[LargeFormat] Van Ripper didn,t know

[Michael Briggs]

On 28-Feb-2004 Richard Knoppow wrote:
> 

>   I suggest contacting someone at George Eastman House and
> also Rochester Institute of Technology. By memory, GEH had
> to dispose of a number of lenses in its collection because
> they were radioactive.

I doubt that photography curators will be knowledgable about the physics and
biology have high-energy radiation. The area of expertise is Health Physics or
Radiation Safety.

>   Some of the first rare-earth glasses contained some
> Thorium because it gave glass with advantageous properties.
> It is sometimes stated that the Thorium was an untentional
> impurity in Lanthanum glass, but it was a delibrate
> addition. I don't have the patent numbers for the Bureau of
> Standards glass although I have the patents somewhere. The
> formulas for several glasses are in the patent and show the
> use of Throrium to obtain high index, low dispersion glass.
> The patent is not in Kingslake, I'm not sure where I
> orginially found it.

The patent number for the Aero-Ektar is in Kingslake's A History of the
Photographyic Lens: Aklin, US 2,343,627.  His discussions on the new glasses of
Morey and Kodak is a bit misleading in that he calls them Lanthanum Crowns and
doesn't mention that all of these glasses also contained thorium, though he
does mention this fact in the Nature article that he references, Kingslake and
DePaolis, Nature, vol. 163, pp. 412-413, 1949.

You probably got the glass patents from me.  They are Morey, US Reissue 21,175
and Eberlin and De Paolis, US 2,241,249.

It would be very interesting to find the patents (if they exist) for other
lenses using thorium glass, e.g., some Xenotars, a screwmount 50 mm f1.4
Pentax Super-Takumar, the pre-AI Nikkor 35 mm f1.4, Repro-Claron, .....

--Michael