Re: 18a filter

["R. C. Lacovara" <lacovara@xxxxxxxxxxx>]

Well I concede that, given the curves, and if one can tolerate the stop or 
so loss, I suppose you can use glass lenses.

Bob

At 11:37 AM 1/19/01 -0500, David J. Romano wrote:
>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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