5DIII AF performance with f4 lenses ?

Started Aug 22, 2012 | Discussions thread
BillyGoatGruff Forum Member • Posts: 93
Re: 5DIII AF performance with f4 lenses ?

z2122 wrote:

I am considering to buy a 5DIII with a 24-105 f4 IS . I have also a 70-200 f4

I will use only f4 glass because the f2.8 zoom lenses are too expensive for me and as I have seen in the user manual the AF of the 5DIII is not working with the full capabilities with f4 lenses that I have or will buy (24-105 f4, 70-200 f4). According to the user manual the center points are much better with f2.8 lenses.

Is there a difference with AF in real life if I use f4 instead of f2.8 glass on the 5D III?

With f/4 lenses, the ONLY thing you don't have working are the diagonal crossed prisms along the middle (hence no double-cross-type AF points along the middle of the frame). But you still get cross-type points all over the frame. It's only at apertures of f/5.6 or smaller that you lose cross-type points at the periphery (but maintain cross-type points along the middle). So basically, at f/4, your AF is AT LEAST as good as the D4's and D800's.

And remember, the D4 and D800 don't even have double-cross-type AF points to begin with!

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