« on: August 03, 2012, 03:24:43 AM »
Last night I finally got a chance to test the AF in low light. I shot a little tennis action with very poor flood lights. 70-200mm 1/1000s, F2.8, ISO12800. IMO this is pretty poor lighting and the AF was incredible. I did not notice any difference when using 12FPS or < 10FPS (I also tried the zone AF, which I never trusted much on the 7D, and it was amazing how the points danced around the players torsos - I was grinning ear to ear). So in a nut shell, I'm very stoked with the AF performance.
I then decided to try and reproduce the H speed AI AF issue, and sure as nuts, in lower lighting situations the 12FPS AI AF just racked the lens back and forth. Switch to 10FPS and locks first time. I got home and tried the 5D II and it also locks first time. This was by no means an extensive test and I did not try and find that exact lighting point where the 12FPS falls apart, but as a reference 70-200, F2.8, 1/80, ISO25800.
So thats +1 with a low light AF gremlin (not that I'll ever shoot in these conditions in AI AF, but still . . . .)
Any thoughts about the metering being 0-20ev and the af being -2ev-20ev ? I can' recall where I read the dx constantly meters the scene in servo which could be a reason?