Mikehit said:From my experience with both the 7D2 and (more limited) the 1Dx2, cases don't make a whole heap of difference until your technique is already good enough to have a decent hit rate but my preferred is #2 or #5.
Reading more experience bird-in-flighters, the 4-points expansion assists the main AF point, the 8-point expansion acts more like a zone and more risk of hitting a complex background.
Zone focus in general works best against plain (or very distant) backgrounds but risks picking up the near wingtip as much as the eye/head. If you are as close as you describe, then this could be a reason.
IS on/off is much discussed as is focus/shutter priority, but should not be the primary reason for the hit rate you describe.
When tracking BIF I often think at the time I have got a pretty good tracking sequence then I look at the pictures as a sequence and see that in successive frames the head is all over the place - this is partly due to the high frame rate giving a relatively long black-out time and when the shutter blacks the VF I am losing track of the bird. Maybe it is worth reducing frame rate so you have more 'visible' time - though I have been experimenting with with not closing my left eye (my right-eye is at the VF) and looking at where the bird is going to keep track of it (apparently it takes some learning, similar to jet pilots with their 'heads up' displays).
I know you are a very experienced photographer but it is worth asking - when you see a bird taking off and put the camera to your eye, is the bird on the focus point immediately? Or do you need to adjust? That will take some of the available time to acquire focus.
Thanks!
Reducing frame rate allows more time for focusing, so I will definitely try that next time. What I do is I start to focus on the bird side head while walking towards it, then keep the focus locked and just walk towards them until they finally are fed up with me and fly away. I have great hit rate with for example soccer and birds at a bit more distance and everything else I shoot, so that's why it's a bit frustrating to not get anything with the ducks. They sure are quick and I realize that it as a demanding situation, especially at f2.0, but then again I always shoot wide open and don't experience this bad hit rate with anything else.
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