Mick, they are a top Super Tele Lens, great for sports and stuff like that, I was actually eying off one the other day, very popular.
This what Canon has to say.
Super Telephoto Lenses
This high-performance lens was designed with portability and handling ease in mind. One super UD-glass element, whose characteristics are similar to fluorite, and one UD-glass element result in sharp pictures from corner-to-corner.
If you find another at a good price please let me know
The only thing is that they will not auto focus with either the 1.4 or 2.0 extenders attached.
leon
