Só para completar: tenho Nikon e trabalho com Nikon e com Canon. Daí percebo
que o AF da Canon é mais rápido e preciso. Principalmente os pontos cross
(até pq os não-cross da Nikon é bem fraco em pouca luz).
Canon EOS-1D Mark IV Autofocus vs Nikon D3s
http://mansurovs.com/canon-eos-1d-mark-iv-autofocus-vs-nikon-d3s It's worth noting one other fundamental difference between the AF
system in the D3S and that of the EOS-1D Mark IV. When Nikon focus is out,
it doesn't tend to be way out. More often than not, peak action frames that
are not perfectly focused aren't that blurry, making some of them still viable.
That is, if you're of a mind that it's better to have a slightly soft frame of
a great peak moment than a totally blurry one. The EOS-1D Mark IV, on the other
hand, produces many more frames that are too soft to use for anything, no matter
how sweet the moment.
To sum up, our experience with the D3S' AF system is that it's trustworthy
and dependable enough for us to be confident using it for peak action sports.
Not perfect: it needs to be a bit faster off the line, in addition to the other
quibbles we've mentioned. But it does work as needed most of the time, which
is in stark contrast to the experience of the EOS-1D Mark IV in the last month.