Archived posting to the Leica Users Group, 1998/03/12
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]At 01:01 AM 3/14/98 +0100, you wrote: >A question for the cognoscenti among you. The coating on the front element >of my 50 summicron (latest) and 28 elmarit (latest) is red, but that on my >new 90 elmarit is green. Why is there a difference? > >Neil Frankish > Wide angle light is shifted toward blue. Because it's coming in from such an angle, the red component is lost. So red is added via the coating. Telephoto light doesn't get bent so much. It has a fairly straight through path, so no red is added to the normal green coating. Or perhaps, in your case, you bought the 50 & 28 around Christmas time. Leica was in a festive mood. Sorry, the lack of LUG messages this morning made me a little silly. Jim ps... coating is a very complex chemical ion deposition process. The color you see is simply the reflective color of the particular process they used at that particular time. Manufacturers change the make-up of their coating depending upon the season. No no... sorry. They do change coating formula. I'm not sure why, perhaps Erwin can elaborate. :-)