Radioactive lens ?!

[gnashings]

Someone please educate me... what is this all about:

http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&category=48552&item=7523328188&rd=1

its apparently radioactive...

Peter.

 

[Ole]

In the 60s and 70s, there were quite a few lenses made which had one or more lens elements containing radioactive glass. In some cases it might have been due to Thorium-contaminated Lanthanum glass, in a few cases it was deliberate usage of Thorium glass.

Some of those lenses have attained "legendary" status, as the optical performance was miles ahead of anything else available at the time. So after 40 years those lenses are still legendary - and still radioactive.

SInce then the use of Lanthanum glasses has become a lot more common, but the refining technique has progressed to the point where the lenses are no longer radioactive. There is good reason to believe that most high-performance lenses made today contain one or more Lanthanum-glass elements, but they are not emphasised to the same degree due to the unfortunate association with radioactivity in the minds of many photographers (and lens reviewers).

 

[Dan Fromm]

http://home.earthlink.net/~michaelbriggs/aeroektar/aeroektar.html

 

[titrisol]

"radiactive" lenses containe less radiation than your home smoke detector system and probably than your watch.

Is just a legend given by the use of rare-earth in the fabrication of glass. Those lenses are probably the best ever made

 

[Claire Senft]

Where can I buy 35mm Xray film?

 

[jjstafford]

You can get approximately 35mm sized 'sheet' film from dental suppliers. It is called 'periapical' film. However, it is very low resolution and regular film is sensitive enough to xrays to suffice.

 

[Ole]

"radiactive" lenses containe less radiation than your home smoke detector system

No.

and probably than your watch.

Certainly not - unless your watch was made no later than 1930.

Is just a legend given by the use of rare-earth in the fabrication of glass.

No - the radioactivity is real. Some lenses are more radioactive than others.

Those lenses are probably the best ever made

No - newer lenses with similar but "cleaner" glass are better. QV the Cosina-Voigtländer APO-Lanthar 90mm - blows the competition right away, including the 1970's APO-Lanthar.

 

[jjstafford]

[...] There is good reason to believe that most high-performance lenses made today contain one or more Lanthanum-glass elements, but they are not emphasised to the same degree due to the unfortunate association with radioactivity in the minds of many photographers (and lens reviewers).

Supposedly Zeiss changed the compound formula for the 38mm Biogon in order to comply with new strident pollution control regulations. Do you know if that has anything to do with Lanthanum-glass?

 

[Ole]

I have no idea what changes were made to the Biogon, nor what glasses are and were used in it. There were a great many different additives used in glass, and there are a great many still in use. If anyone is particularly interested, I have heard that the Schott glass catalogue is an amazing source of information!
I used the APO-Lanthar as an example because I know that my old 150mm is radioactive (checked with Geiger counter), and that the new 90mm's are not. I also know that the optical formula has been changed a little bit, so that the new ones are even better.

 

[Donald Qualls]

That might just as easily stem from lead- or barium-doped optical glasses that have been around for, in some cases, centuries. There's a lot more lead glass used in optics than lanthanum glass -- IIRC, the crown glass in a common achromat (as in a doublet loupe or telescope objective) is often leaded. And the glass "mud" from grinding and polishing lead glass is an environmental hazard on the same order as arsenic bearing mine tailings or smelter slag (though of much less volume). I've heard Germany now requires mandatory recycling of glass TV and computer display tubes, as well, with the recycling costs included in initial purchase price (the sane way to do this, IMO), but the result is that the up-front cost increase is partly driving the runaway switch to LCD monitors (which are inferior to CRTs in some significant ways, even though they are light, compact, and use a lot less power -- most notably, with their fixed size display elements, they don't handle multi-resolution display usage at all well in my experience).

Bottom line, lead glass is on the way out, at least in Germany -- and optics isn't the only industry affected.

Lanthanum glass is likely much less affected, since there's a lot less lanthanum in a given glass than there would be of lead in a corresponding crown, and the higher index and lower dispersion of lanthanum glass allow using less or no lead glass in other parts of the lens.

 

[titrisol]

I'll take your word and expertise for it. My point is that the radiation levels are very samll and are not dangerous for humans or film.

I have at least one of the "radiactive" lenses and I'm very happy with its performance, given it ii a 40 year old lens

One of the things I have noticed is the use of the "Radioactive" term, whether it is true or not to raise the price at the auctions, given the "legendary status" you mentioned.

Newer lenses with similar but "cleaner" glass are better. QV the Cosina-Voigtländer APO-Lanthar 90mm - blows the competition right away, including the 1970's APO-Lanthar.

 

[Ole]

I have at least one of the "radiactive" lenses and I'm very happy with its performance, given it ii a 40 year old lens

So have I, and I'm not selling it!!!

