counts/second.<p>The previous postings I've seen on this
    lens all assert that the radiation is in the form of Alpha particles,
    and if that had been the case, then I wouldn't have worried, since a
    piece of ground glass, and the body of the lens itself would have
    stopped it.
    What we found was that the radiation was definitely mainly Gamma
    emission, and this is much more energetic. It passes almost unimpeded
    through most things, including the human body. Deep penetrating
    radiation like this is much more hazardous to health.<p>The Aero Ektar
    used Thorium, not Lanthanum in the glass, and this is the reason why
    this particular lens is such a 'hot' property.<br>I'll investigate
    lenses containing Lanthanum, if
    I can get hold of any, but I don't think they'll be as bad.<p>As
    someone else pointed out. There's no such thing as a safe dose of
    radiation. The probability of radiation causing a malignant mutation
    of a cell in the body reduces with the dosage, but the chance is still
    there, even with a declared 'safe' level.<p>My radiation savvy
    friend's reaction was "I wouldn't sit on that lens for any length of
    time, if I were you". Meaning that it was 'active enough to cause
    sterility if placed close enough to those 'sensitive' areas of the
    body for long enough. Now, while that scenario is pretty remote, it's
    not impossible that I would quite happily have handled and used that
    lens taking absolutely no care whatsoever, if I wasn't aware of the
    danger.<br>It's not the radiation hazard itself, it's the fact that it
    can be there without your knowledge that's the real danger. Once you
    know about the problem, then you can take the appropriate
    precautions. (For example: I used to keep this lens on top of the
    fridge that I store my film in, and I now know that this wasn't a good
    idea!)<p>I don't think that any modern lens would ever be allowed out
    of the factory if it was as potentially hazardous as this particular
    old Aero Ektar, but who can say for sure?<p>I don't think there's
    any definite link between the yellowing of an optical glass and it's
    radioactivity. The two aren't necessarily tied together, but it's
    probably worth checking out.<p>Finally, I'm not trying to be
    scaremongering over this. I'm just trying to convey my own surprise
    and concern at what I found in one particular sample of an old lens.
    It also seems to me that some of the previously published articles
    playing down this problem might have been a little too frivolous.
     
  17. Yellowing or browning of glass is a classic symptom of radiation
    damage, although in some cases a glass can be bleached if it
    was coloured to start with. Unscrupulous diamond dealers use
    X-rays to turn diamonds pretty colours for unwary 'fancy'
    collectors.

    <p>

    I have heard tales (good reference I know) of glovebox windows
    turned dark brown by radiation over the years. Usually this takes
    place at "a lab in Siberia", but Windscale is another popular
    destination.

    <p>

    Joking aside, it makes sense to find out as much as you can
    about the risk. It is also worth relating the risk to things like a
    daytrip to Aberdeen or using a Bluet camping light (thorium in the
    mantle). There are some jobs where you need that f2.5
    aperture.

    <p>

    Incidentally, when my father in law was clearing *his* father's
    house, he turned up a phial of radium (Run away! run away!). It
    turned out that his father had chosen to repeat the Curies'
    experiment and isolate Radium from pitchblende as his school
    project. Times have changes somewhat methinks.
     
  18. How scary! Your way of talking off-hand on the subject just adds to my anxiety. I have been sleeping for ten years
    with a bag full, among them two or three of these warm amber babies in my bedroom. Shall I consult an oncologist
    or go directly for the mute? Kidding set aside, are they any precautions worth taking?
     
  19. Just minimise the time spent with the lens close to your body. If
    you're not really close to the lens elements, gamma rays fall off
    in intensity with an inverse square law just like light, so the
    further away the lens is the less it can irradiate you. Don't keep it
    under your bed, or on top of your film safe. Pack it in your
    rucksack away from your body, not up against your spine. If you
    are sharing a tent or a bivvi bag with the, put them as far away
    from you body as you can.

    <p>

    If you want to be certain, find your local radiological protection
    officer and ask. He or She will be in the phone book.

    <p>

    With all risks it makes more sense to be aware of them than
    afraid of them. The consequences of falling into a crevasse are
    often fatal, but that means we take precautions like wearing
    crampons and roping up, not that we avoid glaciers altogether.
    It also makes sense to compare risks to other, similar risks we
    take without worrying in the slightest - hence my comment about
    radiation sources like granite houses and gaslamp mantles
    which we accept without question.

