Canon EOS 70DN Basic Instruction Manual page 532

3 Custom Function SettingsN
C.Fn II: Autofocus
C.Fn II -1
0:
Default setting suited for most subjects. Suited for normal, moving subjects.
Locked on: -2 / Locked on: -1
The camera will try to continue focusing the subject even if an obstacle
enters he AF points or if the subject strays from the AF points. The -2
set ing makes the camera track the target subject longer than with the -1
setting.
However, if the camera focuses the wrong subject, it may take slightly
longer to switch and focus the target subject.
Responsive: +2 / Responsive:+1
Once an AF point tracks a subject, the camera can focus consecutive
subjects at different distances. Also effective when you want to always focus
on the closest subject. The +2 set ing makes it quicker to focus he next
consecutive subject than with +1.
However, the camera will be more prone to focus on the wrong subject.
[Tracking sensitivity] is the feature named [AI Servo tracking sensitivity]
in the EOS-1D Mark III/IV, EOS-1Ds Mark III, and EOS 7D.
368
Tracking sensitivity
Sets the subject-tracking sensitivity during AI
Servo AF when an obstacle enters the AF points
or when the AF points stray from the subject.