Canon EOS 5DS Instruction Manual - Page 78

SSelecting the AF PointN Selecting with the Dial Press the button, then turn the dial or dial to select the AF point in the looping sequence shown on the left. When looking at the LCD panel to select the AF point, note the following: Automatic selection , center , right , top If focus cannot be achieved with an EOS-dedicated, external Speedlite's AF-assist beam, select the center AF point. Lens' Maximum Aperture and AF Sensitivity The EOS 5D will execute high-precision AF with lenses whose maximum aperture is f/2.8 or larger. With lenses whose maximum aperture is f/2.8 or larger* With the center AF point, high-precision, cross-type AF sensitive to both vertical and horizontal lines is possible. With cross-type AF, vertical-line detection is twice as sensitive as horizontal-line detection. The other 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. With lenses whose maximum aperture is larger than f/5.6 The center AF point is a cross-type AF sensor. The other eight AF points are horizontal-line sensitive or vertical-line sensitive. The spot metering circle has six invisible Assist AF points (see left illustration) that function in the AI SERVO AF mode. The Assist AF points have the same vertical-line sensitivity as the center AF point at f/2.8, and the Assist AF points have horizontal-line sensitivity at f/5.6. 78