[MarkJerling]

A friend was going to get Granite work surfaces in her new kitchen - until I mentioned that Granite is naturally slightly radioactive, so she got MDF instead. She was actually working in a 100 or so year old building constructed mainly from Granite at the time.

Completely forgetting about all the VOC's in the MDF of course. Love it!

[gaweidert]

What most people do no realize is that we have evolved in a radioactive world. It has always been here and always will. We actually can withstand some level of it without harmful effects. I for one am perfectly normal................................. Really!!!!

[Argos]

My understanding is that the thoriated lenses will emit alpha radiation.
Alpha radiation is not very active, in fact cannot even pass through a sheet of paper.
Only problems that exist are if the lens element is pulverized and the dust/particles are ingested.

Here are my measurements of Takumar lenses. Measurements taken with the lens flush to the measuring device. Picture of measuring device shows background radiation.

[jdd]

Interesting thread here, but I want to add one piece of information -- these lenses were made for film photography. If the radiation emitted had been in anyway harmful the radiation would have caused the film to fog.

Do lense manufacturers normally create products that destroy film before a picture is taken? How long would a product have lasted on the market if, after being mounted on a camera body, the entire roll of film was basically worthless? Do photographers often view the destruction of their primary means of income as "not a big deal"?

People use "film badges" to measure radiation exposure for a reason. So, maybe people never reported this because they were embarrassed that they purchased a lense and every roll of film they attempted to use was destroyed, but I have trouble believing that. I also have trouble believing that people discovered the issue, then only kept a lense on the camera body for a few seconds before taking it off to protect the film from fogging, and then never said anything about it. That everyone who's ever used a lense with thorium has kept this "film fogging" secret to themselves and never spills the info.

If the radiation was a problem, we would have heard about it, and there would be a wiki page and 50,000 different sites talking about all the film that was ruined and the engineering and product fiasco that the lenses were.

Concerning radiation and CCDs, the only way to damage a CCD with radiation is for the particle to be energetic enough to create a plasma tunnel in the substrate. All other "damage" disappears through charge annealing (you either wait for the excess charge to drift out, or you can bake it out. I used to put MOSFETs in my home oven at 450 degrees for 6 - 8 hours to reset them). That charge collection as a particle passes through a substrate is how solid state radiation detectors work. If you put a lense on your camera and all of a sudden every image has weird pixels set that don't match those around them, then you have a radiation problem. If after the first pixel issue you notice the pixel doesn't go back to normal after a few minutes/hours, you have damage. But agin, if these lenses where producing radiation hot enough to create plasma tunnels in a CCD, or even flip pixels in a CCD, they would have been fogging film like crazy. No one needs to go pulling out any Geiger counters.

Just saying.

jon

[Paul the Sunman]

Here are my measurements of Takumar lenses. Measurements taken with the lens flush to the measuring device. Picture of mesuring device shows background radiation.

I am very impressed that you managed to get your hands on so many Taks!

[Argos]

I am very impressed that you managed to get your hands on so many Taks!

As the author of two books on Pentax M37/M42 cameras and Takumar lenses, I felt obliged to do some research.

[photogem]

...... No one needs to go pulling out any Geiger counters.

Just saying.

jon

You information is appreciated, but .... particular with a first post in this forum "sans introduction", I found this last commentary of yours kind of rude; particular as Gerjan just offered his measurements and made that effort to present them.


Usually in this forum one brings first an intro about who one is, which equipment etc.

To "barge in" like this ... well...

[photogem]

@MarkJerling once answered with this post which I found very useful:
Which lenses are radioactive and are they dangerous? - Page 4 - PentaxForums.com

I have attached a Swedish analysis which sheds some "not-radioactive" light onto the matter.
It is the same one Mark mentioned in his post but when I clicked on that link I got a warning message,
but as I have it on my pc I thought I upload it here.

[MarkJerling]

Thanks Heinrich, I've forgotten about that study!

[ZombieArmy]

They are incredibly dangerous and must be disposed of immediately. I will send my address to anyone who needs radioactive lens disposal.

[Digitalis]

I will send my address to anyone who needs radioactive lens disposal.

Be careful what you ask for someone might send you a few old large format Aero Ektars*, which I wouldn't touch with a 6 foot tungsten pole.



* It is said they are so viciously radioactive if they are carelessly left to rest upon a box of Polaroids they will severely fog the entire box in a matter of minutes.

[gaweidert]

Here are my measurements of Takumar lenses. Measurements taken with the lens flush to the measuring device. Picture of measuring device shows background radiation.

The only time that the film would be exposed to any radiation would be during exposure. X-ray film has very large silver halide crystals. Larger crystals mean more sensitive film. Back in the 1980's. 25% of the weight of a sheet of x-ray film was silver.


According to the Gurney-Mott theory of latent image formations, it takes three photons to strike a silver halide crystal in order for it to be reduced quickly by a film developer. A larger crystal has a greater chance of being hit. X-ray film has very low resolution as a result of the larger crystals.


Photographic films do have additives that can increase sensitivity. Gold chloride being the main one that I know of.


As measured with my GQ GMC-600+ Geiger Counter I get the following measurements.

At lens surface:
16,900 CPM (Counts Per Minute)
49.9 uSV/Hr.
5.35 mR/hour.


At the front of the lens I get 300 CPM.

At the film plane with the mirror down and the shutter closed I get around 600CPM.

125mm above the rear of the lens (The rear element is the radioactive one) radiation is already dropped to 10% of what it is at the surface of the lens.


My current background radiation level is fluctuating between 25 and 44 CPM.


The low level of radiation reaching the film may theoretically increase sensitivity a tiny bit.


Why was thorium used? It was used because when added to the formulation the result is exceptionally clear glass capable of razor sharp images if ground correctly. The yellowing was only discovered years later. I have seen glass from high altitude aerial recon cameras that has turned very yellow 30 years after it was manufactured. Quite pretty.

If you have any old hurricane lamps in your house, that nice cloudy glass they now have is the result of uranium oxide in the glass. Under ultraviolet light they glow quite a pretty green. Uranium glass started appearing in the 1830's. Even drinking glasses and tableware were made from it. never had a chance to measure how much radiation comes form the stuff.

[ZombieArmy]

Be careful what you ask for someone might send you a few old large format Aero Ektars*, which I wouldn't touch with a 6 foot tungsten pole.



* It is said they are so viciously radioactive if they are carelessly left to rest upon a box of Polaroids they will severely fog the entire box in a matter of minutes.

I'll just wear a lead apron

[Toni60]

Dear all,

I appreciated your replies very informative, wow. I decided to stop using it for the time being because I found that a test was run on Pentacon with non-yellow lenses and they found emissions:
https://github.com/norayr/radioactive_lenses
I need to read all of your information and I am extremely grateful for that.
Have a nice day.
Toni

[photogem]

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