Ai Servo Af - Canon EOS 1D Mark III - Digital Camera SLR User Manual

AI Servo AF

Predictive AF can track a subject approaching at about 31 mph
up to about 26.2 ft. away with an EF300mm f/2.8L IS USM lens.
This is the same as with the EOS-1D Mark II
ment in focusing detection performance enables subject
tracking at 10 fps.
During AI Servo AF when the camera is focusing on a subject
and something closer enters the picture, the camera can either start focusing on that
closer subject or ignore it as an obstruction:
• AI Servo AF tracking method > Main focus point priority (C. Fn III-4,0): The camera will
start focusing on the closer subject that entered the picture. When the center AF point
detects that closer subject, the focusing priority will then shift to the main AF point.
• AI Servo tracking method > Continuous AF track priority (C. Fn III-4,1): The camera will
ignore any closer subject entering the picture. The focus-tracking immediately before
the obstacle entered the picture will continue, and the AF point can shift to any other
one while tracking the original subject instead of being fixed at the main AF point.
C. Fn III-3 (AI Servo 1st/2nd image priority) is for setting the priority on focusing or on
the shutter release for the first and following shots during continuous shooting.
0: Focusing priority takes effect for the first shot as well as for the second and following
shots with focus tracking.
1: Focusing priority takes effect for the first shot, and priority on continuous shooting
speed (more than the focus tracking of the subject) takes effect for the following shots.
2: Shutter-release priority takes effect for the first shot (overriding focus). For the following
shots, priority on continuous shooting speed takes effect more than with option 1.
When "Focusing (subject-tracking) priority" is selected and the subject distance changes,
the continuous shooting speed may become irregular. When "Drive speed priority" is
selected, the focusing might be slightly off, but the shooting speed will be fixed. Setting 2
is effective for press photographers who put priority on capturing the moment.
C. Fn III -3 can be set to change operation characteristics when you press the shutter button
completely in one stroke. Settings 0 and 1 are the same as on the EOS-1D Mark II
When focusing is possible, the lens is driven to match the focusing result obtained
immediately before shutter release. After the lens is driven, the picture is taken. If focusing
is not possible, the picture will be taken immediately. With setting 2, the picture will be
taken immediately regardless of whether focus has been achieved or not.
During low-speed continuous shooting, the subject distance can change significantly
between shots. The slower the continuous shooting speed, the more the lens is driven
between shots to detect the subject. Thus, subject tracking is more precise. Also, with the
EOS-1D Mark III, the improved AF computing performance enables the lens to be driven
more to detect the subject than with the EOS-1D Mark II
V. INCOMPARABLE EOS AUTOFOCUS, NOW EVEN BETTER
100
[m ]
. However, improve-
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. AI Servo AF therefore becomes
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20
10
8
1
5 10 50 100 500
Subject's speed [Km/h]
.
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20