Canon EOS 7D Instruction Manual page 211

C.Fn III -4
If autofocus is executed, but focus cannot be achieved, the camera can
either keep trying to focus or stop.
0: Focus search on
1: Focus search off
Prevents the camera from becoming grossly out of focus as it attempts
to focus again. Especially convenient with super telephoto lenses which
can become extremely out of focus.
C.Fn III -5
Normally, this adjustment is not required. Do this adjustment
only if necessary. Note that doing this adjustment may prevent
correct focusing from being achieved.
With setting 1 or 2 selected, press the <B> button to view the register screen.
To cancel all the registered adjustments, press the <L> button.
0: Disable
1: Adjust all by same amount
The same adjustment amount is applied to
all lenses.
2: Adjust by lens
An adjustment can be set individually for
any particular lens. Adjustments for up to 20
lenses can be registered in the camera.
When a lens whose focus adjustment has
been registered is attached to the camera, its point of focus will be
shifted accordingly.
If adjustments for 20 lenses have already been registered and you want
to register an adjustment for another lens, select a lens whose
adjustment can be overwritten or deleted.
Lens drive when AF impossible
AF Microadjustment
You can make fine adjustments for the AF's
point of focus. It can be adjusted in ±20 steps
(-: Forward / +: Backward).
The adjustment amount of one step varies
depending on the maximum aperture of the lens.
Adjust, shoot (73), and check the focus.
Repeat to adjust the AF's point of focus.
3 Custom Function SettingsN
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