Nikon N80 - Manual (Page 88)

About Depth, of Field and Focus Tracking
This camera is equipped with autofocus where focusing is
automaticaliy execufed by the camera. Basics of the relationship
between focus and depth of fieid and Focus Tracking are
explained in this section.
■ Depth of field
When focusing, depth of field should be considered. Depth of field is the
zone of sharpest focus in front of and behind the subject on which the
lens is focused. It varies according to shooting distance, focal length and,
above all, aperture. Smaller apertures (larger f-numbers) will produce a
deeper depth of field where the background and foreground become
sharper; larger apertures (smaller f-numbers) will produce a shallower
depth of field where the background becomes blurred. Similarly, shorter
shooting distance or longer focal length will produce a shallower depth of
field, and longer shooting distance or shorter focal length will produce a
deeper depth of field. Note that depth of field tends to be shallower in
front of and deeper behind the subject in focus.
■ Focus Tracking
When the focus mode selector is set to Single Servo AF (S) or Continuous
Servo AF (C) and the shutter release button is lightly pressed or AE-L7AF-
L button (when AF start in CSM I I is selected) is kept pressed, the
camera automatically switches to Focus Tracking when a moving subject
is detected. Focus Tracking enables the camera to analyze the speed of
the moving subject according to the focus data detected, and to obtain
correct focus by anticipating the subject’s position—and driving the lens
to that position—at the exact moment of exposure.
In Single Servo AF, Focus Tracking is activated with a subject that has
been moving in advance to the focus detection, and focus is locked when
the subject stops moving and • appears in the viewfinder. In Continuous
Servo AF, camera continues to track subject (even with a subject which
started moving in the middle of the focus detection) and focus is not
locked.
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