[OsmosisStudios]

Originally Posted by acedrew

The newer better (7D, 1D MkIV) have sensors that are larger, and in being larger, they are more sensitive to light. working better in the f4.5-5.6 of the 100-400L. So yes, bodies do play a part, and there is some new tech in this area. I'm sure some of it wil trickle down to the lower end cameras in the near future.

Andrew Rodgers
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Admittedly, but it will be no better than another body with an f2.8 lens or, better yet, one of those lovely f/1.2 primes!

As I said, there are too many factors to simply say "this lens will focus faster than this other lens", empirically, across the board.