Sorry, Its my shorthand for Circular Polarizing filter, it would take the glare/reflections off the visor pretty effectively, giving a much clearer view of the drivers faces.
Ive got one in my 300f2.8is... I had to swap it out on Saturday morning to a 2xND instead as it was letting in too much damn light...
Very inice shots - is this where the crash was ?
Yeah, crash was at Barbon you tube vid here...........1min43secs and you see my legs going rather fast, I turn and keep shooting though !
http://uk.youtube.com/watch?v=USm9A4UhJNc
My gallery now up with the view down my lens, well, until I bailed !
http://www.seeredphotography.co.uk/portfolio31486.html