Radioactive optical glass?

[Steffen]

On the use of thorium oxide in camera lenses and eyepieces:

http://camerapedia.wikia.com/wiki/Radioactive_lenses

Who's got a Geiger counter? :atom:

Cheers
Steffen.

[GrahamL]

I've bumped a few cameras in pawn shops with T glass but never seen a lens yet,I've got a couple of early mc rockers that are sure on the right time line but still aren't made with it .


never heard of eyepieces though , wonder who made em?

[Barrykgerdes]

Thorium has been used in many devices to increase its emission properties for years. I don't know what its effect is in camera "glass" but it must have some useful effect. I don't think the stray radiation will be a problem (even if it is noticeable with a Geiger counter)

Barry

[Wavytone]

Wouldn't be surprised if lanthanum eyepieces are slightly radioactive too. (Vixen LV's, LVW's, NLV, TV Panoptics...)

There was a big military Erfle eyepiece - monster of a thing which Surplus Shed used to sell - which certainly did have radioactive glass in it. The element had a tendency to turn brown, if I remember correctly. And I had two of the Pentax lenses listed back in my film SLR days.

I'm not sure whether the "healing" trick works, it sounds a bit far-fetched IMHO, like Pyramid Power.

[Barrykgerdes]

Thorium has been used in many devices to increase its emission properties for years. I don't know what its effect is in camera "glass" but it must have some useful effect (I suppose I could look it up under google). I don't think the stray radiation will be a problem (even if it is noticeable with a Geiger counter)

Barry

[Terry B]

I must admit that I had wondered about the glass on the front of my SBIG CCDs.
The number of "cosmic ray" hits that I get with my ST10XME is vastly higher than my ATIK camera. I know they are different CCDs but this shouldn't be a major factor. Also my home made genesis CCD with a kodak 0401E chip that is similar to the kodak ones in my SBIG cameras has very few CRH.
Does the cover glass emit small amounts of radiation?

[Barrykgerdes]

I googled Thorium and the wikipaedia mentioned its effect on glass in cameras and lenses as a means of increasing its refractive index.

Barry

[multiweb]

Bin those lenses... no good for astro. You'll get a green glow and gradients in your subs. :P

[wasyoungonce]

Most Thorium coatings are weak alpha emitters.

Reasonably safe as long as your not licking them 24/7 or breaking the lenses.

But I am surprised they can be found in non military glass!

[Peter.M]

La 138 is not very abundant naturally and decays via electron capture so I wouldn't think you would measure any radiation from an eyepiece. Regardless neutrinos should not be damaging as they pass through your body.

[AdrianF]

I have put thorium in my mouth deliberately and except for the weak green glow on really dark nights and the tics it hasn't affected me at all ��
I am a boilermaker who specialises in GTAW and use Thorium and cerium impregnated tungstens daily

Adrian

[multiweb]

Sooo.... do you use your bare hands to take flats at night? ;)

[Shark Bait]

It is amazing how much specialist military gear glows in the dark. :)

Would you like some Tritium with your Thorium?

[wasyoungonce]

No Depleted uranium pls......!:rofl:

[peterl]

Have been using my radio active super takumar 50mm 1.4
lens for outdoor and milky way shots for years and no problem with any exposures from it.One of my best lenses!! It has the typical yellow rear element.
It stays in my camera bag away from me. :)

Peter.

[RobF]

Good that the article talks about relative radiation from xrays and airline flights. The reality is outside of a foot from the lens you'll be getting much less exposure than during an airline flight. Then again, I s'pose you wouldn't get many alpha particles through the skin of an airliner!

[Barrykgerdes]

Years ago we all wore luminous hand wrist watches until we were warned off because of the radiation. How many people developed cancer of the wrist as a result. I know of none but that may not be a true picture. Although the people who painted the luminous material on did suffer some nasty problems.

Thorium is a radioactive element that is used extensively in industry and has been used for many years to enhance many substances. Luckily it does not present a serious radiation risk in the manner it is used. An unstated property of glass is that it actually shields from the radiation.

Barry

[naskies]

They're gamma ray emitters too; this particular Takumar Super 50mm f/1.4 lens was found to emit 0.48 mrad/hour at the lens surface (mostly shielded by the camera back):

https://dl.dropboxusercontent.com/u/13644418/iis/Radiat%20Prot%20Dosimetry-1983-Taylor-187-8.pdf

As the original article points out, if you're using it as a lens and/or handling it for short periods of time it's no worse (less, in fact) than the radiation that frequent fliers get in the air.

In the worst case scenario, i.e. doing something silly like wearing the lens element as a necklace 24/7, the yearly dose you'd get is 44 mSv of gamma radiation - which is below the maximum dose for US radiation workers. xkcd has a great chart showing relative doses:

http://xkcd.com/radiation/

That said, if it were me I'd personally avoid using thorium lenses because there are non-radioactive equivalents readily available, and I plan on working in hospitals and catching lots of flights during my lifetime.

Interestingly, there's a lot of evidence that mild doses of radiation are actually protective against cancer and radiation sickness for many animals :lol:

[Miaplacidus]

Don't worry. The difference between man-made sources of radiation and normal background is getting smaller all the time...

:rolleyes: