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Post by vintageslrs on Jan 17, 2006 13:36:27 GMT -5
Litesong...
So your Fujinon EBC !.4 lens has some yellowing. Ok, I think for the time being we can assume it is at least "warm". I am very anxious to receive my testing equipment and to begin some testing. It is an interesting subject and perhaps one in which we may be able protect our health with some knowledge and prudent behavior.
Bob
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Post by John Parry on Jan 17, 2006 15:41:10 GMT -5
Please people....
The levels you are talking about are miniscule... Some of the lens manufacturers used Thorium for a time as it gave the glass a much better refractive index than ordinary lead (some varieties of which are also radioactive btw). Eat a pound of Brazil Nuts, and you will have ingested a far higher internal dose than you will ever get from any commercial camera lens (Brazil Nuts contain large quantities of Radium).
If you happen to have an uncoated lens, dissassemble it, and put it the elements into the oven at maximum temperature for a couple of hours. The yellowing will have disappeared. Sellers of crystals do the opposite - they put crystals close to a radioactive source to obtain smokey quartz from clear quartz. Put smokey quartz into the oven and - bingo - it turns clear.
John
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Post by kiev4a on Jan 17, 2006 17:19:25 GMT -5
John: Well said.
Once I had the opportunity to vist the Idaho Nuclear Laboratory in Arco. Stood on the edge of a "canal"--a concrete-lined ditch maybe 10-12 feet wide and 30-feet deep. The canals run from the nuclear reactors to storage areas for radioactive materials. When they replace the rods in a reactor cores, they drag them along the bottoms of the canals with 30-feet of absolutely chemically pure water as a shield. It is so clear you can look down into the canals and see the rods -- several inches in diameter and at least 10 feet long on the bottom, giving off a greenish glow. Now that's the sort of radiation you wouldn't want to have hanging in an ever ready case from your neck! Sorry if I offended someone with attempts at humor on this topic in an earlier post but the amount of radiation we're talking about in lens glass is insignificant. I would be surprised if some of the old radium dial clocks gave off more.
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Post by vintageslrs on Jan 17, 2006 17:47:44 GMT -5
John
you say the amounts are miniscule...OK you are welcome to your own opinions. As am I....and I feel that some lenses with a reading of 12 times what is normal or in the case of some F1.4 lenses--it could be in the area of 100 times more than normal .......miniscule or not...I wish to be prudent about handling, using and storage...call me a worry wart or alarmist...but like my father used to say.....(us being 100% Sicilian) "Sausage his own", a comical rendition of to " to each his own". you please do as you see fit. And I would hope others will also. I will decide what course I wish to follow after I see for myself what kinda of readings I get after doing my own testing.
be well.....have fun
Bob
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Post by herron on Jan 19, 2006 16:31:37 GMT -5
...If you happen to have an uncoated lens, dissassemble it, and put it the elements into the oven at maximum temperature for a couple of hours. The yellowing will have disappeared. John I read somewhere you can do the same (eliminate yellowing) by putting the lens in the sun for a day or so. I would have to go that route, since my better half (interesting description, since I easily make more than two of her!)...anyway, she does not take kindly to my camera stuff in her kitchen! As to radioactivity, I guess each of us has to decide what it all means to us personally. I'm not taking it lightly, but I've been exposed to enough x-rays and MRIs in the past several years to glow in the dark anyway!
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Post by vintageslrs on Jan 23, 2006 19:28:28 GMT -5
OK. Preliminary results concerning radiation and camera lenses are in.....primitive and imprecise as they are...but they are in....anyone wishing to receive this info....
email me privately @ bob40caliber@yahoo.com
Bob
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Post by lulalake on Jan 24, 2006 21:54:54 GMT -5
Bob, Thanks for this thread. I think I'll pass on Takumars. I do have one of those Ukranian lenses, a Hartblei Super Rotator 45mm lens for my Mamiya 645AFD. (It was built after Chernoblyl also. I think I will figure our somewhere in Austin to have it geiger countered. I know it's a long shot but would you have any suggestion as to where one could get geigered? a Hospital?
Thanks
Jules
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Post by vintageslrs on Jan 24, 2006 22:31:41 GMT -5
Jules
Before you do anything you may wish to email me privately for "MY" research info.
bob40caliber@yahoo.com
Bob
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135mm
Contributing Member
Posts: 10
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Post by 135mm on Oct 11, 2009 10:04:46 GMT -5
October 2009, I have just read the 3 pages of this thread. Now 3 years on is there any update on this, are we still "at risk" so to speak? Or what? 135mm Mike.
