Canon EOS-1D Mark II Digial - AF Sensitivity and Lens Maximum Aperture

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The EOS-1D Mark II’s AF points are all horizontal-line sensitive.
However, bright lenses with a large maximum aperture enable certain
AF points to work as cross-type sensors for higher AF precision.
(1)
With lenses whose maximum aperture is f/2.8 or
larger, the AF points highlighted in the diagram will
work as cross-type sensors sensitive to both vertical
and horizontal lines. The remaining 38 AF points will
only be horizontal-line sensitive. The cross-type
sensor’s vertical-line sensitivity is about three times
higher than its horizontal-line sensitivity.
(2) With the following L-series lenses whose
maximum aperture is f/4 or brighter, the center
AF point will be a cross-type sensor with or
without an Extender attached. The remaining 44
AF points will only be horizontal-line sensitive
(except with EF 70-200mm f/2.8L USM +
Extender EF 1.4x).
· EF 28-80mm f/2.8-4L USM
· EF 300mm f/4L USM
· EF 300mm f/4L IS USM
· EF 400mm f/4 DO IS USM
· EF 500mm f/4L IS USM
· EF 600mm f/4L USM
· EF 600mm f/4L IS USM
· EF 70-200mm f/4 L USM
¡With Extender EF 1.4x or EF 1.4x II:
· EF 200mm f/2.8L USM
· EF 200mm f/2.8L II USM
· EF 300mm f/2.8L USM
· EF 300mm f/2.8L IS USM
· EF 400mm f/2.8L USM
· EF 400mm f/2.8L II USM
· EF 400mm f/2.8L IS USM
· EF 70-200mm f/2.8L IS USM
¡ With Extender EF 2x or EF 2x II:
· EF 135mm f/2L USM
· EF 200mm f/1.8L USM
AF Sensitivity and Lens’ Maximum Aperture