Warning, radioactive lenses!

Struan,

 

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Thanks for the info. I've been wondering what the proper method for

affixing and Aero-Ektar to the cat was.

Just take a look at what is being sold on Ebay. Those

Rodenstock Heligon lenses come out of Xray machines, not

process cameras.

No worries John, just remember that it's kinder to shave the cat

first.

dsdfsfd

Looks as this one has had a fair dose of Roentgen! ;-)

I trade WWII Aero lenses, all from the US Army Corps, 1940's, mainly

Kodak, my favorite that I use with my Calumet is a 12"/5.0 Aero-

Anastigmat, I also have a 12"/2.5 and a 13"/3.5, and a dozen Copying

Ektanons and Copying Anastigmats, they don't glow green in the dark

though, but I'm wondering if the risk is high enough to just toss

them, or if there is no risk at all. I keep them all downstairs in

the basement. Comments?

Folks,

 

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I just saw the thread, so I'm late. I do radiation protection for a

living, and have for about 27 years now. The radiation protection

field is based on the simple principle that no radiation exposure is

acceptable without a corresponding benefit. Here, this means

enjoying the benefits of a good lens.

 

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The radiation levels associated with most lenses are relatively low

compared to other consumer products and activities people perform.

The human body has about 250,000 dpm of radioactivity, mostly from

naturally occurring potassium-40. If you're worried about lenses,

you should never, ever, consider flying since cosmic radiation

levels go up as a function of altitude (10 mrem or so per flight,

avg). Living in Denver for a year will expose you to many, many,

times the yearly dose than being around most lenses. Oh, and get rid

of those smoke detectors. Smoking adds 1-5 rem per year from

radioactive lead which is a decay product of uranium and is

concentrated by the plant. If you smoke, forget about lenses. The

average dose per year is about 360 mrem, from nature in general.

Fiestaware (the old orange stuff) was coated with uranium oxide and

vaseline glass was also colored with uranium. So is dental

porcelain (the uranium makes your dentures match your teeth under

all types of light). Exposures from lenses would be miniscule

compared to the sources above.

 

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Thorium (and other rare earths like lanthanum) generally comes from

monazite sand deposits, so don't worry about lenses if you live in

Rio de Janerio, Kerala India, North Jacksonville Beach, or a large

portion of the southeastern US coastal plains. The White Mountains

in New England also have significant thorium so don't live there

either. The southwestern US has a lot of uranium, so forget living

there too. Not much left, is there?

 

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The US Nuclear Regulatory Commission (and I assume the Brit's

corresponding rulemongers) places restrictions on radiation levels

from consumer products, and it used to be about 3-1/2 mrem per hour

which would very roughly translate to 10,000 dpm with a geiger

counter. The National Committee on Radiation Protection and

Measurements (NCRP) has a publication on radioactive consumer

products which is a nice read if you're interested. You should be

able to find it in most good libraries.

 

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Don't think old lenses are less radioactive. The daughter products

are constantly replenished from the thorium parent, which has a half

life of billions of years. However, if you want some real

perspective, take your geiger counter through an antique shop and

check the glass and glazed ceramics!!

I too am late to this thread, but read its contents with great

interest and amusement. As a radiologist, I am particularly impressed

with the last response which is very informative. In all this

discussion (some of it erudite), it is worth remembering that we bask

in the life giving radiation of an enormous and self-perpetuating

thermonuclear explosion i.e. the sun. As for 'no safe dose of

radiation', without it we would'nt exist in the first place.I really

would'nt worry too much about some old lenses.

I *still* haven't made the measurements on my Aero Ektar, but

Mikael Briggs has some worthwhile information here:

 

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

ml

 

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Mine now lives in the cellar rather than my camera cupboard. My

wife wants me to get rid of it, but where else can I get a lens that

burns bugs so spectacularly?

 

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Incidentally, I read on usenet that at least some of the colour

centers in some of the radioactive lenses can be bleached by

leaving the elements exposed to sunlight. If you are using these

lenses and want to get close to their original performance, this

might be worth a try.

