[Leica] OT: Bubbles in the Rear Element of 1940' - 1950's Lenses

[msmall at infionline.net (Marc James Small)]

<sigh>  After sixty years, why is this STILL an issue?

Well into the 1950's and perhaps afterwards, quality glass firms produced
optical melds which had small bubbles.  Cheaper glasses lacked these
bubbles as they were more homogenous due to the lack of exotic elements.
So, for more than a century, the presence of small bubbles in a lens was a
mark of that lens being made from quality glass.  This has changed due to
modern processing technologies over the past half-century, so that all
glasses now normally lack such bubbles, though I have been advised of a
late Leitz Photar which shows such.

These bubbles do not affect optical performance.  At least, to the level
which us normal darkroom guys can measure. They are simply a mark of
optical excellence.

Mrc

msmall@aya.yale.edu 
Cha robh b?s fir gun ghr?s fir!

NEW FAX NUMBER:  +540-343-8505