Archived posting to the Leica Users Group, 1997/06/18
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]>I believe that years ago, coating was an >expensive technique. Jim, Early coatings were soft and delicate, and could be easily damaged, even by careful cleaning. This was another reason to leave the front element uncoated. I read an interesting thing the other day, in a book written in the late 50s/early 60s. I had always thought of lens coatings as being primarily for the purpose of controlling reflections and flare, but according to this, the coatings also allow the manufacturer to control color casts. According to the book, most optical glass absorbs some blue light, so a normal, uncoated lens will yield slightly warm colors. According to the book, most lens coatings appear blue or purple because they must compensate for this warming. The absorbtion of blue light varies with the composition of the glass and the number of elements, so a careful manufacturer varies the color of the coating for each lens. There is a good expanation of exactly how lens coatings work on the Contax website: http://www.contaxcameras.com - - Paul