This setting is not what any “normal” person would think. It’s not about how quick the focus tracking is, it’s about what happens when there’s an interruption in the subject being tracked. What happens if something/somebody comes in front of the subject you are tracking? Does the autofocus keeps on tracking the old subject and tries to regain it or does it tries to focus on the new subject?

The setting will depend on the type of photography you are doing and what you are expecting.

  • For team sports like basketball or hockey and you want to keep track of a specific player, I would set the tracking sensitivity of the focus should be mid-slow.
  • For football/tennis were there are huge empty spaces and you want to catch the ball that comes through, I would set the tracking sensitivity of the focus should be mid-slow.
  • For street photography, I like to have the tracking sensitivity of the focus set to mid-slow. If I focus on somebody, and suddenly somebody else walks in front, I don’t want the focus point to change target at the slightest intrusion.
  • The AI Servo tracking only happens when the focus button is pressed, be it the half press of the shutter or the AF-ON button at the rear.
  • The AI Servo tracking only happens in The AI Servo mode (duh!). It does nothing in One Shot AF, since the subject is supposed to be static, there’s nothing to track or interrupt.
  • My preference is for the default setting, in the middle, half way between fast and slow. It gives me the opportunity to choose what I want to do. I can remove my finger from the AF-ON button and re-press to reacquire the target of the focus or keep up with the new target.