Canon EOS-1 - Manual (Page 16)

The autofocus system responds instantly.
The new AF system incorporated
in the EOS-1 has been improved to
meet the high standards of profes­
sional photographers. It’s faster. It
works better under low-light condi­
tions. And it’s more precise.
There are three focusing modes:
1. One-shot AF mode. AF
operation is completed and locked
once in-focus is achieved. When
shooting in this mode, the shutter
will not release until AF is com­
pleted. With evaluative metering, AF
lock and AE lock occur simultane­
ously. Metering continues until just
before the exposure is made when
using spot metering or partial
metering.
2. Predictive AI servo AF mode.
This sophisticated mode enables
focus prediction control for moving
subjects. This involves shutter-
release priority, and during con­
tinuous shooting, the lens is adjusted
for the movement of the subject.
Custom Function No. 4 even allows
for convenient AF lock in servo
mode.
3. Manual mode. A switch on the
lens barrel permits the change from
AF to manual operation. The green
LED indicator in the viewfinder still
lights up to indicate that the subject
is in focus.
The AF system on the EOS-1
focuses even faster than the system
used on the EOS 630. This higher
speed enables AI servo AF shooting
at up to 4.5 frames per second when
using the Power Drive Booster El
plus an ultrasonic motor lens or one
of the newly-developed professional
L series lenses. It’s quick enough to
catch each segment of fast-breaking
action.