Canon EOS-1Dx Manual Book page 19

AF area selection mode[Auto selection of 61 AF points]
AI Servo AF with all 61 points used for automatic tracking
Ideal for moving subjects that the old AF systems struggle with
One-Shot AF AI Servo AF
When using [One-Shot AF], a single AF point is selected automatically from the
61 points. When using [AI Servo AF], AF starts from the manually selected AF
point and then selects the most appropriate from all 61 points.
Capture the subject with an AF point near
the center, and then by moving the camera
to the left, you can compose a photo with
space on the left side of the frame.
Shooting started by pinpointing focus on the
leader of a cycling road race with a manually
selec ted AF point. While taking continuous
shots, the camera was moved to the left so the
following cyclists on the left of the leader are
r e n d e r e d b e a u t i f u l l y o u t o f f o c u s i n t h e
background.
Hints and tips
With "AI Servo AF" mode, it is possible to
start shooting using a manually selected AF
fram e covering the subje c t. T his make s
continue tracking of the subject easy. For
convenience it is possible to select the same
start position for Single Point AF and 61 Point
automatic selection AF and switch between
the two as required.
When using [Auto selection of 61 AF points]
during [AI Servo AF], focusing will start from
the manually selected AF point, the camera will
the automatically change the AF point selecting
from all 61 points as the subject moves. The AF
points are arranged in a wide area so it is useful
for capturing and tracking of subjects, however,
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depending on the shooting conditions or if the
subject is small, tracking may not be possible so
caution is necessary. [Auto selection of 61 AF
points] is effective when shooting subjects with
movements that cannot be captured with [AF
point expansion] or [Zone AF] (figure skating
jump scenes for example).
Another effective use is when you want to take
action images for publication/articles with lots
of space in the composition for text etc. In the
examples above shooting began by capturing
the targeted cyclist first with a manually
selected AF point (in the center etc.). From
there, while continuous shooting and moving
the camera (lens) to the left or right, it is
possible to position the lead cyclist off to one
side and include a lot of background (focusing
continues to track the cyclist by automatically
switching AF points).
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Blue color of focus point is for illustration.