AI Servo tracking confusion

[gnirtS]

Ive been using the AI Servo tracking function on the EOS 4xx/5xx range for years but never been overly happy with it so ran some tests today.

Quite simply i can focus on an object in the centre point, engage the track BUT if i pan the camera to move that centred object onto one of the other points the camera simply refocusses on whatever is in the centre with it in the new position. i.e. - it doesnt track as such and is simply acting as a continuous centre point focus.

I've tried this with all points selected (the theory being it'll follow to the other points) and with centre point only selected and get the same result on the 450,500 and 550D bodies.

Im i completely misunderstanding how this feature is meant to work or is it just not working as advertised? (or do i need a really big moving object as the gap between the AF points is bigger than the actual object?)

Im assuming the EOS xxxD bodies dont do any sort of predictive/3D tracking?

Any tips for using this more more effectively (other than buy a 7D!)?

 

[artyman]

Well, referring back to my 350D manual, with AI Servo the tracking will start with the centre point, if Automatic AF point selection is in operation and the subject moves away from the centre point, it will still be tracked provide it is under another focus point. With a manually selected focus point, the selected focus point will track it (or not if it loses it )

 

[gnirtS]

Well, referring back to my 350D manual, with AI Servo the tracking will start with the centre point, if Automatic AF point selection is in operation and the subject moves away from the centre point, it will still be tracked provide it is under another focus point. With a manually selected focus point, the selected focus point will track it (or not if it loses it )

That's what it says in the manual but i cant get any of them to ACTUALLY follow an object between points.