Canon EOS 5D Mark II EOS 5D Mark II Instruction Manual - Page 83

S Selecting the AF PointN Lens' Maximum Aperture and AF Sensitivity With lenses whose maximum aperture is larger than f/5.6 With the center AF point, cross-type AF (sensitive to both vertical and horizontal lines) is possible. The remaining eight AF points are horizontal-line sensitive or vertical-line sensitive. With lenses whose maximum aperture is larger than f/2.8 With the center AF point, high-precision, cross-type AF sensitive to both vertical and horizontal lines is possible. The center AF point's sensitivity to vertical and horizontal lines is about twice as sensitive as the other AF points. The remaining eight AF points are horizontal-line sensitive or vertical-line sensitive. * Except with the EF28-80mm f/2.8-4L USM and EF50mm f/2.5 Compact Macro lenses. The Assist AF points used in the AI Servo AF mode are within the spot metering circle and not displayed like normal AF points. They function as follows: : Vertical-line sensitive with f/2.8 and f/5.6 lenses, as with the center AF point. : Horizontal-line sensitive with f/5.6 lenses. 83