This is a very basic question I have never gotten a good technical answer for.
What makes UD glass so special or expensive? Other L lens attributes such as aspherical or flourite lenses are intuitively obvious since the grinding, molding, deposition or crystal growing techniques are more technically complicated than a regular spherical glass lens. What's the deal with low dispersion glass; do the rare earth additives cost a million dollars an ounce? Is the glass so hard it takes longer to grind? Is it really fragile and hard to handle with lots of scrap? Why can Tokina, Sigma or Tamron put UD glass into a much cheaper lens? Any optical experts out there? Thanks, John Lovda * **** ******* *********************************************************** * For list instructions, including unsubscribe, see: * http://www.a1.nl/phomepag/markerink/eos_list.htm ***********************************************************
