Canon EOS-1 - Manual (Page 8)

I. CAMERA FEATURES AND OPERATION 8
One-Shot AF: This mode is intended for use with stationary subjects. It locks focus upon
completion of lens drive, allowing the photographer to recompose if desired. One-Shot
AF is also recommended for maximum performance in extreme low-light situations.
AI Servo AF: This mode is intended for use with moving subjects. It operates
continuously up to the instant of exposure, and it also operates between exposures in
burst mode shooting.
In AI Servo AF, you can tell whether the AF system is tracking the subject by observing
the focus indicator in the viewfinder below the picture area. If the focus indicator does
not light, the system is tracking. If it is blinking rapidly, the system is not tracking.
Please note that this is slightly different from the camera's behavior in One-Shot AF. In
One-Shot, the focus indicator still blinks when the subject can't be focused, but it lights
up continuously when focus has locked.
Canon provides two AF point selection methods: Automatic and Manual. The details of
each method are described below.
Automatic Focusing Point Selection (AFPS): The camera selects a focusing point for
you, choosing from all 45 points. AFPS behavior varies according to your choice of
focusing modes:
• When One-Shot AF is combined with AFPS, the camera typically selects the closest
subject with readable contrast. Since the subject may be large enough to cover several
focusing points simultaneously, the viewfinder’s focusing point display may illuminate
as many as 13 points simultaneously. If focus cannot be achieved, the in-focus
indicator below the picture area blinks.
• When AI Servo AF is combined with AFPS, the camera shuts off all focusing points
except the central one until the subject has been identified. Once the camera has
started to track the subject with the center point, all 45 points are activated and the
camera is able to track movement not only towards or away from the camera, but
anywhere the subject moves within the 45-point coverage area.
Manual Focusing Point Selection (MFPS): The photographer selects the desired
focusing point. When the camera is set to its defaults, only one or two focusing points
are used. (To select 2 focusing points at once manually, use the Quick Control Dial to
scroll up or down from the currently selected manual focusing point. When 2 focusing
points are active, the camera evaluates both and selects the one with the most
reliable subject data. This can come in handy when photographing moving subjects.)
The active area around a manually selected focusing point can also be expanded in two
stages via Custom Function 17. See Custom Functions for details.
AF Modes
AF Point Selection
Methods