Warning: This video contains a bit of strong language and disturbing (comical) gore.

Vintage lens lover and YouTuber Mathieu Stern gets a lot of questions about radioactive lenses—will they give me cancer? are they dangerous? should I avoid buying them? These old lenses use radioactive thorium oxide, and this fact gives a lot of photographers pause when they're thinking of buying one... but should it?

In his latest video, Stern pokes a little bit of fun at this fear, doing his very own 'experiment' to see if keeping one of these lenses on his person for seven straight days would cause issues. He also exposes it to a lichen known as usnea barbata (AKA Old Man's Beard) which absorbs radioactivity (no, really).

The results are comically extreme:

Once he's done messing with us, Stern dives into the numbers to explain why radioactive lenses are actually nothing to worry about.

A radioactive lens that contains thorium will give off approximately 0.01 millirem (mrem) per hour. By comparison, a chest X-Ray gives you 1,000x that dose in a single shot (about 10 mrem). That means it would take you 167 days of using the lens for 6 hours per day before you've exposed yourself to a single X-Ray's worth of radiation.

If that's not comforting enough, consider this: according to the Nuclear Regulatory Commission, you receive about 310 mrem of radiation per year from natural background radiation. Just living on Earth is more 'dangerous' than these lenses.

Long story short: you have absolutely nothing to worry about.