[Brightcolours]

That is fine. Just correcting your post, no reason you would have to want to use old lenses with thorium- or lanthanum oxide glass.

 

Thorium oxide in glass was used in normal and wide angle lenses mostly. Calcium Fluoride (fluorite) has not replaced that, fluorite is mainly used by Canon on tele primes and tele zoom lenses, and lately a few tele primes and 1 tele zoom from Nikon also use fluorite.