I put this up on a just-previous thread but thought it, maybe, worth one of it's own: A chap who gave us art students a crash coarse in photography (1960s Bristol) believed that old, old lenses aquired a natural coating. I can well believe this ; if you have ever dug up a very old bottle, in the garden, the glass surface has often begun to stratify giving it a rainbow, or even a gold colour,- a perfect looking coating. Any thoughts ? Is this why very old Elmars give such interesting results ? Adrian.