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?
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?
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.
Dont't worry, be happy!
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!
Hi Andrea! Thanks for the tip on Pentax lenses getting yellow because of lens ce ment. You say it can be fixed? Can you give me some information and tell me if the price of such repair is not proh ibitive?
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.
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.
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.
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.
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.
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 :-)
I'll try to answer as many points as I can.
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.
Geoffrey, I'll check again, but I'm sure it was 200 counts/second.
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.
The Aero Ektar used Thorium, not Lanthanum in the glass, and this is the reason why this particular lens is such a 'hot' property.I'll investigate lenses containing Lanthanum, if I can get hold of any, but I don't think they'll be as bad.
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.
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.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!)
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?
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.
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.
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.
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.
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.
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.
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 bedroo m. Shall I consult an oncologist or go directly for the mute? Kidding set aside, are they any precautions worth t aking?
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.
If you want to be certain, find your local radiological protection officer and ask. He or She will be in the phone book.
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.
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.
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.
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.
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.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.
Update!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.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.
A Kiev Mir-24N 35mm f/2 that I thought might be hot turned out to be completely clean.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.
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