    <p>

    I actually believe that the various radioactive lenses are
    curiosities, not hazards. Pete's geiger reading does seem high,
    but note that even by today's safety standards, you are at the safe
    level for continuous exposure once you are six inches away.
    With a focal length of 7", you're fine even when focussing.

    <p>

    For what it's worth, I'm responsible for safety in a university
    research group that does a lot of X-ray spectroscopy, so I think I
    know what I'm talking about and can assess the risks for myself.
    I keep an Aero-Ektar in the house with my six-month old twins,
    but I don't store it under their bed - or mine.

    <p>

    However, I am reluctant to say 'forget it' , because there is so
    much confused and contradictory information about the
    Aero-Ektars floating about, and I want to do some real
    measurements before being certain. There are better and more
    convenient lenses which definitely have precisely zero risk of
    giving you cancer, so is even a small risk worth having that fast
    aperture around? The reason we take radiation seriously is that
    you have no sensation of being harmed until it is too late to do
    anything about it , which gives a certain incentive to educate
    yourself.
     
  20. Paul: If my Aero Ektar is typical, then as long as you don't bring the
    lenses in close contact with your body for any extended period of time
    (hours), then you really shouldn't worry.<br>Unfortunately, there's
    not much that will shield Gamma radiation completely. 2" of Lead or a
    foot or so of water will do the job, but distance is the cheapest way
    of protecting yourself.<p>Update!<br>I've just checked another old
    lens, a 14" f/9 Taylor-Hobson 'Cooke Apotal' process lens, which I
    suspect uses Lanthanum glass. This one drove the geiger counter to 300
    counts/second, but the emission seems to be mainly high energy Beta
    and X-rays this time. It was the rear element again that appeared to
    be the source.<br>This lens was 'safe' at a radius of only 2 or 3
    inches, and a 3mm sheet of Aluminium was enough to stop most of the
    particles.<p>A Kiev Mir-24N 35mm f/2 that I thought might be hot
    turned out to be completely clean.<br>I now have the use of a geiger
    counter for a day or two, and I'll be doing a sweep of my lens
    collection.
     
  21. Pete, Struan, thanks for this most informative discussion! Seems we will never look at some lenses the same as
    before. As you say, there is probably not much to worry if simple precautions are taken. But we live in an
    environment that exposes us to cummulate small risks, radio-activity being just one of them with the remnants of
    Tchernobyl, but then there is the electro-magnetism and other bad rays from the computer screen, the diluted
    poisons in food additives, the mercury in tooth cement, the space and UV rays from the damaged ozon layer, the
    pollution in the air and water, the pesticides in the veggies and fruits, and for some, the white and deadly volutes of
    tobacco smoke just to name a few...

    <p>

    I better stop here this depressing list. The man of the future will have to be a transgenic creature blended with some
    cockroaches genes in order to survive, or will simply not be :-(
     
  22. Heeee...heeee...eeeee...as someone who has had 9600 rads of
    radiation - I just wonder what you all think "safe" constitutes? The
    Dr.'s kept telling me it was good for me - although they all left the
    room prior to the linear accelerator being turned on. Sorry, Pete -
    just can't take this all that seriously - I just don't think most
    people have had enough radiation. Mutate or die...
     
  23. Steve, if you drop an Aero Ektar in your lap, the tingling won't be
    subtle :)
     
  24. 200 counts of gamma a minute! Almost makes me think twice about
    flying in commercial aircraft (at least above 35,000 feet).
    Wait! No problem! I'll just book flights that last less than two
    hours (One per year in normal latitudes, or .2 per year over the South
    Pole).

    <p>

    Radon in the basement, on the other hand...
     
  25. That was 200 counts per second, Skip. Only a factor of 60 difference!
    I turned up two more hot lenses with the geiger counter. A Schneider 135mm f/9 Repro-Claron (Not the G-Claron), and a 55mm f/1.8 Pentax SMC Takumar. Both were low energy emission and not much to worry about.
     
  26. Struan,

    <p>

    Thanks for the info. I've been wondering what the proper method for
    affixing and Aero-Ektar to the cat was.
     
  27. Just take a look at what is being sold on Ebay. Those
    Rodenstock Heligon lenses come out of Xray machines, not
    process cameras.
     
