Fluorite Lens

From my own personal experience, this fluorite element(s) can really bring some magic into the photos.

Here is a old list of the lens with fluorite element




And more information about it can be found in Canon's Lens Work (p172), online version here

http://software.canon-europe.com/files/documents/EF_Lens_Work_Book_9_EN.pdf

New EF 800/5.6L IS have two fluorite elements in it!