The radiation levels are low, but I wouldn't put it under my pillow. The chance of getting unhealty doses by normal use are practically zero, but if you were to eat it (or sleep with it under your pillow) it's a different matter.

I have also noticed that use of "radioactive", and sometimes worry if we're heading back towards the "Radium Health Spa" craze...

 

[Claire Senft]

JJS Thank you for the information. My posting was meant as a tongue in cheek comment regarding a radioactive lens.

 

[Dan Fromm]

Supposedly Zeiss changed the compound formula for the 38mm Biogon in order to comply with new strident pollution control regulations. Do you know if that has anything to do with Lanthanum-glass?

They got the lead out.

 

[gareth harper]

Certainly not - unless your watch was made no later than 1930.

Not so. I've got a watch made in the 70's, it’s one of those self-winders with a luminous dial. It's the luminous dial that gives off radiation.
Many if not most of the workers in the UK who assembled instrumentation on ww2 fighters and bombers (a luminous paint was used on the dials) got throat cancer. They used to find it helpful to lick the brush now and again I believe. I'd imagine the pilots got a fair old dose considering the number of dials and how crude the luminous paint was, but that was the least of their worries!

A few years ago one of the mechanics at work (I work in a nuclear power station) set of the personnel monitor on leaving the nuclear island. It turned out he had his good watch on that day by mistake, it was an Adidas model (I think)with a luminous dial. It was a modern watch anyway. Strictly speaking it should have been declared a source and not allowed off site. As the contamination was 'fixed' he was allowed to take it home. He was also advised to contact the manufacturer for a replacement or refund, as while it was a weak source it was clearly not a good idea to strap it to one's wrist for days on end.

Like wise that smoke alarm. Stick it in your pocket and given some time it will have a detrimental effect on your health. However screw it to the ceiling and it's perfectly safe. As we say at work, double your distance, quarter the dose.

Oh I still have my old watch, but I certainly don't wear it anymore.
As for radioactive lenses. I'd expect the radiation to be much lower than that of luminous watches and fire alarms etc, but I'm only taking a guess.

Your local school, college, university, hospital or nuclear power staion should be able to check and advise.

 

[BruceN]

OT - Radioactive marbles

I've got a couple of marbles made from this type of glass. They actually glow in the dark, albeit weakly.

 

[gnashings]

Wow, fascinating stuff - the lens looks pretty modern... being an FD mount Canon, it can't date back morethan what - early-mid 70's?
The convex element is also something I have not seen before, but seems to make logical sense when you think about it...
Again, fascinating!

Now, I don't know if this is an urban legend or not, but there is a story in my family about a family member who worked as forced labour in a German instrument factory. She took ill and died, eventually, and the family was allowed to claim the body. In those days, the visitation was usually held in the persons home, the body lying "in state" usually in the biggest room of the house... All was well until during the night, the wind blew out the candles... The mourners were all of a sudden faced with a very..."luminescent" relative...

I have no idea how true that story is, but its a part of the family "folklore" if you will - I know the person was real, and that she died during the war, and was in fact taken to Germany as a forced albourer. That much is documented...the rest is very much word of mouth. The story goes on to include a lead coffin...and I guess it could be easily verified, but no one saw it as important enough to disturb the rest of the deceased (and most likely, rightfully so).

 

[srs5694]

FWIW, I once ran across a page about radioactive FEDs. (The FED was a brand of Soviet, and post-Soviet Ukrainian, rangefinder camera. It was originally a Leica clone, but evolved independently over the years.) It's basically the same story described in this thread, but the page has some quantitative measurements of the radioactivity of the FED's lens, measured in a high school science lab. The level was about 40% of background radiation (so total dose was 140% of background). This was measured, if I read correctly, in direct contact with the lens's front element.

I don't know if the numbers would be similar for the Canon lens in the referenced eBay auction, of course.

 

[Donald Qualls]

Well, here's the thing to remember: "background" varies from place to place. I used to live in Seattle, where the background was very low -- most of the local ground was glacially deposited mud and gravel, which itself was originally sedimentary in origin; the ground there is just less "hot" than some places. Now, I live in North Carolina, where I understand one of the reasons most houses don't have basements is that radon buildup is a real problem -- there's enough thorium in the bedrock and overlying clay to significantly raise the background here.

I'd bet I'm getting more "extra" radiation above the low background I've lived in for the past 20+ years from the soil than from the radioactive element in Super Takumar 1.4/50 -- and I can't put the ground in another room or get further away from it to attenuate the radiation.

In any case, 40% above average background is really, *really* not a big deal. You don't see a huge increase in cancers in the thorium belt on the eastern slopes of the Appalachians, where the background itself is 2-3 times what it is in Seattle (except where basements concentrate the radon exuded from the ground), after norming out lifestyle differences. Smoking is MUCH more dangerous, even than basements full of radon...