Super Takumar radioactivity

[Akira]

Bill, thanks for sharing your insight and the link.  It is surprising to know that there have been much more lenses than I had known that used radioactive glasses (even in the very recent Mitakon lenses, although the half-life period of lanthanum isotope is very short)...

[benveniste]

Hello!!
I have been offered a Super Takumar 55/1.8 from a estate distribution. However, I have read these and other older lenses contains thorium and therefore are radioactive. On the internet some people have measured and confirmed it´s radioactivity. My question is: is this a real threat to the health, or is it nothing to care about. As I understand it these Super Tukamars have some nice characteristics, so I would like to try it, but not if they should be avoided due to the radioactivity. Anybody who really knows something about this?

You can read what the U.K. says about health concerns here:
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/383654/JSP392_Lft_29_Thorium.pdf

And from Oak Ridge Associated Universities (A consortium funded by the DOE):
https://www.orau.org/ptp/collection/consumer%20products/cameralens.htm

I wouldn't suggest using one as a loupe, for example.  Nor would I suggest travelling internationally with one.  Some countries such as Turkey prohibit them outright, others require testing and licensing.

[Humboldt]

You can read what the U.K. says about health concerns here:
https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/383654/JSP392_Lft_29_Thorium.pdf

And from Oak Ridge Associated Universities (A consortium funded by the DOE):
https://www.orau.org/ptp/collection/consumer%20products/cameralens.htm

I wouldn't suggest using one as a loupe, for example.  Nor would I suggest travelling internationally with one.  Some countries such as Turkey prohibit them outright, others require testing and licensing.

Apparently there is a difference between homogenous thorium oxide lenses and thorium fluoride coated lenses. The later are "prone to flaking leading to
contamination which could potentially be taken into the body". Question is. How do I know if it is coated or homogenous.

I have tried the lens now. The lens don´t need any UV treatment. The pictures are quite nice.

[benveniste]

The main use of Thorium Fluoride coatings is when UV or IR transparency is required.  (Most BBAR coatings block quite a bit of UV).  ThF4 coatings are also fairly soft.  So while I'm not 100% certain, I think that use of Thorium Oxide was far more likely.