Canon EOS-1DX Af Setting Manualbook page 35

An example where [Locked on: -2/-1] is more
effective
When another player, or a referee crosses in front of the
s u b j e c t a n d f o c u s c a n s h i f t t o t h e f o re g ro u n d /
background
Example where the referee momentarily appears in front
of the player being tracked, then the player appeares
again. With the [Locked on: -1] setting, the referee in
the foreground is not focused on, and the AF system
continuously tracks the player.
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