Hi, I am having an issue with my 7D when I am using my 70-200mm f2.8L II IS USM when shooting fast moving objects. I do quite a bit of motocross photography and have found since I purchased these two items my keeper rate has skyrocketed, but......if I am tracking a fast moving object as it comes towards me and adjusting the zoom while shooting in AI Servo mode I get the first 4-5 shots in focus but as I wind the zoom level down as the subject gets closer to make sure they're framed correctly I get a couple of shots that are well out of focus. The camera sems to buffer up most times this happens as well.
Is it because I'm asking the camera to do too much at once by altering the zoom while shooting in AI servo mode on continuous high?
Any info would be greatly appreciated