5D3: Best AF area selection mode to use for tracking walking people?

Obviously I want their face to be sharp but I find it very difficult to use the single AF point when on AI Servo mode. I am trying to figure out whether 'Expand AF area: left, right, above, below" (4 point expansion) or 'Expand AF area: Surround' (8 point expansion) is better for such a situation. Also should you go into the menu and change the AF case when doing such tracking? Let me know what you guys think, thanks!

Have a read - http://www.learn.usa.c​anon.com …_multiple_af_po​ints.htmlp

Basically 4/8 points expansion still uses the middle point only to try and achieve focus. All surrounding points are on standby and will only be activated if focus cannot be achieved with the middle point.

'Expand AF area: Surround' - do you mean zone AF?

No I mean the one right before Zone AF, the one that has all 8 points surrounding the middle point (it says its called Surround in the menu). Would Zone AF be better?

Edit: after reading the article it does seem zone AF could be pretty useful when trying to land the face on one of the rule-of-thirds intersections. If I understand correctly, the difference between expansion and zone is that expansion points are on "stand-by" and zone points are all activated ready to focus on the closest subject in the area...hmmmm

thedcmule2 wrote in post #16600995
No I mean the one right before Zone AF, the one that has all 8 points surrounding the middle point (it says its called Surround in the menu). Would Zone AF be better?

Edit: after reading the article it does seem zone AF could be pretty useful when trying to land the face on one of the rule-of-thirds intersections. If I understand correctly, the difference between expansion and zone is that expansion points are on "stand-by" and zone points are all activated ready to focus on the closest subject in the area...hmmmm

Problem with zone is yes it allows the camera to have a much larger area to achieve focus, BUT the camera will decide itself which point or points out of the 12 it will use, focusing on the closest subject in the area like you mentioned, meaning you will most likely lose critical focus and might focus on the forehead/prints on t-shirt etc which will affect the sharpness on face (of course that is subjected to the aperture used, camera to subject distance etc).

4/8 points expansion are more precise as camera is using the middle point in the bunch to achieve focus and will only switch to the surrounding points if required.

I think this sentence in the article sums up zone AF pretty nicely -

"Hawk in flight -
The most critical of professional bird shooters might prefer to keep a single AF point upon the eye of a flying bird, the difficulty of this technique with a bird in flight makes Zone AF a welcome alternative for many photographers."

I am mostly trying to shoot models walking/running towards the camera while I walk/run back - but I am also trying to compose so they are off center.

Do you think the best way to go about this is to choose 8-point expansion, with high burst shooting?

thedcmule2 wrote in post #16601007
I am mostly trying to shoot models walking/running towards the camera while I walk/run back - but I am also trying to compose so they are off center.

Do you think the best way to go about this is to choose 8-point expansion, with high burst shooting?

I personally think 4 points expansion off-center should be enough, but it wouldn't hurt with 8 if you struggle with 4...

I wouldn't use zone af in your situation as your photos might end up looking all 'front focused'