Anyone tried these kind of tests on 35mm lenses? I have an FD 35/2

that's yellow and somwhere I read thorium was used in the glass, the

lens construction is awesome, but I was concerned about the possible

dangers, and if there's any possibility to get the originalk tint

back. thanks

A late addition to an interesting subject. (I'm a Ph.D. radiochemist by the way and the Radiation Safety Officer for our company)

 

With the exception of the thorium glasses, we are talking about VERY LOW fields here. I'm routinely involved in nuclear medicine scans where patients are administered safely and routinely much larger amounts of radioactivity. These scans result in less dose than a chest X-ray to put the safety into perspective.

 

The thorium glasses I hear are on the order of 1.5-2.5 mR/h which are low, but by no means insignificant. Do take care to limit your contact exposure to the lens (time, distance) and I wouldn't store it next to any boxes of film!

 

If you are interested and have money to spend, check out Aware Electronics at http://www.aw-el.com/ These guys can hook you up with a nifty little thin window Geiger Muller counter for $150. You can use it to monitor Radon levels in your basement when you're done with lenses if you rig it up to a PC ;) I've recently designed a radiation safety system based on these little pocket GM tubes and they work very well indeed. I think I'll put one in my pocket next trip to the camera shop ;)

As an illustration, an autoradiogram of some radioactive lens cells that I did recently out of curiosity. I placed the back cells of the three Repro-Clarons I own (355mm, 210mm, 55mm) directly on a TMAX 100 Readyload envelope for 19 days, with the convex element (the hot one) towards the film. Since the lens is symmetric, the front cells would work too, but the mount is deeper and would have increased the distance from lens to film. The film was developed for 14 min in TMAX RS 1+9 at 24°C (75F) (about N+1 1/2 for me).

 

The visible effect is apparently dependent on the focal length, most probably because the lens element volume scales with the focal length, so the 355mm has the strongest effect, the 210 shows less density, and the 55mm does not show a visible effect. Anyway, it is probably not a good idea to keep film and these lenses in close contact for extended periods of time (or carry them in your pocket).<div></div>

Hi all

I just came across this thread and read it with interest.

I was supprised by the number of people here that did not know about this problem.

You will find this has long been known to users of 35mm format Pentax Super-Takumars.

The main culprit in this regard is the early eight element 50mm f1.4 Super Tak, which I used to own myself and has Radioactive Thorium glass elements.

I only had mine for about a week and got rid of it quick so hopefully I did'nt suffer too much damage to my DNA!

Actually radiation was'nt the main reason why I got shot of it quick, the main reason was it was totally useless WO so it could not fufill the purpose I bought for in the first place,..as a fast lens.

The later 7 element 50mm f1.4 Super Tak was apparently able to dispense with the need to use radiactive elements so that particular lens should be ok?

However, trying to tell if its the new or the old model BEFORE you buy one is the hard part!

Anyway I noticed a few users here asked how to cure the yellowing of the Radiactive Thorium glass elements...its actually very easy.

Buy yourself a UV lamp and place it in a housing large enough to hold the bulb and the lens. "Bathe" the lens in UV like this for about 1 week continuously and this should cure the yellowing.

Now I wonder if my Taylor-Hobson 12" f4 is safe?

 

Regards

 

Alf

Um, Alf, I have two (2) of those 12"/4 Taylor Hobson telephotos. Long story. Anyway, AFAIK they don't contain radioactive glass.

 

Taylor Hobson f/9 tessar-type process lenses are something else again. I have three, badged, respectively, Cooke Copying Lens, Taylor Hobson Copying Lens, and Apotal. All three had yellowed rear cells when I received them, all cleared after nearly two months under a 20w BLB fluorescent tube. I wouldn't carry any of them in a pants pocket.

 

Don't worry, be happy,

Oh no, I just bought that very same lens at a thrift store for two dollars. Very interesting and enlightening information.

<p>If this level of radioactivity is disturbing then there is more disturbing fact:<br>

If your weight is 70KG then:<br>

<strong>There are 500 decays per second of Potassium-40 in your body that emits GAMMA RADIATIONS.</strong><br /><br /><strong>There are 3,900 decays per second of Potassium-40 in your body that emits BETA RADIATIONS.</strong><br>

<strong>The Carbon 14 inside your body emits 3,700 Beta radiations per second<br /></strong><br>

Source:<br>

http://www.physics.isu.edu/radinf/natural.htm<br>

http://www.rerowland.com/K40.html</p>