73The EOS-1Ds Mark II’s AF points are all horizontal-line sensitive.However, bright lenses with a large maximum aperture enable certainAF points to work as cross-type sensors for higher AF precision.(1) With lenses whose maximum aperture is f/2.8 orlarger, the AF points highlighted in the diagram willwork as cross-type sensors sensitive to both verticaland horizontal lines. The remaining 38 AF points willonly be horizontal-line sensitive. The cross-typesensor’s vertical-line sensitivity is about three timeshigher than its horizontal-line sensitivity.(2) With the following L-series lenses whosemaximum aperture is f/4 or brighter, the centerAF point will be a cross-type sensor with orwithout an Extender attached. The remaining 44AF 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 USMAF Sensitivity and Lens’ Maximum Aperture
