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04-30-2012, 06:56 PM   #16
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QuoteOriginally posted by ultraviolet Quote
Check this out then find it out from the above chart.
No idea what the equivalence is between those counts per minute and the chart, in µS, but the clicking sounds scary. Just for caution will store the soviet lenses (much more glass than that 50) a bit further from my bed from now on.

04-30-2012, 07:18 PM   #17
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QuoteOriginally posted by c-meier Quote
No idea what the equivalence is between those counts per minute and the chart, in µS, but the clicking sounds scary. Just for caution will store the soviet lenses (much more glass than that 50) a bit further from my bed from now on.
Most soviet lenses are not radioactive, the only confirmed one I've seen is an Industar 61L/Z for SLRs and the 61L/D for rangefinders. By far the most common radioactive glass is Pentax Takumars.
04-30-2012, 07:52 PM   #18
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Here is an interesting set on Flickr that includes measurements from many different lenses from various makers.

Radioactive Lenses - a set on Flickr

Of the top five, the highest radiation at 100 mm distance was from a Canon FD 55/1.2. Also in that group were lenses from Konica, Mamiya/Sekor, Fuji, and Pentax. Interestingly the ST 50/1.4 was used as the standard and the Canon was almost twice as hot!


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05-01-2012, 01:52 AM   #19
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QuoteOriginally posted by elliott Quote
Most soviet lenses are not radioactive, the only confirmed one I've seen is an Industar 61L/Z for SLRs and the 61L/D for rangefinders. By far the most common radioactive glass is Pentax Takumars.
Oh. Ok. No idea why I was under the impression some of my lenses could be radioactive, in particular the Jupiter 37A. Now that I think of it, it isn't even the MC version.

05-01-2012, 07:10 AM   #20
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Yes, it is very dangerous -- if you grind it up and eat it.
05-01-2012, 07:17 AM   #21
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Neh, it's not dangerous. It only has advantages. Because of my healthy fluorescant glow, I can now read in the dark.

Sorry, I couldn't resist.

The radiation level of the Taks is so low, that it doesn't even show up on the generic detectors at airports and harbours.
05-01-2012, 08:13 AM   #22
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QuoteOriginally posted by RioRico Quote
Yes, it is very dangerous -- if you grind it up and eat it.
But having ground glass in your digestive system is probably a bigger immediate danger than the radioactivity.
05-01-2012, 09:03 AM   #23
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As I recall what little I know from USArmy health physics, eating the ground up lens wouldn't represent much hazard (it'd pass through too fast to do much radiation damage); like most alpha emitters, thorium is a hazard when inhaled deeply into the lungs. For deep penetration into the lungs, quite small particle sizes are required; like smoke or fog, - small enough to float in air - normal "ground glass" particle sizes are too big to represent much hazard.

Seriously, don't worry about thorium as part of glass.

05-01-2012, 11:44 AM   #24
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QuoteOriginally posted by newarts Quote
like most alpha emitters, thorium is a hazard when inhaled deeply into the lungs.
Thorium emits both alpha and gamma. The link I cited above measured gamma...

As noted in many places, the radiation is weak enough so that fogging of the film is not an issue. That being said, there is a geniune concern where this type of glass was used in oculars for binoculars and such.


Steve
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