Hi! Can someone explain to a layman the difference between optics like the Kowa 883 prominar who uses 'real?' flouride and other optics that contains less, or is it another material similar to flouride? I have problems explaining what I mean but I hope you understand me. Thanks!
Kristoffer,
I'm sure there are others here who can understand it and explain it better than I can. A number of exotic optics, I presume including the Kowa use Fluorite in the lens design. Fluorite is Calcium Fluoride which occurs naturally as Fluorspar. It has a very high Abbe number which will result in very low levels of chromatic aberation. However the brittle structure of the mineral means it is difficult to fashion into lenses. Hence the cost. A number of glass companies have designed glasses including some with a high fluoride content with resulting high Abbe numbers and low chromatic aberation as well which are called Extraordinary low dispersion glass, or ED glass. This is now found in more reasonably priced optics. How Fluorite and ED glass compare at the top end of designs I couldn't say, but I'm sure others can.
More detailed explaination can be found easily with a quick search. Eg. Abbe number
http://en.wikipedia.org/wiki/Abbe_number
David
I should have said that a post in the Kowa section of the Spotting Scope forum might be a more productive location for more detailed questions about the 833.
David