From: Paul Repacholi (prep@prep.synonet.com)
Date: 12/11/01-10:25:24 AM Z
> Scientific graphics supply catalog that all Nikon El Nikor Enlarging
> Lenses were made of a special optical glass to allow passing of UV
> waves between 350 and 450 nm.. I have also read of Sun enlargers
> utilizing sunlight as the light source thru a lens to enlarge during
> the turn of the century in the book "Keepers of Light "...
Bit lefthanded! If you compare BK7 and UBK7 at 350nm, the difference
is 0.93 vs 0.94 for a 25mm section. BK7 is about as 'special' a glass
as the sun rising in the east. Also, UV is normally filtered out in
enlargers as it fogs all 3 colour layers in colour printing. There are
several optical glasses that would kill UV (or even blue!) transmission,
but they are normally not used because of the colour shift.
--
Paul Repacholi 1 Crescent Rd.,
+61 (08) 9257-1001 Kalamunda.
West Australia 6076
Raw, Cooked or Well-done, it's all half baked.
EPIC, The Architecture of the future, always has been, always will be.
This archive was generated by hypermail 2b30 : 01/02/02-04:47:33 PM Z CST