Re: [APML] Nikon 600 f/4

[Chris1011@aol.com]

In a message dated 11/5/2001 2:24:37 PM Pacific Standard Time, lthuedk@pe.net writes:


> Their competition have done everything under the sun to achieve
> "Nikon colour balance," including going to fluorite elements.


As a lens designer, I'm not sure what that means. What is Nikon Colour Balance? Sounds like marketing hogwash. 

I don't think Nikon has achieved any great breakthrough in ED glass design. Right now, Ohara FPL53 is the most advanced ED glass in the world next to single crystal fluorite. The difference is very slight. The key to color correction lies not so much in the ED material, but with the mating elements that are chosen to compliment the ED/Fluorite. Your choice of mating elements can result in either a poorly corrected achromat, a middling well corrected apo, or a zero color full spectrum super apochromat. So, saying that a lens contains fluorite or ED means little unless you also specify the mating glass.

Let me say this, there is so little that the scope/lens users know about color correction that it is very easy for slick marketeers to throw meaningless terms out there for you to swallow. Too bad, because lens design is rather straight forward and is well understood by the industry. Glass making is also well understood by those who have some background in glass chemistry and the physics of light.

Roland Christen