Canon EOS 5D Mark III Instruction Manual (en)

 Selecting AI Servo AF Characteristics (For a Subject)N
Standard setting suited for any moving 
subject. Works with many subjects and 
Select [Case 2] to [Case 6] in the 
following cases: when obstacles enter 
AF points, when the subject tends to 
stray from AF points, when you want to 
focus a subject that suddenly appears, or 
when the subject moves dramatically up, 
down, left, or right.
The camera will try to continue focusing 
the subject even if an obstacle enters the 
AF points or if the subject strays from the 
AF points. Effective when there may be 
an obstacle blocking the subject or when 
you do not want to focus the 
Case 1: Versatile multi purpose setting
Default settings
• Tracking sensitivity: [0]
• Accel./decel. tracking: [0]
• AF pt auto switching: [0]
Case 2: Continue to track subject, ignoring possible obstacles
Default settings
• Tracking sensitivity: 
[Locked on: -1]
• Accel./decel. tracking: [0]
• AF pt auto switching: [0]
If an obstacle gets in the way or if the subject moves away from the AF 
points for a prolonged period and the default setting is unable to track the 
target subject, setting [Tracking sensitivity] to [Locked on: -2] may give 
better results (p.92).