Ai servo inconsistency with zone af on canon 5d3

[KKCFamilyman]

also what is a 5k?......

A 5 kilometer running race or run/walk event.

I'm surprised no one has yet answered this question, knowing that the OP was shooting runners seems pretty relevant to the discussion.

Oh thanks well in that case i think my AF settings should be fine for this, i've found this works well for everything i've tried to shoot with servo so have not seen a need to change the setting since getting it setup
check the other factors i've mentioned in your technique if you are still having issues maybe its the gear
i think 1/250 should be fine for runners although i think panning with a much slower shutter speed of say 1/30 would be pretty cool to try too (but get the servo sorted first )
bear in mind my first bleeding edge 5Dmk3 had a faulty AF module and couldnt focus on anything but it was obvious from the get go something was wrong with it as it sucked in single shot servo and everything you can imagine. but they swapped the cameras out and the new one has been good as gold for the last couple of years. My wifes 5Dmk3 also had to go in for a lose connection in the lens mount where when a heavy lens was mounted it would lose connectivity and not focus, canon replaced the lens mount and associated electronics and its all good now. So it CAN be the gear too

hope this all helps KC family man

Thanks
I will try that. Canon ask me to do a focus test with my lens on both bodies to determine body first then maybe lens but maybe. I am just paranoid because I am going on a 10 day trip soon and if
I dont send it in soon then I will have to rent a lens. I have to try that bb af and case 2 settings. Also i will try reducing some of my af options. I know the random test shots were fine and when time came all were just oof to notice. Uggh. Also at the 70mm end all was fine but half a block straight in front of me they were off.

 

[Nelu]

more likely user error
which AF case were you using?

at f9 everything should have been sharp.

Let`s put it this way: f9 will provide a good depth of field but 1/250s is too long of a time for moving subjects, like people running.
I would recommend using f5.6 or f8 and a shorter time, like 1/1000s or 1/500s.
For example for soccer I never go use a time longer than 1/750s and I don`t have any problems with motion blur.
Additionally I would recommend not to use Zone AF at all because the camera will focus on the closest (nearest) subject, which is not always what you want.

Cheers
Nelu