« Previous entry: Fresh Veg? | Homepage | Next Entry: Russian Volcano »
Radioactive Camera Lens
Also colloquially “hot glass.” Lens glass which contains radioactive rare earth elements such as thorium (Th).
From the 1940s through to the early 60s lens makers (including Kodak/Aero Ektar, Leitz/Leica, Canon and Pentax/Takumar) sometimes included traces of thorium in certain lens elements because it lowers the refractive index of the glass. And some radioactive contaminants sometimes found their way into (usually non-radioactive) lanthanum (La) compounds used in other types of glass.
If you’re concerned about your old lens or viewfinder (though nearly all commercial lenses built since the 1960s should be free of radioactive materials) you can try putting it on a piece of high-speed film or paper in a pitch-dark place for a week. If the developed emulsion shows fogging you should have the lens tested by a professional with a Geiger counter to determine how radioactive it is.
Posted by mrmule at June 16, 2004 12:41 PM
Trackback Pings
TrackBack URL for this entry:
http://www.mrmule.com/trackback.pl/64
