Canon EOS 20D Service Manual page 85

7) Automatic AF point selection
The automatic selection of the AF point in both the One-Shot AF and AI
SERVO AF modes is based on the same algorithm used by the EOS 10D. The
automatic AF point selection speed and AF point selection accuracy (matching
the user's intended subject) are also about the same as the EOS 10D's.
8) AF point selection
The AF point is manually selected with the Multi-controller on the camera
back.
The Multi-controller can be pressed in 8 directions as well as at the center.
After you press the AF point selection button, press the Multi-controller in the
direction of the AF point you want to select. Pressing the Multi-controller at the
center will select the center AF point. And if you press the Multi-controller in the
direction of the currently-selected AF point, automatic AF point selection will be
set (all the AF points will light).
You can also press the AF point selection button and then turn the Main Dial
or Quick Control Dial to select a AF point.
Also, if C.Fn-13-1/2 (AF point selection method) is set, you can skip pressing
the AF point selection button and just use the Multi-controller or Quick Control
Dial to select the AF point directly.
Multi-controller operation
9) AF-assist light
As with the EOS 10D, the AF-assist
light is a series of stroboscopic flashes.
The working range is approx. 4 meters
at the center and approx. 3.5 meters at
the other 8 AF points. In the case of an
EOS-dedicated, external Speedlite, see
Table 006.
Main Dial/Quick Control Dial operation
Fig. 021 AF point selection sequence
Table 006 AF-assist with External Speedlites
Automatic
Speedlite
Selection
SL580EX
550EX
420EX
380EX
220EX
540EZ
430EZ
ST-E2
* Focus can be achieved only with the center AF point.
13
Technical Information
Automatic
AF point selection
Manual Selection
Top/ Left/
Center
Bottom Right
×
×
×
*
×
×
*
×
×
×
*
×
Diagonal
×
×
×
×
×