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Radioactive camera lenses

 

Radioactive Camera Lenses from the recent past

Radioactive Camera Lenses. 
This article refers to the use of vintage radioactive lenses only.
These lenses were produced approximately between 1940 up to the 1970’s .
WARNING never hold one of these lenses up directly to your eye. (see article)

Modern lenses are not radioactive, but some vintage lenses are.

The digital photographers of today are taking a new interest in using vintage lenses fitted with modern adapters. This page details information all photographers should be made aware of.

Some of the old camera lenses made from the 1940s to the 1970’s contained up to 17% radioactive thorium 232.  Many of these old lenses are still highly regarded today, due to their optical excellence.

Vintage radioactive camera lenses containing thorium have been made by various camera manufacturers; such as Kodak; and many of the other “big name” camera/lens manufacturers.

This article refers to ordinary vintage full frame lenses purchased by normal ordinary amateur photographers from high street shops in the past.
(i.e. This article refers to 35mm lenses, and not just to Kodak Ektars, or medium format lenses).

Frequently the radioactive vintage lenses are the ones made from “special glass” which was used in expensive lenses.
This is not always the case. 
Radiation has been found in old  Kodak Instamatic lenses (usually Ektar lenses ? ).

I  once thought about buying a vintage Kodak “Aero Ektar” lens for my digital photography teaching.
The Kodak Aero Ektar is a highly respected vintage lens, that was originally designed for aerial reconnaissance.

But then I read this page by professional gamma-ray astrophysicist Michael S, Briggs.

I’m definitely not buying an Aero Ektar now.

Thousands of classic vintage radioactive camera lenses are still used today by digital photographers, film photographers, and collectors.  Many of these photographers don’t know about the radioactivity issue.

Photo of  Vintage Thoriated Asahi Pentax Super Takumar 55mm lens showing characteristic yellowing / browning caused by Thorium radiation (you may need to view the lens at an angle to see this colour – don’t confuse browning with lens coatings or aged lens balsam)

Thorinated Pentax Super Takumar radioactive lens (Bill Bagshaw/M. Williams)

Of course the thorium didn’t get there by accident.   It was put there deliberately to make these lenses perform optimally.   This was at a time when the radiation risks to assembly workers were not fully understood.

http://camerapedia.wikia.com/wiki/Radioactive_lenses   is a list of some camera lenses which they believe to be radioactive  (authors opinions on radioactivity effects are not necessarily ours )

Are these vintage radioactive camera lenses dangerous ?    (Opinions differ)
Some would say no, (apart from holding them up to your eye) since thorium 232 emits Alpha particles which can be stopped  by thin layers of skin, but not by your eyes.
However thorium 232 also decays to “daughter particles” which emit beta radiation, and apparently also gamma radiation.
Some would say the beta radiation isn’t that dangerous compared to other radiation sources in our environment.
Others say the beta and gamma radiation is dangerous, and that these lenses should be treated like nuclear waste.
Other people say the radiation risk is minimal, and that smoke detectors are far more radioactive.

Authoritative sources state that Thorium 232 decays to emit penetrating gamma radiation, as well as alpha and beta radiation.
Others say the radiation from these lenses is nothing compared to what you get from a granite worktop.

Personally I see no reason why I would want to increase my family’s exposure to radiation by owning one.

Decide for yourself from these external links, and your own research – Make your own mind up, I am not a radiation expert.
Michael S.Briggs’s page
UK government article about safe use of military thorium lenses
U.S. government page about alpha, beta, and gamma radiation
US government link about Thorium 232 decay
Click here to see what wikipedia says. 
http://hps.org/publicinformation/ate/q11530.html

I  noticed that some youtube geiger counter lens test links (further down this page) show people wearing thick gloves.

