Thoriated lenses for MF Mamiya cameras (RB/RZ67, C330)?

"* Unless it is a bananaphone," LOL.

Was in a camera store several months back and a nuclear engineer (local professor) brought in a geiger counter and started checking lenses. The most radioactive lens in the shop was a 55mm for an RB67. Several old Pentax Tacomar lenses were also radioactive, but not off the charts like the 55.

Eugen Mezei said:

What is the problem with brick buildings? Never heard of bricks being radioactive.

Click to expand...

Read this:
https://doris.bfs.de/jspui/bitstream/urn:nbn:de:0221-201210099810/3/BfS_2012_SW_14_12.pdf

"Due to their geological origin, all raw materials used in the manufacture of building materials contain a certain amount of natural radioactivity, especially from Potassium-40 and the radionuclides of Uranium-238 and the Thorium-232 decay series. These radionuclides cause during the stay in buildings a radiation exposure of humans."


But of course if you stay in a brick building with a thoriated lens and a Geiger-counter, the counting effect with and without such lens near the meter can be frightening.
I should add that just the lens itself can have a barrier effect, depending where the respective lens element is located. So you might read a max. value at one end and a min. value at the other, even down to room level.


Measurement of radioactivity is a tricky thing, so take any DIY metering with a grain of salt.

None of the RZ lenses have thorium or lanthanum glass.

EdSawyer said:

None of the RZ lenses have thorium or lanthanum glass.

Click to expand...

Thorium was phased out, but Lanthanum is still a current optical additive.

Thorium was phased out as an optical glass additive before the RZ line of lenses was introduced. But there is no reason they would not use Lanthanum, as it is a current, non-radioactive, non-toxic glass additive that is very useful.

M. Axel Wikstrom said:

Several old Pentax Tacomar lenses

Click to expand...

Mmmm, Tacomars are yummy!