  28. No worries John, just remember that it's kinder to shave the cat
    first.
     
  29. dsdfsfd
     
  30. Looks as this one has had a fair dose of Roentgen! ;-)
     
  31. I trade WWII Aero lenses, all from the US Army Corps, 1940's, mainly
    Kodak, my favorite that I use with my Calumet is a 12"/5.0 Aero-
    Anastigmat, I also have a 12"/2.5 and a 13"/3.5, and a dozen Copying
    Ektanons and Copying Anastigmats, they don't glow green in the dark
    though, but I'm wondering if the risk is high enough to just toss
    them, or if there is no risk at all. I keep them all downstairs in
    the basement. Comments?
     
  32. Folks,

    <p>

    I just saw the thread, so I'm late. I do radiation protection for a
    living, and have for about 27 years now. The radiation protection
    field is based on the simple principle that no radiation exposure is
    acceptable without a corresponding benefit. Here, this means
    enjoying the benefits of a good lens.

    <p>

    The radiation levels associated with most lenses are relatively low
    compared to other consumer products and activities people perform.
    The human body has about 250,000 dpm of radioactivity, mostly from
    naturally occurring potassium-40. If you're worried about lenses,
    you should never, ever, consider flying since cosmic radiation
    levels go up as a function of altitude (10 mrem or so per flight,
    avg). Living in Denver for a year will expose you to many, many,
    times the yearly dose than being around most lenses. Oh, and get rid
    of those smoke detectors. Smoking adds 1-5 rem per year from
    radioactive lead which is a decay product of uranium and is
    concentrated by the plant. If you smoke, forget about lenses. The
    average dose per year is about 360 mrem, from nature in general.
    Fiestaware (the old orange stuff) was coated with uranium oxide and
    vaseline glass was also colored with uranium. So is dental
    porcelain (the uranium makes your dentures match your teeth under
    all types of light). Exposures from lenses would be miniscule
    compared to the sources above.

    <p>

    Thorium (and other rare earths like lanthanum) generally comes from
    monazite sand deposits, so don't worry about lenses if you live in
    Rio de Janerio, Kerala India, North Jacksonville Beach, or a large
    portion of the southeastern US coastal plains. The White Mountains
    in New England also have significant thorium so don't live there
    either. The southwestern US has a lot of uranium, so forget living
    there too. Not much left, is there?

    <p>

    The US Nuclear Regulatory Commission (and I assume the Brit's
    corresponding rulemongers) places restrictions on radiation levels
    from consumer products, and it used to be about 3-1/2 mrem per hour
    which would very roughly translate to 10,000 dpm with a geiger
    counter. The National Committee on Radiation Protection and
    Measurements (NCRP) has a publication on radioactive consumer
    products which is a nice read if you're interested. You should be
    able to find it in most good libraries.

    <p>

    Don't think old lenses are less radioactive. The daughter products
    are constantly replenished from the thorium parent, which has a half
    life of billions of years. However, if you want some real
    perspective, take your geiger counter through an antique shop and
    check the glass and glazed ceramics!!
     
  33. I too am late to this thread, but read its contents with great
    interest and amusement. As a radiologist, I am particularly impressed
    with the last response which is very informative. In all this
    discussion (some of it erudite), it is worth remembering that we bask
    in the life giving radiation of an enormous and self-perpetuating
    thermonuclear explosion i.e. the sun. As for 'no safe dose of
    radiation', without it we would'nt exist in the first place.I really
    would'nt worry too much about some old lenses.
     
  34. I *still* haven't made the measurements on my Aero Ektar, but
    Mikael Briggs has some worthwhile information here:

    <p>

    http://home.earthlink.net/~michaelbriggs/aeroektar/aeroektar.ht
    ml

    <p>

    Mine now lives in the cellar rather than my camera cupboard. My
    wife wants me to get rid of it, but where else can I get a lens that
    burns bugs so spectacularly?

    <p>

    Incidentally, I read on usenet that at least some of the colour
    centers in some of the radioactive lenses can be bleached by
    leaving the elements exposed to sunlight. If you are using these
    lenses and want to get close to their original performance, this
    might be worth a try.
     
