Identifying Radioactive Lenses
As part of my quest to find compact lenses that will work on my Sigma cameras. I've been looking at M42 lenses, I know many of which have radioactive glass. I know that they are generally considered safe to use, but my issue with owning one is the storage. I've read that storing them about 3 feet from any place you spend a lot of time is a good rule of thumb, but due to the layout and small size of my apartment that really isn't possible. So I think it's best that I just avoid them entirely for now. That being said I am having a hard time finding definitive answers on which lenses are and aren't radioactive. The lens I am currently looking at, a Pentax 35mm f/2 Super Takumar actually has conflicting information, some people claim they are, and some say they are not others say that it depends on which generation you get, but no one has anything conclusive. At least in my googling I haven't been able to find a really definitive list. I have found this, which seems to indicate it's not, but who knows how accurate it is:
https://camerapedia.fandom.com/wiki/Radioactive_lenses
I can't help you with determining which lenses are radioactive, but I watched this video by Simon's Utak a while ago and remember thinking it was very informative.
I think the falloff of the radiation intensity follows the inverse square law, one over the distance squared, so just a little bit of distance helps a lot. And any thick material you place between the lens and you helps too. I'd be more worried about putting it to my face over time. But if I recall in that video he shows even the camera body greatly reduced transmission to safe levels, and often only the rear element is radioactive too. Don't quote me on that!
Quote from JBP on February 16, 2024, 5:44 amI can't help you with determining which lenses are radioactive, but I watched this video by Simon's Utak a while ago and remember thinking it was very informative.
I think the falloff of the radiation intensity follows the inverse square law, one over the distance squared, so just a little bit of distance helps a lot. And any thick material you place between the lens and you helps too. I'd be more worried about putting it to my face over time. But if I recall in that video he shows even the camera body greatly reduced transmission to safe levels, and often only the rear element is radioactive too. Don't quote me on that!
I think I watched this video awhile ago actually, and just skipping through to the storage part I think he is were I got the 3 feet rule from, but yeah it sounds like I can't really comfortably store them. It would either wind up near my bed, near my food, or near my desk and none of those are particularly appealing to me.
Quote from photography.cory on February 16, 2024, 6:47 amQuote from JBP on February 16, 2024, 5:44 amI can't help you with determining which lenses are radioactive, but I watched this video by Simon's Utak a while ago and remember thinking it was very informative.
I think the falloff of the radiation intensity follows the inverse square law, one over the distance squared, so just a little bit of distance helps a lot. And any thick material you place between the lens and you helps too. I'd be more worried about putting it to my face over time. But if I recall in that video he shows even the camera body greatly reduced transmission to safe levels, and often only the rear element is radioactive too. Don't quote me on that!
I think I watched this video awhile ago actually, and just skipping through to the storage part I think he is were I got the 3 feet rule from, but yeah it sounds like I can't really comfortably store them. It would either wind up near my bed, near my food, or near my desk and none of those are particularly appealing to me.
Ah I somehow missed that 3' part of your post. I can see why you'd hesitate. For me personally I would think it's probably safe but it would always be on my mind. If I start buying potentially radioactive lenses I think I'd pick up a Geiger counter as well out of curiosity and also to test my storage method. Then again, how do you put a lens to your face that makes your Geiger counter *click click click* without anxiety? haha
Yeah if I decide to starting picking them up, I will probably grab a Geiger counter just to check them. I called KEH yesterday and asked if they kept notes on the radioactivity of the lenses they sold and they don't. So I suppose I could buy them, check them and return them if they are.
Hi Cory!
I saw this thread and wanted to give a little reply to help you understand the dangers, (and the lack thereof in most cases of these lenses) So over the years I've collected quite a few antique M42 lenses, and quite a lot of these have the thorium coatings. The thorium only emits alpha rays, which cannot go through skin in most cases, there may be some unique exceptions but you'll likely be safe. Another thing is that putting a cap on the lens is almost always enough to stop most emissions. I worked with an older photog who did a lot of his work on these lenses and he put it super well I think when he said,
"the only way to hurt yourself with these lenses is to hold the rear element up to your eye for hours and after all that the worst that will happen is cataracts".
Generally, these are not a health concern and you likely have more dangerous cups and plates hanging around the house.
I hope that will maybe put you at ease!
Quote from HeggenDazs on February 17, 2024, 5:29 pmHi Cory!
I saw this thread and wanted to give a little reply to help you understand the dangers, (and the lack thereof in most cases of these lenses) So over the years I've collected quite a few antique M42 lenses, and quite a lot of these have the thorium coatings. The thorium only emits alpha rays, which cannot go through skin in most cases, there may be some unique exceptions but you'll likely be safe. Another thing is that putting a cap on the lens is almost always enough to stop most emissions. I worked with an older photog who did a lot of his work on these lenses and he put it super well I think when he said,
"the only way to hurt yourself with these lenses is to hold the rear element up to your eye for hours and after all that the worst that will happen is cataracts".Generally, these are not a health concern and you likely have more dangerous cups and plates hanging around the house.
It does help put me at ease, especially if lens caps are sufficient to block most of the particles. I would probably still get a Geiger counter to double check, but if that's the case then it shouldn't be a problem to store them.
Quote from HeggenDazs on February 17, 2024, 5:29 pmHi Cory!
I saw this thread and wanted to give a little reply to help you understand the dangers, (and the lack thereof in most cases of these lenses) So over the years I've collected quite a few antique M42 lenses, and quite a lot of these have the thorium coatings. The thorium only emits alpha rays, which cannot go through skin in most cases, there may be some unique exceptions but you'll likely be safe. Another thing is that putting a cap on the lens is almost always enough to stop most emissions. I worked with an older photog who did a lot of his work on these lenses and he put it super well I think when he said,
"the only way to hurt yourself with these lenses is to hold the rear element up to your eye for hours and after all that the worst that will happen is cataracts".Generally, these are not a health concern and you likely have more dangerous cups and plates hanging around the house.
From a previous post of mine:
Incidentally, I have a connection where the lens got tested (I don't want to say where) with equipment not available to the public. The guys who tested it went above and beyond what I asked, I think they found it really interesting. The lens is giving off alpha at levels consistent with what you read on the web. It's also emitting small amounts of beta and gamma. Really small but above background.
No measurable radiation could be detected from the front of the lens. All the readings were tested from the exposed rear element 1/4" away.
They also figured out that in addition to thorium, the glass has traces of radium and potassium. If I remember right the radium was emitting beta and the potassium, gamma.
Still, having a history of cancer in my family, I question how anyone really knows how safe it is.
Plus, there is the unlikely but still possible situation of breaking the lens indoors.
