My friend hang over at my place recently, and was interested to know if filter makes a difference. He couldn't believe his eyes.
all shots using Canon 40D + Canon 70-200mm f2.8 IS L
Final result by rank
1) Hoya HD - no noticable flare
2) B+w (Alloy) - slightly flare on lower right
3) Hoya Pro1 - right slide flare
4) No Filter - left side flare
5) Hoya HMC - flare everywhere !
i don't have the brass type of b+w and Heliopan for comparison, anyone would be kind enough to send me one :) hahahaha