  35. Anyone tried these kind of tests on 35mm lenses? I have an FD 35/2
    that's yellow and somwhere I read thorium was used in the glass, the
    lens construction is awesome, but I was concerned about the possible
    dangers, and if there's any possibility to get the originalk tint
    back. thanks
     
  36. A late addition to an interesting subject. (I'm a Ph.D. radiochemist by the way and the Radiation Safety Officer for our company)

    With the exception of the thorium glasses, we are talking about VERY LOW fields here. I'm routinely involved in nuclear medicine scans where patients are administered safely and routinely much larger amounts of radioactivity. These scans result in less dose than a chest X-ray to put the safety into perspective.

    The thorium glasses I hear are on the order of 1.5-2.5 mR/h which are low, but by no means insignificant. Do take care to limit your contact exposure to the lens (time, distance) and I wouldn't store it next to any boxes of film!

    If you are interested and have money to spend, check out Aware Electronics at http://www.aw-el.com/ These guys can hook you up with a nifty little thin window Geiger Muller counter for $150. You can use it to monitor Radon levels in your basement when you're done with lenses if you rig it up to a PC ;) I've recently designed a radiation safety system based on these little pocket GM tubes and they work very well indeed. I think I'll put one in my pocket next trip to the camera shop ;)
     
  37. As an illustration, an autoradiogram of some radioactive lens cells that I did recently out of curiosity. I placed the back cells of the three Repro-Clarons I own (355mm, 210mm, 55mm) directly on a TMAX 100 Readyload envelope for 19 days, with the convex element (the hot one) towards the film. Since the lens is symmetric, the front cells would work too, but the mount is deeper and would have increased the distance from lens to film. The film was developed for 14 min in TMAX RS 1+9 at 24°C (75F) (about N+1 1/2 for me). The visible effect is apparently dependent on the focal length, most probably because the lens element volume scales with the focal length, so the 355mm has the strongest effect, the 210 shows less density, and the 55mm does not show a visible effect. Anyway, it is probably not a good idea to keep film and these lenses in close contact for extended periods of time (or carry them in your pocket).
    004Kdy-10870584.jpg
     
  38. Hi all
    I just came across this thread and read it with interest.
    I was supprised by the number of people here that did not know about this problem.
    You will find this has long been known to users of 35mm format Pentax Super-Takumars.
    The main culprit in this regard is the early eight element 50mm f1.4 Super Tak, which I used to own myself and has Radioactive Thorium glass elements.
    I only had mine for about a week and got rid of it quick so hopefully I did'nt suffer too much damage to my DNA!
    Actually radiation was'nt the main reason why I got shot of it quick, the main reason was it was totally useless WO so it could not fufill the purpose I bought for in the first place,..as a fast lens.
    The later 7 element 50mm f1.4 Super Tak was apparently able to dispense with the need to use radiactive elements so that particular lens should be ok?
    However, trying to tell if its the new or the old model BEFORE you buy one is the hard part!
    Anyway I noticed a few users here asked how to cure the yellowing of the Radiactive Thorium glass elements...its actually very easy.
    Buy yourself a UV lamp and place it in a housing large enough to hold the bulb and the lens. "Bathe" the lens in UV like this for about 1 week continuously and this should cure the yellowing.
    Now I wonder if my Taylor-Hobson 12" f4 is safe?

    Regards

    Alf
     
  39. Um, Alf, I have two (2) of those 12"/4 Taylor Hobson telephotos. Long story. Anyway, AFAIK they don't contain radioactive glass.

    Taylor Hobson f/9 tessar-type process lenses are something else again. I have three, badged, respectively, Cooke Copying Lens, Taylor Hobson Copying Lens, and Apotal. All three had yellowed rear cells when I received them, all cleared after nearly two months under a 20w BLB fluorescent tube. I wouldn't carry any of them in a pants pocket.

    Don't worry, be happy,
     
  40. Oh no, I just bought that very same lens at a thrift store for two dollars. Very interesting and enlightening information.
     
  41. If this level of radioactivity is disturbing then there is more disturbing fact:
    If your weight is 70KG then:
    There are 500 decays per second of Potassium-40 in your body that emits GAMMA RADIATIONS.

    There are 3,900 decays per second of Potassium-40 in your body that emits BETA RADIATIONS.
    The Carbon 14 inside your body emits 3,700 Beta radiations per second

    Source:
    http://www.physics.isu.edu/radinf/natural.htm
    http://www.rerowland.com/K40.html
     

Share This Page