8-10
April 29, 2004
Focusing
Depth of Field and Focus Tracking
Your camera is equipped with autofocus where focusing is automatically
executed. Basics of the relationship between focus, depth of field, and
focus tracking are explained in this section.
Depth of Field
When focusing, consider depth of field. Depth of field is the zone of
sharpest focus in front of and behind the subject on which the lens is
focused. Depth of field varies according to shooting distance, focal length,
and especially aperture.
Smaller apertures (larger f-numbers) produce a deeper depth of field
where the background and foreground become sharper. Larger apertures
(smaller f-numbers) produce a shallower depth of field where the
background becomes blurred.
Similarly, shorter shooting distance or longer focal length produce a
shallower depth of field, and longer shooting distance or shorter focal
length produce a deeper depth of field. Note that depth of field tends to be
shallower in front of the subject in focus and deeper behind the subject.
NOTE: You can confirm the depth of field with the Depth of Field Preview
button (see
page 2-21
).
Focus Tracking
Your camera automatically switches to focus tracking when a moving
subject is detected under the following conditions:
• The Focus Mode selector is set to Single Servo AF (
S
) or Continuous
Servo AF (
C
) and you lightly press the Shutter Release button.
• You lightly press the Shutter Release button or press and hold
when the AE--L/AF-L Button Custom Setting is set to Start (see
page 5-2
).
Focus tracking lets the camera analyze the speed of the moving subject and
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 before the focus detection. Focus locks when the subject stops
moving and the focus mode indicator
appears in the viewfinder.
In Continuous Servo AF, the camera continues to track the subject and
focus is not locked. Tracking occurs even if a subject starts moving in the
middle of focus detection.
