Canon EOS-1D C Instruction Manual page 93

AI Servo 2nd image priority
You can set the AF operation characteristics and shutter-release timing
for subsequent shots during continuous shooting with AI Servo AF.
: Shooting speed priority
Priority is given to the continuous shooting speed instead of achieving
focus. The continuous shooting speed does not slow down. Convenient
when you want to maintain the continuous shooting speed.
: Focus priority
Priority is given to achieving focus instead of the continuous shooting
speed. The picture is not taken until focus is achieved. Effective when
you want to achieve focus before capturing the shot.
3 Customizing AF Functions
: Equal priority
Equal priority is given to focusing and
continuous shooting speed. In low light
or with low-contrast subjects, shooting
speed may slow down.
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