Canon 2011B002 EOS-1Ds Mark III Instruction Manual - Page 85

S Selecting the AF Point Lens' Maximum Aperture and AF Sensitivity The EOS-1Ds Mark III can execute high-precision AF with lenses whose maximum aperture is f/2.8 or larger. With f/2.8 and faster lenses* With the 19 AF points indicated by , high-precision, cross-type AF (both horizontal- and vertical-line sensitive) is possible. With cross-type AF, vertical-line detection is about 2 times as sensitive as Assist AF points Cross-type points horizontal-line detection. The remaining 26 Assist AF points are horizontal-line sensitive only. * Excluding the EF24mm f/2.8 and EF28mm f/2.8. With lenses whose maximum aperture is f/4 or larger If the maximum aperture of the lens or Extender and lens combination is faster than f/4, the center AF point will work as a high-precision, cross-type point sensitive to both horizontal and vertical lines. The remaining 18 AF points and the 26 Assist AF points work as horizontal- line sensitive AF points. With lenses whose maximum aperture is f/5.6 or larger With lenses whose maximum aperture is larger than f/5.6, all the AF points, including the Assist AF points, will be horizontal-line sensitive only. With lenses whose maximum aperture is f/8 or larger With lenses whose maximum aperture is larger than f/8, AF will be possible with the center AF point which will be horizontal-line sensitive. AF will not work with the other AF points. When the EF70-200mm f/2.8L USM is used with an Extender, use the center AF point only. The other AF points may cause a focusing error. When using the EF24mm f/2.8 or EF28mm f/2.8 lens, the 13 AF points shown on the right can be used as cross-type points. The remaining 6 AF points will be horizontal-line sensitive. 85