>
> BTW if UV rays can pass thru the lenses why Nikon has an
> (expensive) UV lens
> made of crystal elements? I think the answer should be in the wavelenghts,
> but which?
>
> Marco
Normal glass passes 'long wave' UV but not 'short wave'. Shortwave UV is the
most energetic and damaging, but with prolonged exposure longwave UV can
also cause damage (to human eye lenses, dyes, rubber, etc.).
Quartz lenses will pass both long and shortwave UV.
I don't have the wavelength definition of 'long' or 'short' readily at hand.
Most fluorescent dyes respond to longwave UV (the ubiquitous 'black light').
Many fluorescent minerals respond only to short wave UV, and to see them
fluoresce you must use a UV lamp with a special quartz based filter that
blocks visible wavelengths but passes short and longwave UV.
Chip Stratton
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