Canon EOS 30D Instruction Manual page 174

3 Custom Function SettingsN
C.Fn-18
0: AF stop
1: AF start
AF operates only while the AF stop button is pressed. While the
button is pressed, AF operation with the camera is disabled.
2: AE lock
When the button is pressed, AE lock is applied. Convenient when
you want to focus and meter separately.
3: AF point: M 9 Auto / Auto 9 ctr
In the manual AF point selection mode, the button instantly
switches to automatic AF point selection from manual AF point
selection only while you hold it down. Convenient when you are no
longer able to focus track a moving subject with a manually-
selected AF point in the AI Servo AF mode. In the automatic AF
point selection mode, the button selects the center AF point only
while you hold it down.
4: ONE SHOT
In the One-Shot AF mode, the button switches to the AI Servo AF
mode only while you hold it down. In the AI Servo AF mode, the button
switches to the One-Shot AF mode only while you hold it down.
Convenient when you need to keep switching between One-Shot AF
and AI Servo AF for a subject which keeps moving and stopping.
5: IS start
With the lens' IS switch already ON, the Image Stabilizer operates
only while you press the button.
The AF stop button is provided only on super telephoto lenses.
C.Fn-19
0: Off
1: On
Data for verifying whether the image is original or not is appended
to the image. When an image appended with the verification data
is played back, the <L> icon will be displayed. (p.114) To verify
whether the image is original, the Data Verification Kit DVK-E2
(optional) is required.
174
Lens AF stop button function
AI SERVO
Add original decision data