Manual Lens Canon Rangefinder 35mm f1.5 Wide Angle Lens is Highly Radioactive

M. Valdemar

Top Veteran
New York City
I was testing some of my vintage Rolex dials for radioactivity with a dosimeter.

Out of curiosity, I pulled out some of my rangefinder lenses and tested them. I had one collapsible 50mm Summicron that I was almost positive was radioactive but it was not. So then I tried the 35mm f1.5 Canon and the dosimeter went haywire.

SUPER high radiation.

It's curious, because I never see that lens mentioned as having radioactive elements. I wonder if my is a fluke or maybe it is not just common knowledge.

Can anyone shed any light? A Google search does not reveal much.


Does the lens have a yellow cast? That could indicated a thoriated glass; these become more yelow as time goes by.
I have a Canon 35mm f2.8 that has a ‘nice’ warm cast, so I expected a part of Flint glass in it.
I bleached out the yellow in my hot-glass Summicron and Pentax 50/1.4 using a UV light. Do not use UV-C, it will not penetrate far enough into the glass. The Summicron is uncommon as the front element is Thorium glass. I keep a filter over my two. Summicrons with Sn higher that 105xxxx discontinued use of Thorium.


The only 'hot' lens I own that I know of is this 35mm 1.4 Nikkor.
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