Canon EOS-1DX Af Setting Manualbook page 30

Therefore, Case 6 is an effective setting for subjects that
stop and start suddenly, but also have erratic movement
which could happen in any direction, it works during
Auto selection 61-point AF, Zone AF, and AF point
expansion only.
Shooting subjects that are most appropriate for this
setting include rhythmic gymnastics which includes large
movements with complete stops.
Case 6
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A rhythmic gymnast making sudden big jumps can be
captured when shooting with Case 6 which can focus on
subjects with sudden movement, and erratic movement.
Continuous focusing is possible for large movements
and changes in speed.
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