Canon Rumors said:
The new lenses will get a flourite element (FL) as well as a weight reduction...
Gee, it almost sounds like Nikon it trying to catch up to Canon's innovations.
Check out Nikon's glossary. There's an
entry for fluorite (FL) touting it's advantages, but apparently they forgot to update their
entry for ED glass, clearly intended to bash Canon's use of fluorite, where they state, "
In the past, correcting this problem for telephoto lenses required special optical elements that offer anomalous dispersion characteristics - specifically calcium fluoride crystals. However, fluorite easily cracks and is sensitive to temperature changes that can adversely affect focusing by altering the lens' refractive index." Despite that easy cracking and adverse effects on focusing, they're now saying it's great for their telephoto lenses. Way to innovate, Nikon!
Having said that, this is great for Nikon shooters. A friend picked up my Canon 600/4 II and was very surprised to find it weighed the same as his Nikon 500/4.