I read this article in Petapixel about old radioactive lenses and I realized I have one of them!! So I gave it a try with a portable geiger counter I bought in Japan a couple of years ago.
I’m not an expert on the matter, anyway the normal safe level is 0.05μSv/h and the lens was 5.00μSv/h It’s not dangerous, but it was cool to see that indeed they made these lenses with some radioactive elements.
Based on this question posted on the website of the Health Physics Society, the element used was thorium to increase the index of refraction of the lenses. Based on the answer the use is safe and in their own words:
…the dose rate near the viewfinder of an old Pentax camera of mine (Super Takumar lens) is roughly 100 microrad per hour—approximately ten times background. In other words, looking through the viewfinder of this camera for one minute results in the same dose that I receive every ten minutes when not using it. I would have to hold this camera up to my eye for several million hours to exceed the threshold dose for cataracts…
I’m happy with this lens, in fact the optics of Takumar lenses is great! I use it with an adapter for Nikon to shot video and they work great.
Remember that the world is radioactive and it’s natural to live in a radioactive environment, as far as we don’t surpass certain limits. Anyway if you have a Takumar lens or any other old lenses that you feel afraid to use due their radioactive nature, please send them to me I will be more than happy to keep them safe :)
Check the video bellow to see it in action: