Canon EOS-1DX Af Setting Manualbook page 34

[Locked on] can be effective when an
obstacle crosses in front of the subject
and when focus jumps to the
background,
With the AF Configuration Tool on the EOS-1D X, not
only can you select from Case 1 - Case 6, but three
parameters for each can be adjusted individually.
[Tracking sensitivity] is the parameter that can be set to
track a subject that the AF point had been following
until a different subject (or background) got in the way.
The [Locked on: -2/-1] setting excludes subjects that
come into the AF point as obstacles, and continues to
focus on the original subject . Selecting -2 results in the
targeted subject being tracked for a longer time before
focus changes to subject now in the AF point.
The [Responsive: +1/+2] setting determines that subjects
that come into the AF point are new subjects to be
focused, and quickly focuses. It is also effective when
you want to quickly focus on subjects that are hidden
and appear suddenly.
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