[Leica] Radioactive lenses

[TDSatty@aol.com]

<<<<<Hold your LTM Summicron over a white piece of paper and look through it. 
 If 
the lens has a yellowish cast, this is most certainly one of the early 
Summicrons in which radioactive thorium was one of the "rare" earth elements 
used in making the glass.  Apparently, this warm yellowish cast is part of 
the decaying process of the thorium.  The radioactivity can actually be 
measured with a Geiger counter.  I don't think its hazardous to your health, 
but it may fog film over time.  And it will certainly impart a warmish look 
to your pictures.>>>>

I hear that the radiation is a primary source of "Bokeh" in older lenses, 
enhancing shadow detail (highlight detail in transparencies) by a process 
similar to pre-exposure, although not recommended for users still in their 
child bearing years, especially if a long strap is used.  Care should also be 
taken to only lift the camera to the eye at the moment of exposure.  However, 
there are no known studies of illness related to ionizing radiation among 
Leica users.

Tom Schofield