Sankyo Kohki Komura

Goethe wrote:

iTrax wrote:

lot of old lenses , like Pentax Takumar's , will turn yellow with age , I have many of them,

they will not harm you.

You can remove the tint with UV light.

https://www.youtube.com/watch?v=xjGjgqZjzPM

Thanks. I am familiar with radiation in old lenses, from thorium and lanthanum. I'm not worried about any radiation harming me. Well, other than accumulated doses over time. But radiation has the possibility of harming electronics, up to and including dead pixels in the sensor. Not a given, but it can happen. Which is why I asked if these particular lenses might have thorium, because some appear yellow.

If I remember correctly some Takumars emit far more from the front of the lens. But many old lenses emit heavily to the rear.

They certainly **might** be -- but the glass additives that happened to be mildly radioactive also tended to be not too cheap, so 2nd-teir brands didn't use them much.

Short of testing them with a counter, yellowing that clears with UV exposure would be a good hint that they're radioactive.

BTW, I don't leave known radioactive lenses on cameras for storage, but I think the probability of causing structural damage to the sensor (as opposed to a "soft error" within an exposure) is near zero.