Rob-F
Likes Leicas
It's doubtful I can contribute much to this erudite discussion, as much of it is over my head already. I did work for an AEC contractor in Nevada in a former life, though-- over 40 years ago. I don't remember much, but I recall that Beta radiation is particles, and they can only travel a maximum of 2 and a half inches from their source. Also, they are stopped by any material placed in their way.
Since this thread is in reference to the M8, am I correct in presuming we are talking about the collapsible Summicron? This next observation is something I learned on the internet, so approach it with caution: I understand that the radioactive element in the Summicron is not the rear element, but the one before it; and the rear element is a leaded glass; and that this was done to reduce the radiation reaching the film (or the sensor, in today's terms). And the Beta from the radioactive element would be completely blocked by the rear element. None of this would set aside any concerns, I don't suppose, about the X-ray radiation (which I only just learned about from reading the above).
I can tell you this: I have two collapsible Summicrons, one in bayonet mount, the other in screw mount. If I place them on my light table, I can see the slight yellow color. But I can shoot Velvia, and the color rendition in the slides is acceptable and agreeable. I suppose the degree of yellowing is about like an 81A warming filter--in that while it's there, and it's real, it is quite mild, and within a range often used for balancing color. Hmm, I ought to compare my Crons to my warming filters--might be interesting.
Since this thread is in reference to the M8, am I correct in presuming we are talking about the collapsible Summicron? This next observation is something I learned on the internet, so approach it with caution: I understand that the radioactive element in the Summicron is not the rear element, but the one before it; and the rear element is a leaded glass; and that this was done to reduce the radiation reaching the film (or the sensor, in today's terms). And the Beta from the radioactive element would be completely blocked by the rear element. None of this would set aside any concerns, I don't suppose, about the X-ray radiation (which I only just learned about from reading the above).
I can tell you this: I have two collapsible Summicrons, one in bayonet mount, the other in screw mount. If I place them on my light table, I can see the slight yellow color. But I can shoot Velvia, and the color rendition in the slides is acceptable and agreeable. I suppose the degree of yellowing is about like an 81A warming filter--in that while it's there, and it's real, it is quite mild, and within a range often used for balancing color. Hmm, I ought to compare my Crons to my warming filters--might be interesting.
mark-b
Well-known
Yes, Rob, the Summi-col, Super-Takumar, and the Industar 61 L/D are just a few Lanthanum/Thorium glass lenses we are referring to. In my opinion, the darker coloration in aged glass such as these closely approximates a yellow filter when b&w film is being used.
rxmd
May contain traces of nut
In fact the I-61LD isn't. It contains lanthanum, but not thorium. They're different elements. Thorium is (slightly) radioactive, lanthanum isn't. (*)
It's like saying that because mercury batteries are poisonous, it's dangerous to use iron nails. After all they're made of metal, too.
(*) Actually there's a radioactive lanthanum isotope that makes up 1/1000 of the lanthanum occuring in nature. Its half-life is about a hundred billion years, or somewhere abot seven times the age of the Universe, so for all practical purposes it's not radioactive at all. It's like not swimming in Florida because someone threw a mercury battery into the Atlantic in South Africa.
johnastovall
Light Hunter - RIP 2010
If you have granite counter tops you are getting more radiation from them than a lens. Yes, granite is radioactive. If you stand in the center of the Texas capital building (built of red granite) you will be exposed to higher than background count radiation. In fact some types of granite's radiation is high enough to be considered low level nuclear waste.
Much ado about nothing.
Much ado about nothing.