I have often wondered about the EX finish on Sigma lenses; its black and hard. Reminds me of the Teflon based stuff I used to have sprayed on my 45 colt slides. It was called GunCote and was baked on after being sprayed onto a finely sandblasted surface. (As a hobby I used to customise hand guns, and shoot them.) GunCote could be used on any metal and later I had optical bench parts coated with it. I'm quite sure that lens barrels could be GunCoted. Perhaps its the same stuff?
Don Dr E D F Williams http://personal.inet.fi/cool/don.williams Author's Web Site and Photo Gallery Updated: March 30, 2002
