Radioactive lens bad for camera sensor?

Mr Roygbiv rainbow said:

I would worry more about what makes Bananas than the lens , Sunshine !
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Roygbiv

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I would guess that levels of radioactivity varied from lens to lens...

http://www.youtube.com/watch?v=xeB_aL27chI

http://www.youtube.com/watch?v=OWgYhQnRcWM

http://www.youtube.com/watch?v=oL3D7FQTHXo&feature=related

Dave

Several points:

The original question was whether these lenses would affect sensors. Somewhere along the line the discussion became whether they are dangerous to users.

Presenting the facts, rather than simply repeating irrelevant facts, is not "losing track".

The radionuclide that would give you most of whatever dose you did receive from thoriated glass is Tl-208 (one of the daughters of Th-232) which has a half-life of 3 minutes. The half-life of Th-232 is irrelevant to determining the dose.

The dose from eating a banana is somewhere in the order of 0.1 microSv, so handling such a lens daily and eating a few more bananas a year would probably be comparable.

It may be an urban myth, but trying to de-bunk it with irrelevant points is likely to be even less successful than presenting more detailed arguments.

antoineb said:

let's not lose track too much here

there was an initial assertion that these lenses with some thorium glass were dangerous things

I think it's pretty clear by now that they're not, in the sense that even using one daily would contribute less exposure than eating a few more bananas a year.

So these lenses are not dangerous. They're not dangerous mostly because Th-232 has a very long half-life and thus is not very radioactive at all.

So it's your typical urban myth.

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--
Regards
Roger
http://www.pbase.com/rogerwilmot

Roger Wilmot said:

Several points:

The original question was whether these lenses would affect sensors. Somewhere along the line the discussion became whether they are dangerous to users.

Presenting the facts, rather than simply repeating irrelevant facts, is not "losing track".

The radionuclide that would give you most of whatever dose you did receive from thoriated glass is Tl-208 (one of the daughters of Th-232) which has a half-life of 3 minutes. The half-life of Th-232 is irrelevant to determining the dose.

The dose from eating a banana is somewhere in the order of 0.1 microSv, so handling such a lens daily and eating a few more bananas a year would probably be comparable.

It may be an urban myth, but trying to de-bunk it with irrelevant points is likely to be even less successful than presenting more detailed arguments.

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So you're saying that you get the same amont of radiation from a banana as you do from an x-ray?

You care to back that statement up?

"I was recently reading some previous postings and web articles about certain lens glasses containing radioactive elements, and wondered if any of my collection might be 'hot'.Initially, I was more curious than worried, but after doing some tests, I'm now definitely worried, and I think my findings deserve wider attention.

I have a sample of a 7" Kodak Aero-Ektar, which is a lens that has a big reputation for being potentially radioactive.However, all the articles I've read state that the radioactivity is mainly in the form of alpha emmission, and shouldn't give much call for concern, since alpha particles are quite low energy, and easily stopped by any solid object. I'm told that alpha particles can only penetrate about 40 microns into human tissue.Anyway, to cut to the chase: I just got our radiation protection officer to run a geiger counter and a dosimeter over the Aero-Ektar, and he found that the rear element was quite hot, giving about 200 counts/second.

Worse yet, we discovered that it was mainly GAMMA emmission, since even an inch of perspex and a steel plate hardly affected the counts at all. The active element used in making the glass is Thorium, and a quick check of the table of its decay products confirmed that they're mostly gamma emmitters, after about 6 years of decay.Dosimeter readings showed that within 1" of the rear lens surface, the dose was above the limit allowed for monitored radiation workers, and only fell to the publicly allowable safe limit at more than 6" from the lens.I don't think I'll be using that lens as a paperweight, or handling it too much from now on. By all modern standards, that lens would be classed as downright hazardous, and not to be used without protective clothing!I'll be testing the rest of my lenses as potential gamma sources as well in the near future."

http://photo.net/large-format-photography-forum/0035DS

U-tube video

http://youtubevideo.isgoodness.com/watch/video/id/OWgYhQnRcWM

The old lenses made back in the forties and fifties, had far more thorium than those made today, if they make any such lenses today. Nor am I making the claim that thorium is the same as plutonium - However, why someone would go out of their way to handle such material on a daily basis is beyond me.

