Still learning to leverage the 70-200

Picked up the 70-200 f4L a few weeks ago and I'm still learning how best to leverage it. Cloudy race days aren't the ideal obviously.

D'ooh!

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D'ooh! x2

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Great battle that went the entire race.

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The framing isn't particularly interesting in most shots but for some reason I find the lower AF point REALLY slow. Center AF + AI Servo and I capture most any shot, using the lower point I manage to get maybe 1 in 5. It seems to hunt focus a lot more. Is there anything I can do to improve that? I try to keep it over areas of higher contrast but that only seems to help a little.