Canon EOS-1D X Mark III DSLR Camera (Body Only) - Manual (Page 371)

Viewfinder Shooting
[ 2]
AI Servo 1st image priority
You can set the AF operation characteristics and shutter-release timing for the first shot with
AI Servo AF.
[ ] Equal priority
Equal priority is given to focusing and shutter-release timing.
[ ] Release
Pressing the shutter button takes the picture immediately even if focus has not been
achieved. Useful when you want to give priority to capturing the decisive moment rather
than achieving focus.
[ ] Focus
Pressing the shutter button does not take the picture until focus is achieved. Useful
when you want to achieve focus before taking the picture.
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