ai servo, continuous shooting, 5d2

I was shooting people running towards the camera with the following settings:

ai servo, continuous shooting, small jpeg
av mode, f4, shutter speed between 1/1000 to 1/2000
5d2, 70200 f4 (IS off) on a monopod

I track the runner using the center focusing point, hold the shutter button for 2 sec. 4 out of 5 shots are out of focus, sometimes all are oof. It seems that the ai servo is not focusing continuously - there maybe a 1 sec lag in between. Is that true? If so how to get perfectly focus shots? I used the same setting on the 40d before, and i can get at least 50% of the shots in focus.

Can you do any better with the other camera?

kenwood33 wrote in post #16769202
...It seems that the ai servo is not focusing continuously - there maybe a 1 sec lag in between. Is that true?.

No, it should be focusing continuously in AI Servo. There is no 1-sec lag. There's got to be something else going on here.

Post the series of photos with EXIF so we can see what is going on.
Perhaps the area you are focusing on doesn't have enough texture or contrast.

i don't have the photos as i was shooting for someone else

most of the runners have their bibs in front and i put the middle focusing point to the bib

it happens for about 10 runners

i end up switching to single shot and no longer have out of focus issues

Using back button focus?

Do you literally mean single shot (as oppsoite to continuous drive mode) or do you mean one shot AF?

Its not an issue I've ever had and that's shooting F1 and MotoGP bikes which are travelling a lot faster than humans running.

I've also never held the shutter button down. Maybe that's where the problem lies?

Did you have the extra (invisible and non-selectable) focus assist points enabled within the custom functions?

There are a further 6 focus points available when using ai servo on the 5D MkII, 3 above and 3 below the centre point to help with tracking. They are disabled normally I believe.

Look at the shots on the cameras screen or review them in DPP. That will show the image with the selected AF spot. You may have been missing the body of the runner on those shots. Switching to single shot AF mode for runners coming at you should lower your keeper rate even more. Stick with servo AF. You may have a custom function set wrong or there might be a defect in the body. Does it do this with other lenses too? Perhaps try cleaning the contacts on the lens and body.

One thing I found during the short time I had my 5DII was it tracked much better in Ai Servo if you had the hidden expansion points mentioned above enabled.

Another thing is you might have had priority set to shutter instead of AF(I'm pretty the 5DII also has the setting) so if anything about the scene made tracking hard for the camera it wouldn't slow down to try and get AF.