Archived posting to the Leica Users Group, 1997/12/18
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]At 11:59 PM 12/17/97 -0500, you wrote: >Chuck Westphal of Canon explained to me that longer lenses with flourite >and other rare earth glass are made to focus past infinity because the >glass can expand in very warm situations, shifting the focus points. I'm >not sure I buy it. It is a well established fact of many manufacturers. And fluorite crystals (they're not glass) do expand a lot more than regular optical glass does with temperature changes. Chuck is a straight shooter, he does not B.S. I know him from many Canon vs. Leica discussions when I was at the University of Missouri. It also helps to focus through the optimal point to watch the focus roll in and out. So some lenses are made that way for that reason. ========== Eric Welch St. Joseph, MO http://www.ponyexpress.net/~ewelch You'll get what's coming to you ... Unless mailed