Dave

for the rest, supposedly dangerous radioactive lenses are just an urban myth. Activity levels are so low due to the very long half-life of Th-232.

When there's a decay chain, the activity in that chain can only go as fast as the first step, in this case Th-232. it's like a waterfall, if it's the width of your little finger at the top, it can't be 300ft wife at the bottom.

like I wrong, the mere potassium (K-40) content in an adult human body, gives about 4'000 radioactive decays per second. And that's just from this source, and then you've got various other internal and external components.

Myth.

antoineb said:

Which brings us back to the OP: can such a think as "hot" (ie radioactive) lenses exist? I do not think so. And even if a mad nasty scientist purposedly installed a radioactive source on a lens, this would cause nasty damages to the photographer long before it caused damages to the camera's sensor.

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Whew! That's a relief!

antoineb said:

like I wrong, the mere potassium (K-40) content in an adult human body, gives about 4'000 radioactive decays per second. And that's just from this source, and then you've got various other internal and external components.

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From the article Dave (Chato) quoted, http://photo.net/large-format-photography-forum/0035DS , the 200 counts per second was for ionisation events detected by a Geiger counter.

You quote 4000 K-40 decays per second from the human body, but only a small fraction of these will be detected by a single hand-held GM tube. From such a diffuse source, little of the emitted radiation will strike the detector. Second, in a the tube is designed to respond to both gamma and beta radiation, the gamma efficiency is usually low, and any beta radiation needs to enter via a thin window, which is usually fairly small. http://en.wikipedia.org/wiki/Geiger-Muller_tube

For typical Geiger-Muller detector I would dispute that "200 counts a second is nothing". In my opinion, "Don't panic, close the lid, and put it back in the cupboard" would be more prudent. Of course, you may simply have a different approach to risk than my own (which in turn seems less cautious than Dave's) ;-).

Cheers.
--
Alan Robinson

antoineb said:

When there's a decay chain, the activity in that chain can only go as fast as the first step, in this case Th-232. it's like a waterfall, if it's the width of your little finger at the top, it can't be 300ft wife at the bottom.

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On this you are correct. The net activity depends on the rate of decay of the Th-232. After a few years the shorter-lived daughter products will be in equilibrium with the rate of Th-232 decay.

For every Th-232 decay, there will be 6 alpha particles, 4 beta decays, and roughly 4 gammas, if I have counted correctly. There is some variability in the gamma emission, depending on the precise decay path.

Cheers.
--
Alan Robinson

Chato said:

Roger Wilmot said:

The dose from eating a banana is somewhere in the order of 0.1 microSv, so handling such a lens daily and eating a few more bananas a year would probably be comparable.

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So you're saying that you get the same amont of radiation from a banana as you do from an x-ray?

You care to back that statement up?

Dave

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I'm not sure how you infer that I said this. I did say that a banana gives a dose somewhere in the order of 0.1 microSv. This link:
http://www.radiologyinfo.org/en/safety/index.cfm?pg=sfty_xray

suggests that a chest X-ray would give a dose of 0.1 milliSv. So 1,000 bananas equals one chest X-ray.
--
Regards
Roger
http://www.pbase.com/rogerwilmot

I think we are all agreed on this one. The point I was making was that, for the same activity, the dose from Th-232 is higher than from many radionuclides with shorter half-lives because of the strong gamma emissions from its short-lived daughters. So it is the assertion that "long-lived radionuclides don't give significant doses" that I am contesting.

alanr0 said:

antoineb said:

When there's a decay chain, the activity in that chain can only go as fast as the first step, in this case Th-232. it's like a waterfall, if it's the width of your little finger at the top, it can't be 300ft wife at the bottom.

Click to expand...

On this you are correct. The net activity depends on the rate of decay of the Th-232. After a few years the shorter-lived daughter products will be in equilibrium with the rate of Th-232 decay.

For every Th-232 decay, there will be 6 alpha particles, 4 beta decays, and roughly 4 gammas, if I have counted correctly. There is some variability in the gamma emission, depending on the precise decay path.

Cheers.
--
Alan Robinson

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--
Regards
Roger
http://www.pbase.com/rogerwilmot

alanr0 said:

antoineb said:

like I wrong, the mere potassium (K-40) content in an adult human body, gives about 4'000 radioactive decays per second. And that's just from this source, and then you've got various other internal and external components.

Click to expand...

