Canon EOS 5D - Manual (Page 78)

S Selecting the AF PointN
78
Press the <S> button, then turn the
<6> dial or <5> dial to select the
AF point in the looping sequence
shown on the left.
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.
Selecting with the Dial
Lens’ Maximum Aperture and AF Sensitivity
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.
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.