So what is definitely dangerous about vintage thorium lenses ?
Holding thorium lenses directly to the eye or using them as eyepieces is definitely dangerous.
Inhalation of thorium particles from a damaged vintage thorium lens is very dangerous.
Storing them under your bed (or on the adjacent wall of the room next door), will vastly increase your exposure time.
Carrying them around regularly in a pocket next to your genitals would not be a good idea.
Unknown ( ? ) consequences of  “daughter particles” ? (Michel S. Briggs states that when you store an Aero-Ektar,  the gamma-rays emitted will penetrate some walls and floors).

Now here’s the surprising bit:-
That old thoriated lens in grandads cupboard is getting more radioactive as it ages.
When these lenses were new they contained thorium 232 which was relatively pure. But as the lenses got older the Thorium decayed to produce “daughter products” which include beta radiation, plus gamma radiation.

This is exactly the opposite of what you might think.
Normally radioactive substances become less potent over time.
But in this case the thorium is decaying to produce more dangerous types of radiation; in addition to the alpha radiation.
Check out this Health Physics Society public information link about the decay of thorium 232

The half life of Thorium 232 is 14 billion years.

How to identify a vintage Thoriated lens:-
Thorium lenses can often be identified by a Yellow/Brown discoloration of the lens.
This colour can be difficult to see; and can be best observed by reflecting a white reflector into, or behind, the lens.
NEVER hold a suspect lens up to your eye.  This is because your thin eye membrane allows penetrating radiation to be absorbed.
However some non-thorium vintage lenses look yellowed anyway; due to either ageing of the balsam or due to anti reflective coatings.
Additionally exposure to UV  light can eradicate the yellowed look of Thorium lenses.

i.e. The best way to test if your vintage lens is radioactive may be with a geiger counter.  But geiger counters can vary as to what type of radiation they detect. Some are not as accurate as others.

Here are some You Tube amateur geiger counter tests of vintage full frame prime lenses, etc.
We cannot vouch for their accuracy, so bear that in mind.
We cannot of course vouch for any of the safety and handling procedures in these videos.
(i.e. We have no idea how accurate or inaccurate they are, and no connection with them whatsoever) 

I  noticed that some youtube links show people wearing thick gloves.

SMC Takumar 55mm f1.8 lens  geiger test on You Tube
Super Takumar 55mm f1.8 lens geiger test on You Tube 
FD 55mm f1.2 lens geiger counter test on You Tube
Fujinon 50mm f1.4 (early type pre EBC) geiger counter test on You Tube
FL 50mm f1.8  geiger counter test on You Tube
OM 50mm f1.4  geiger counter test on You tube
Summicron 50mm f2 collapsible M39  geiger test on You Tube
Hexanon 57mm f1.2  geiger test on You Tube
Yashinon 50mm f 1.4 geiger counter test on You Tube
Super Takumar 50mm f1.4 geiger test on You tube
Kodak Fluro-Ektar 111mm f/1.5 geiger test on You tube

By comparison heres an amateur You tube video of a an ionisation (Americanium) smoke detector geiger counter reading

Here’s another surprise
Some of these vintage radioactive camera lenses are still renowned (and prized) for their superb image quality.
Thorium glass was a terrific way of improving the optical performance of the lens.
Thorium lenses can be highly sought after and hence expensive.

Footnotes
The use of radioactive materials in lens manufacture is now banned.
Opinions differ as to whether these lenses are dangerous or not.
There are still plenty of secondhand vintage thorium lenses on the market today.
Vintage fast (more expensive) lenses are the most likely to contain thorium. – The very same type of  lenses that are prized by enthusiasts and collectors.
Some thorium lenses may have been described as “rare earth” lenses when they were new.
Lens manufacturers changed the content of their lenses from time to time.  Just because someone else’s lens matching the description of your lens is thorium free doesn’t mean your lens is thorium free.
Browning/yellowing can be a useful indication of thorium content.   But your thorium lens may have been deliberately de-browned by a previous owner who exposed it to UV light

Bottomline
Do I personally want to expose members of my family (including children) to the proven risk of holding one of these old lenses up to their eye ? No.
Do I personally want to expose my family to potential risks that others argue about  ?  No
Are there lots of great alternatives to owning an old thoriated lenses ?  Yes

 

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