Canon EOS 5D Mark III Instruction Manual (en)

 Selecting AI Servo AF Characteristics (For a Subject)N
Even if the target subject moves 
dramatically up, down, left, or right, the 
AF point will switch automatically to 
focus-track the subject. Effective for 
shooting subjects that move dramatically 
up, down, left, or right. This setting takes 
effect when the following AF area 
selection modes are set: AF point 
expansion (Manual selection 
), AF 
point expansion (Manual selection, 
surrounding points), Zone AF (Manual 
selection), 61-point automatic selection 
This setting is not available with the 
Single-point Spot AF (Manual 
selection) and Single-point AF 
(Manual selection) modes.
Case 5: For erratic subjects moving quickly in any direction
Default settings
• Tracking sensitivity: [0]
• Accel./decel. tracking: [0]
• AF pt auto switching: [+1]
If the subject moves erratically up, down, left, or right, setting [AF pt auto 
] to [+2] may give better results (p.94).