Ano właśnie - piszą tam, że w połączeniu z puszkami poniżej 1D X/5D Mk III, AF nie jest taki jakiego można by oczekiwać...
To be honest, I felt that I had a somewhat better AI Servo in-focus rate when using the original version 1 IS lenses.
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And the good news is that the Canon EF 400mm f/2.8 L IS II USM Lens performs exceptionally well in all regards, including AF, when used in front of the 5D III.