Canon EOS 1DS MARK II 9443A009 Instruction Manual (en)

The EOS-1Ds 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. 
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