Canon EOS 5Ds Instruction Manual page 129

Auto AF point selection: EOS iTR AF
EOS iTR* AF executes autofocus by recognizing faces and subject
colors. EOS iTR AF works when the AF area selection mode is set to
61-point automatic selection AF or Zone AF (manual selection of zone).
* intelligent Tracking and Recognition: The function that the metering sensor
identifies the subject to make the AF points tracking it.
In AI Servo AF mode, the camera remembers the color at the position
it focused on first, then continues to track and focus on the subject by
switching AF points to track that color. This makes it easier to keep
track of the subject than when only AF information is available.
In One-Shot AF mode, EOS iTR AF makes focusing on people
easier, so you can perform shooting with priority on composition.
OFF: Disable
AF points are automatically selected based only on AF information.
(The AF will not use information about faces, subject colors and
other details.)
If [Enable] is set, the camera may take longer to focus than when
[Disable] is set.
Even if you set [Enable], expected result may not be obtained depending
on the shooting conditions and subject.
Under light so low that the EOS-dedicated, external Speedlite emits the
AF-assist beam automatically, AF points are selected automatically
based only on AF information.
Face detection may not work if the face is small or under low-light
conditions.
3 Customizing AF FunctionsN
ON: Enable
The AF point is automatically
selected based not only on AF
information, but also faces and other
details.
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