[Leica] For Noctilux Lovers

["Bud Cook" <budcook@ibm.net>]

From a section entitled "The atlas of optical glasses" in a brochure
entitled "Leica Lenses For Optical Excellence"....

'Leitz glass 900403, the famous "Noctilux glass" that made this f/1 LEICA
lens possible, consists of no fewer than a dozen different ingredients,
including the rare earth element lanthanum.  One kilogram of this glass
costs about $400 (mid 80's?) while the same weight of an ordinary glass such
as BK 7 costs less than $7.  Please note, however, that 900403 glass is
twice as heavy as BK 7, so that the volume of glass in a kilogram that can
be turned into lens elements is only half so great, and the actual price
ratio between these two optical glasses is approximately 100-to-1.'

Bud Cook