[Iivan]

Hi!
I just bought a beautiful Asahi Pentax Spotmatic with a Super Takumar lens (55/1,8). The camera shop said that these lenses are treated with Thorium and are somewhat radioactive. Does anybody know should this be a concern for your health?
best regards
Iivan

[RioRico]

Fear not. No hair will fall out. No children will mutate. No goldfish will glow. How radioactive are they? Consider that nuclear radiation was first detected by placing radioactive ores onto photo paper. After long exposure, the paper became fogged. Now consider that these lenses were designed to sit VERY VERY CLOSE to very sensitive film. And they don't fog the film any. See?

Producing such lenses now is prohibited, not because of what the materials would do to users, but because of risks to production workers. Sleeping with such a lens nestled against your body will expose you to less radiation that will eating a banana. Don't sweat it.

[newarts]

Thorium Facts - Periodic Table of the Elements

I'm not an expert in Health Physics but I think the following is true..

Thorium is an apha emitter hence is not very dangerous when melted into a glass or as part of any other solid material. Alpha particles have a very short range in materials (even air) so are usually blocked before causing cellular damage; they are dangerous when inhaled because then they are in close enough contact with cells to do damage.

Grinding a thoriated glass lens could make powder fine enough to float in air - that powder would be dangerous* if inhaled. Otherwise don't worry much.

*increase the risk of cellular damage leading to cancer.

[boriscleto]

Don't do this to your lens and you should be alright.

Brian Ayling's photographic repair tips

[woof]

Hi!
I just bought a beautiful Asahi Pentax Spotmatic with a Super Takumar lens (55/1,8). The camera shop said that these lenses are treated with Thorium and are somewhat radioactive. Does anybody know should this be a concern for your health?
best regards
Iivan

I have always beleived that none of the the 55 f/1.8's (going back to preset days) are on the list of thoriated or "rare earth" lenses. I may be wrong here. It appears that the Auto-Takumar f/1.8 55 used rare earth. This was the forerunner of the entire Super-Takumar line. See "Press text" for the Auto-Tak here: http://www.taunusreiter.de/Cameras/Pentax_Takumar_e.html If that is true, this mightn have been carried into production for the Super Takumars.

Additionally, I can confirm that the sales lit of the time also touted the 55 f/2.0 as having "rare earth." The f/2.0 was the same lens as the 1.8, just slightly crippled for down market. So if those lenses which ran concurrently with the 1.8 had thoriated elements, and were nothing more than f/1.8's with a different aperture ring, there is a good chance that at least some 1.8's are thoriated. This would be a bit of revelation from the standard list of lenses that are thought to have radioactive elements.

Some more info here. The list is pretty consistent overall with some exceptions. No exceptions for the f/1.8 lenses though.

Thoriated Camera Lens (ca. 1970s)
List of Takumar Lenses That Turn Yellow
Introduction of Thorium Oxide into Super Takumar Lenses::Manual Focus Lenses

Again, I can confirm from sales literature that the 55mm f/2.0 Super and SMC had "rare earth" elements and so are on this list. See for example Die Cast Pro - Asahi* Optical Super-Takumar 55mm f/2.0 which is transcribed from the sales literature.

It is clear here that these f/2.0 had "rare earth" elements. In contrast, "rare earth" is not mentioned here: Die Cast Pro - Asahi Pentax Electro-Spotmatic Index

I think to be safe, you assume this lens IS thoriated and treat it accordingly. (Which is to say DON'T hit it with a sledge hammer so that you might inhale some dust.)

woof!

[pxpaulx]

Grinding a thoriated glass lens could make powder fine enough to float in air - that powder would be dangerous* if inhaled. Otherwise don't worry much.

I've always stood by the philosophy of not inhaling ground glass too!

[Capslock118]

Firealarms are radioactive - that doesn't mean you should run away from them. The amount of activity is so low it's just academic to say firealarms are radioactive.

so...that said - are you going to be concerned? well, you shouldn't be.

[Ratmagiclady]

I've always stood by the philosophy of not inhaling ground glass too!

Very likely good policy, but that's *actually* why they stopped making such lenses, not cause of the consumer but because of the guys actually working in the optical plants where they *do* grind the stuff.

I've got a nice old Canon 35/2 and those are supposed to be fairly 'hot' as Thorium lenses go, (Really neat, though: *concave* front element , and like many of these old SC/SSC-style metal lenses, is *dense.* (It's not big, but it's got to be almost all glass in there, and the body's heavy, too: I know it when I'm carrying this. )


At the very moment in history, radiation badges are probably in pretty high demand, but if anyone's got one, I could always just see what it accumulates. If I recall, I believe it's supposed to be quite measurable, but not what you'd call a health hazard.

[jolepp]

Thorium-232 is an alpha emitter with remarkably long half-life (14.05x1E9 years) which means very low activity / mass. Besides, as mentioned, the alpha particles do not tend to get far before colliding into other matter losing their energy and thereby the ability to do harm. Kind of like small shotgun pellets, essentially harmless at a bit of a distance (but still deadly at closer range), only the scale of things is so much smaller that thorium would need to be, essentially, in contact to tissue to do harm.

Actually, it might be kind of cool having one of these

[Ratmagiclady]

Yeah. Actually, when I was younger, I used to really love those yellowed Super-Taks. No one ever actually told me why they were that way, (Clearly, no Internet back then, you knew what you *heard,* were told, or found out for yourself, and that'd be it. )


Still liked em, though. Just thought it was 'A Pentax thing.'

[Valdormar]

I never gave much thought about this topic. Such a low degree, I do not think anyone would be at any risk.

[monochrome]

I bet we get more microsieverts (there's a word I didn't know last month) from our cell phones in a day than we'd get over a lifetime from a Tak 50.

[jac]

Hi!
I just bought a beautiful Asahi Pentax Spotmatic with a Super Takumar lens (55/1,8). The camera shop said that these lenses are treated with Thorium and are somewhat radioactive. Does anybody know should this be a concern for your health?
best regards
Iivan

As you wrote this, you were being bombarded with radiation from sources both terrestrial and extraterrestrial. You most likely are currently being exposed to and absorbing radon gas emissions from the earth immediately below your dwelling in far greater amounts than any significant source of manufacturing including rare earths in Takumar lenses. Excuse the pun, but suck it up. You've been doing it throughout your lifetime.

[Ratmagiclady]

I bet we get more microsieverts (there's a word I didn't know last month) from our cell phones in a day than we'd get over a lifetime from a Tak 50.

Different kind of radiation, actually, ...the difference is real, but what your cell puts out isn't officially called 'radiation. ' Tidy, eh?

[jolepp]

... or, in a wider sense the visible light is radiation as well. I guess 'radiation' is commonly used as a shorthand of 'ionising radiation' that is, particles and quanta that are energetic enough to mess with the electrons minding their own business whirring around nuclei making them atoms. This, in turn means that the chemical bonds binding atoms to molecules (making up us) might get broken (and so by extension may we); chemical bonds are about the outermost electrons of atoms interacting in ways that result in more or less stable arrangements of atoms where in the stable ones the little darlings have arranged themselves in a way that takes some energy to change (and therefore does not happen all by itself).