Bill:
I've never heard of a radioactive coating, either. But, in the 60's Leica and,
I think, Zeiss, as well as Pentax (among others) doped their glass with various
"rare earth" materials, notably Lanthanum and Thorium, to increase the index of
refraction of the glass, thus making better lens designs possible. While
lanthanum is inert, Thorium is weakly radioactive. As Aram pointed out, it is
primarily a source of Alpha Rays, which can be stopped by a couple sheets of
paper. You'd get less radiation from a Thorium lens, in a day, than from the
sky.
The radium paint on watch dials was another story.
This bit about emitting Alpha rays makes me wonder if the lens in the Video
that Xavier showed was somehow "doctored".
No matter. Don't worry about radiation from your lenses. Very few have the
problem, and even if some you own do, you'll live to be 110, and still die of
something other than the radiation from your lenses!
David.
Xavier,------
I've never heard of radioactive lens coatings and I don't think I would
ever want a radioactive lens.
I remember numbers that glowed in the dark on watches and clocks many
year ago. They used a radium paint, which was banned in the U.S. some
years ago as too dangerous.
Many of the ladies
who painted the radium paint on the dials suffered mouth cancers because
they wet the tips of the brushes they used on their tongues.
Thanks for the warning.
Best regards,
Bill
On Dec 30, 2018, at 7:55 AM, Bille Xavier F. <hot_billexf@xxxxxxxxxxx>
wrote:
good Day Flexers.
We sometimes remember the good ol' time.
Well, by today standard, it may show we had less expectation.
Here; the effect of an old Takumar lens with a radioactive coating on
a quartz Watch:
https://youtu.be/VQJouNzC_7k
Now what happens to a sensor a digital camera if such a lens is
mounted? hmmmm
Just out of interest. Enjoy...
#-----------------------------------
From : Xavier F. BILLE
mail : hot_billexf@xxxxxxxxxxx
Maisons Alfort - France
