Radioactive Lens on a Mamiya Sekor Camera Lens

Geiger counter shows some radioactivity in the lens of this Mamiya Sekor. The lens glass probably contains Thorium. I would think twice about holding the lens up to my eye. Thorium emmits alpha beta and gamma radiation.

Thorium raises the refractive index and lowers the dispersion of the lens.
http://en.wikipedia.org/wiki/Thorium

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[Ex0th3rm1c]

what you are picking up there is background radiation buddy. also i think your counter needs to be calibrated

[JakesOnline]

You are wrong about the background radiation. When the needle stays at zero, then goes crazy near the lens it's pretty obvious. I never claimed it was calibrated. This counter was designed for gamma only. I removed lead foil from the GM tube and drilled holes in the aluminum to allow beta detection. I might post a video of Civil Defense counter reacting to the lens..

[Ex0th3rm1c]

I don't know what meter your looking at but in that video, the needle barely moves, and i hear like one or two clicks. Also, that modification you're talking about could have destroyed your detectors.

[JakesOnline]

There's no sound coming from the meter, it's debri on the granite when I slid it over to the camera, it does sound like a geiger click. You must be blind, but that's ok, your're inspiring me to make another video to prove it works.. Yes the mod could have destroyed the meter, but it didn't because I know what I'm doing. I drilled holes in the aluminum case near the GM tube.. I guess I could have been more clear about the mod.

[tonofshit]

Hey, that's cool!!! Is that a really sensitive meter?

[JakesOnline]

Seems to be, but I don't have anything to compare it to.

[DrD0000M]

Hmm...so is the granite countertop radioactive too? Some pieces of granite have been found to emit dangerous levels of radon.

[maxfeklin]

хаха. улыбнуло =)

приезжайте на Урал и удивитесь что это норма!

[warut822]

Remove the lens from the camera and put the Geiger counter near the rear end of the lens. This way you'll likely get a higher readout because the thoriated lens element is usually a rear one.

[SharloNoir]

I just got a mamiya/ sekor 500 TL

AHHH I was so happy but damnnn radioactive??!!

zats terrible. can thisssss be dangerous??

wat could happen???:O :O :O

[008626]

barely seems radioactive at all - i don't know how sensitive your geiger counter is, but i'm pretty sure my uranium marbles are more radioactive than that lens

[rakitov]

I bought takumar 50mm f1.4... It is with thorium, too. I will send it back.

[sciencoking]

if you think this is strong come to me

my autunite will make your needle spin!

[Polybun]

This is actually a well known thing, and a problem. Several early pentax lenses used a similar radioactive coating. Your correct in thinking it is thorium. It actually causes the lens to yellow over time if not exposed to ultraviolet light. It can take several weeks in the sun to bring them back to clear.

[Ex0th3rm1c]

Ah oh my hahah. This is embarrassing. Sorry about all that, I see what your getting at.