Re: 18a filter

["David J. Romano" <romano@xxxxxxxx>]

Bob,
I disagree that quartz lenses are necessary for UV photography, at least
general purpose UVA photography. I looked at the graphs at the links you
provided and the spectral transmission curve for the 18A filter falls
within that of glass, probably BK7 glass. BK7 is a typical lens making
glass and at 340 nm transmits about 50%, passing most of the UVA
spectrum. 

To photograph UVB and UVC, one would need quartz lenses. They are
expensive but are available from http://universekogaku.com/new.htm Also,
the sensitivity of of the film must be considered in those cases. 

Dave
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