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Post by pompiere on Oct 12, 2009 16:00:10 GMT -5
I am not sure where the OP found his data, but for most locations in the United States, the average annual background radiation from naturally occuring sources is around 2.4 millisieverts. The annual limit for radiation workers in the United States is 50 millisieverts, a numbers chosen to be low enough that no new cancer cases occur outside of the statistical norm. Most companies have administrative limits that are much lower than that, in order to make sure that no workers exceed the federal limit. The OP seemed to be focused on the fact that anything that was measurably higher than "normal", was really bad. The bottom line is that if his measurements were accurate, then they are so low that they should not pose any threat to your health. Assuming that he meant 12 microsieverts per hour for the "hottest" lens in his list, you would have to carry the lens in your pocket for 11 hours a day, 365 days a year to approach the 50 mSv federal limit. Time, distance and shielding are the buzzwords for dealing with radiation. Less time, more distance and more shielding will reduce the exposure. I wouldn't sleep with a radioactive lens, but I wouldn't be afraid to use it. I don't own any of the lenses in question, so I can't verify the measurements, but I work at a nuclear power plant, so I do know a bit about radiation.
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Post by Peter S. on Jan 19, 2010 16:03:19 GMT -5
Hi there,
haven't read through the whole thread, and don't have enough time to visit often... but anyway - this is what I found out so far:
- for the more mundane lenses we typically use here (e.g. the F/1.4 early pentax lenses and some Rokkors, 2.5/28, early 1.2/58 and early 1.7/85) it still isn't clear whether some amount of unclean rare earth (i.e. undesired radioactivity) or thorium oxyde (i.e. planned radio activity) is the source of the radioactivity. For a thorium containing lens (e.g. the Kodak Aero-Ektars) one would expect a lot of radioactivity, while for some rare earth ingredients that contain a fraction of active isotops a lower amount of activity can be expected. I still think by myself that the usage of Thorium might have been to promising for the designers to resist...
- there are two major ways to cure the damaged structure of the glass: exposing to UV (sunlight, UV-curing lamps, exact wavelength and intensity still not exactly known) or heat. Heating will require to use at least 150 .. 200°C for several hours. Exposure to sunlight will require a few weeks up to a few month. I have cured two MD W. Rokkor 2.5/28 with an over-weekend exposure to an UV curing lamp, which took place in a locked lab, as the UV radiation is pretty hazardous.
- in the German Minolta Forum we currently discuss to measure some of the mentioned lenses most probably at the univerity of Ulm, Germany. I am _very_ curious on the outcomes, and I agreed to supply my two 2.5/28 and a yellow 1.2/58. But the test hasn't started yet. Forgot to mention, that any isotope got a unique finger print when measuring the gamma spectrum of the radiation. So we can be sure to find out what's inside the lenses.
Best regards Peter
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Post by nikonbob on Jan 20, 2010 6:50:43 GMT -5
Peter S
Could you let us know the results of the testing?
Bob
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Post by alexkerhead on Jan 20, 2010 23:56:57 GMT -5
With all my Pentax 1.4/50 lenses laying around, there is no wonder I grew a third...ummmmm nevermind.
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SidW
Lifetime Member
Posts: 1,107
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Post by SidW on Jan 27, 2010 18:59:22 GMT -5
Further to what Pompiere wrote above. If anyone is really worried, then keep your neckstrap short and don't wear your camera back to front, with lens pointing towards yourself. Low slung cameras are out in this context. But no-one takes even these low levels lightly, not Pompiere, and not Peter S (who showed how careful he was with the UV light). So yes, we'd all like to see the results of measuring lens radiation. But those of you who are already convinced there's a hazard will have already seen overwhelming evidence in the form of reel after reel of film spoilt by radiation. Or have you? We're all reluctant to have our films checked for a fraction of a second at the airports, but we happily leave a radioactive lens on the camera for months. All lens radiation has to pass through the film before it reaches the photographer's body. Unless, of course, you wear the camera back to front.
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Post by John Parry on Jan 28, 2010 17:41:39 GMT -5
Has anybody actually had any films fogged by airport x-ray machines recently? I know the equipment is far more sensitive, but I never found any problems 20 years ago when the machines relied on brute force and sheer power.
Regards - John
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