From the article Dave (Chato) quoted, http://photo.net/large-format-photography-forum/0035DS , the 200 counts per second was for ionisation events detected by a Geiger counter.

You quote 4000 K-40 decays per second from the human body, but only a small fraction of these will be detected by a single hand-held GM tube. From such a diffuse source, little of the emitted radiation will strike the detector. Second, in a the tube is designed to respond to both gamma and beta radiation, the gamma efficiency is usually low, and any beta radiation needs to enter via a thin window, which is usually fairly small. http://en.wikipedia.org/wiki/Geiger-Muller_tube

For typical Geiger-Muller detector I would dispute that "200 counts a second is nothing". In my opinion, "Don't panic, close the lid, and put it back in the cupboard" would be more prudent. Of course, you may simply have a different approach to risk than my own (which in turn seems less cautious than Dave's) ;-).

Cheers.
--
Alan Robinson

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Acceptable risks

I fix boilers for a living. A job more dangerous than being a Cop or a Firemen. I also take risks when I'm out shooting wildlife.

Or as other have pointed out life is a risk, and all of us will die eventually.

But fixing boilers pays the rent, pays for my photography equipment. Taking risks when tracking wildlife is tremendously enjoyable.

But why should I use a radioactive lens, even if the danger of harm is one in a thousand? What benefits do I get from using such a lens, as opposed to another?

Zip, zero, nada. Nothing at all. Now there have been at least a dozen links posted proving that the old Thorium lenses produce a measurable amount of radiation that is potentially harmful. These people can clown around with their bananas, or they can clown around with their newer and far less radio active thorium lenses, but in the the old ones, the glass was 17 percent thorium by wieght.

I really don't need this kind of additional hazard which adds nothing to my life, and yet adds an additional risk...

When I hear of someone who meets the challenge of an unclimable mountain, I may not ever want to do something like that, but it never occurs to me to be critical. They are making a choice. Those who wish to shoot with a radiactive lens, well, I have no respect at all for that choice...

And the manufacturing of such lense is now illegal.

Dave

Richard said:

Gamma is more dangerous but the stuff they use now days is safe. My watch has glow in the dark hands, not problem for me though.

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The radioactive glowing compounds used ionizing radiation to cause the glow. They did not need to be exposed to the light before starting to glow, and the glowing would not stop until the radioactive substance depletes. That same radiation can damage the DNA in your cells and cause cancer.

The first generation used radium, which emits alpha radiation. As you noted alpha particles cannot travel far enough to cause the damage to the skin through the thickness of a watch or even air. The problem with radium is that chemically it is similar to calcium, and the factory workers exposed to radium paints accumulated it in their bones instead of calcium, thereby having direct exposure to radioactivity, and suffered from cancer and other effects.

The next generation used promethium, which is a beta emitter. Beta particles are simply electrons, and are also used in all CRT screens that use electron guns to make the phosphor glow. Promethium's beta particles can cause X-rays when interacting with certain substances, and is therefore a health hazard. It does not replace calcium in the bones, so is safer than radium in that respect, although the radiation is more dangerous.

The third generation used tritium (an isotope of hydrogen), which is also a beta emitter. Its kind of beta particles cannot cause X-rays, can travel only about 1/4 inch in air, and can't penetrate beyond the thin dead skin layer. This is the safest permanently glowing technology.

The modern glow in the dark compounds use an entirely different principle. They have molecules that can be excited to an energized state by the visible light and then due to the laws of quantum mechanics get stuck in such state for a long time. As they after a while come down from this energized state to the ground (lowest energy) one they emit the excess energy as visible light. There is no ionizing radiation involved, so if you don't ingest or inhale such substances they are safe for handling in the longest term. The drawback is that the need to be charged in the light, as there is no internal source of energy for glowing.

Vlad

Roger Wilmot said:

I think we are all agreed on this one. The point I was making was that, for the same activity, the dose from Th-232 is higher than from many radionuclides with shorter half-lives because of the strong gamma emissions from its short-lived daughters. So it is the assertion that "long-lived radionuclides don't give significant doses" that I am contesting.

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Agreed.

In fact the half-life of K-40 is fairly long too, 1.26 10^9 years c.f. 14 10^9 years for Th-232. If we account for the 0.012% natural abundance of K-40, then thorium plus equilibrium daughter products is several hundred times more active than the same weight of potassium.

