Radioactive glass???

[PasMichiel]

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I saw this article, but my chinese isn't that well:

Radioactive Summicron

[PasMichiel]

Sorry it's Japanese. I tried Google Translate

 

But still never heard about Radioactive glass

[Guido]

I believe this is similar to some old Canon lenses, which contained radioactive Thorium glass in an attempt to increase optical sharpness. This glass turns yellow over time, as can be seen on the photos of the Summicrons.

[lars_bergquist]

Glass with small amounts of thorium was used in the prototypes, and possibly in the very early production of the Collapsible 50mm Summicron, way back in 1951--53. It is also said that, in order to prevent fogging of the film when the lens was collapsed, the rear elements were lead glass, which does in fact often have a faintly yellowish tint. But the Leitz glass lab had already developed thorium-free lanthanum glass when the M Summicron appeared in 1954, and I do not think any lens in M mount was radioactive. I have not heard of anybody exciting a Geiger meter with a screw mount one, either.

 

The old man from the Age of Ludwig Leitz

[jaapv]

The use of Thorium glass was quite widespread in optics before the 1960ies. Telescope lenses, camera lenses, microscope lenses, many contained the element. There have been concerns expressed about the health risks of such optics, especially microscope oculars, but on objective examination those are nonsense. The test to determine if a lens is radioactive would be to lock it away in the dark on a piece of film (preferably x-ray film) for a week. Considering that it -for instance- takes 1/20th of a second to get a dental X-ray, and that the amount of radiation absorbed by the body in that case is equivalent to the amount received when flying from London to Berlin, the radiation emitted is so minimal as to fall below even the strictest threshold.

Now if one was to ground such a lens up and ingest the powder, that might be different, as Thorium does accumulate in the bones.

Just to prevent legend-building - medical X-rays nowadays are digital, cutting radiation by 90%.

[eduardoho]

Thorium oxide and Lanthanum a mildly radioactive coatings were used in the late 50's into 60's as expressed in the previous postings. The Soviets used extensively in their lenses, and Chinese copied them as well. Notably Kodak also used in their lenses too. From what I can read, they are boasting about the radioactive properties of the coatings, may be done locally, relying as the selling point for the lenses. Please understand that certain English words are used loosely with different connotations throughout non-English speaking countries. I do not know whether these lenses were actually coated with thorium or lanthanum compounds.

[SJP]

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transition metals are very intereresting for optics , Ta2O5 has an index of refraction of about 4.5 (normal glass is about 1.54, water 1.33). Similarly TiO2 has very high refractive index.

 

So Thorium (oxide) should be a good candidate for optics & if I recall it is a mild alfa-emitter so it should not pose any problems.

[adan]

To clarify - this was not a "coating" - it was thorium compounds mixed into the glass itself. Glass is primarily silicon dioxide, but other metal/metalloid oxides (boron, lead, thorium, aluminum, magnesium) are usually mixed in to change various properties of the glass, including the optical properties.

 

It might be noted that the most common isotope of Thorium (232) has a half-life of 14 billion years - so it is not exactly spitting out a lot of alpha particles on any given day.

[lars_bergquist]

The radioactivity problem was of course largely psychological. Before WWII it was actually a selling point that something was radioactive -- not least 'health-giving' spa waters. The general public felt that this mysterious emanation must be somehow beneficial, and hordes of quacks and patent medicine sellers battened on them, with results that were sometimes horrible. Hiroshima and Nagasaki changed all that, very quickly. Now radioactivity was bad, and for the first time, measures were actually taken to protect the public. This was the situation in the West, at least. Having an inadvertently radioactive product was definitely bad for the image (marketing, not photographic) and had to be avoided, however innocuous it was in reality.

 

The old man from the Age Before 1945

[luigi bertolotti]

Interesting is that the role of Thorium, and leaded glass to prevent radioactivity effects on film, was explicitily quoted in Leitz filings for the patents on the Summicron :

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For a deep analisys on radioactive glass, see the (Italian) articles from Marco Cavina

at ARTICOLI TECNICI DI ARGOMENTO FOTOGRAFICO by MARCO CAVINA (search "radio" on the main page)

[roydonian]

I have not heard of anybody exciting a Geiger meter with a screw mount one, either.

 

I've seen it done. At a committee meeting of the Leica Historical Society around 2005, someone brought along a Geiger counter. My old (and very yellowed-glass) screw-mount 5cm Summicron produced a vigorous response from this device.

 

Best regards,

 

Doug

[lars_bergquist]

Very interesting. What serial number did that lens have?

 

The old man from the Age of Tom Lehrer

[roydonian]

Very interesting. What serial number did that lens have?

1022691

[lars_bergquist]

1022691

 

Thanks a lot.

The old man from the pre-nuclear age

[ho_co]

... Before WWII it was actually a selling point that something was radioactive ...

 

I was born during WWII.

 

I remember shopping for shoes when I was a kid, and being able to stand, place my feet into a viewer, and look through a glass to see an X-ray view of my feet in the shoes. Live, full motion. Watch yourself wiggle your toes (green bones, as I recall) while supposedly confirming that the shoes fit. Looked rather like the peep-show machines around at the time. The machine wasn't there next time I bought shoes.

 

I attended some fair in Texas, where I put a dime into some device which then irradiated it and packed it in a plastic-and-metal holder with the label "radioactive dime" or some such. Put it happily in my pocket and went on about my business.

 

Takes us a while in the US to pick up on these threads.

[fotofoto]

 

Takes us a while in the US to pick up on these threads.

 

Duck and Cover ;-)

[Tritz]

I just stumbled upon this video demonstrating the radioactivity on the 50mm f/2 Collapsible Summicron, and thought I might share:

 

 

I also found this list of radioactive lenses. Apparently there are quite a lot of them, but only 1 Leica lens:

 

http://camerapedia.wikia.com/wiki/Radioactive_lenses

[M9reno]

Leitz Wetzlar Summicron 5cm f2 (M39) is further down the list. Presumably this is the slightly later rigid version, or a duplicate of the earlier version already on the list?

[peterbengtson]

Brilliant red Fiesta dinner plates were radioactive (I ate off them as a child).

 

http://en.wikipedia.org/wiki/Fiesta_(dinnerware)

[Guest jvansmit]

instead of counting sheep, those who have extreme difficulty falling asleep at night might like to read:

 

http://www.nrc.gov/reading-rm/doc-collections/nuregs/staff/sr1717/nureg-1717.pdf

 

 

from US Nuclear Regulatory Commission's Risk Analysis Division

 

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Hallo,

Look here: Interesting Leica gear