The activity of typical potassium-rich foods will be tens of thousands times less than a lens containing 20% thorium by weight. Potassium is the largest contributor to naturally-occurring radiation in human tissue and most foods http://www.ead.anl.gov/pub/doc/potassium.pdf .

Cheers.
--
Alan Robinson

Chato said:

But why should I use a radioactive lens, even if the danger of harm is one in a thousand? What benefits do I get from using such a lens, as opposed to another?

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My comments were not a criticism of your approach. Small but finite risk. Zero benefit. The logical course is to avoid. Even if the chromatic dispersion is OK, the AR coatings won't match the performance of good modern lenses.

Chato said:

When I hear of someone who meets the challenge of an unclimable mountain, I may not ever want to do something like that, but it never occurs to me to be critical. They are making a choice. Those who wish to shoot with a radiactive lens, well, I have no respect at all for that choice...

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I am a little more laid back, but I am not at all tempted to acquire any of these lenses. The immediate risk may be low, but I am not sufficiently curious to want to own one. I have my own risk budget, and I am not going to spend it here.

For me, a more practical question is how to dispose of such items safely. I would not toss into the trash for collection, and I suspect our municipal recycling centre is not prepared to handle such materials. How do I make sure it is handled properly in the event I unexpectedly fall under a bus, or off a cliff?

It is irresponsible to claim there is NO risk.

Cheers.
--
Alan Robinson

Hi to all after many years since this debate begun

I just want to add that I have chance to measure gamma radiation with an old gamma meter. The only lens I have from the "radioactive" list is Olympus Zuiko Pen F 1:1.8/38mm, which is indeed not hot in terms of gamma rays, but clearly measurable (e.g. not burried in background radiation).

However, Olmpus OM 35 F/2.8 les in significantly hotter. I measured 0.1 mR/h. I know it adds to confusion that my meterwas officially calibrated in 2003 and not since, hoever, there is no doubt a lot is going on in terms of radiation.

And it's not alpha particles that I measure, since I have gamma monitor and 1 cm of paper between the lens and the detector has no effect. Even measured at the rear side of the camera with lens mounted on (metal shutter and camera body should stop beta particles as well) reduces measurement just because of larger distance from the source.

The 35 mm F/2.8 OM lens isn't listed on the "radioactive" list. Yet.

Sure there are some LF lenses that have some (negligible amount) of radiation. Look, unless you are taking pics 1/2 mile from Chernobyl reactor....you have really no concerns.

I would agree.

godfrog said:

Chato said:

panamamike said:

Just wondering if the radio active lens element could damage a digital camera sensor.

I had always assumed the radio active element was the front most glass. I read somewhere it's the rear element, one closest to the lens.

Anyone have thoughts?

Regards,

Mike

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If there is anything radioactive about my equipment, I'm dumping it, suing the manufacturer, and I'll worry about my health a lot more than I'm going to worry about the sensor.

Dave

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The world is radioactive.

Those lenses are radioactive too, but in order to contribute any significant amount of radiation you'd pretty much have to sleep with the lens inside your pillow for 50 years or so. If you ever find a scary amount of radiation measured from one of these lenses, it is by measuring at the very surface of the lens, unobstructed. That value is relevant only if you remove the lens element and tape it your forehead.

A single flight (or even worse, an x-ray) is going to expose you a lot more radiation than using a Takumar 50/1.4 for a lifetime. Eating the lens might be a bad idea though.

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Lol. Thanks. It’s funny because it’s so true. But also a bit sad, because people get worried by this then go and sink their babies in asbestos filled baby powder. A single flight will get you more radiation that one of these in a lifetime. We should ban and sue all airlines, and probably earth, and why not all visible stars in the sky, plus the Big Bag. Now that’s a lawsuit and a good way to stay safe.

The reason we stopped using these materials is to not have this in land yards or recycled.Same with lead glass. But we couldn’t stop our vanity since essentially that’s Swarovski glass in every necklace and beauty charm.

antoineb said:

As a final note, did you know that YOU ARE RADIOACTIVE? All that potassium in our bodies causes over 4'000 radioactive decays PER SECOND? Much more than any of those supposed dangerous lenses.

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In other news, “Thorium Lenses sue humans for irresponsible human banana consumption”. Myth Busters would have so much fun with these scare crows for lenses.