Nikon f2 - Manual (Page 29)

DEPTH OF FIELD
Depth of field refers to the zone of acceptable focus ex­
tending in front of, and behind, the plane of sharpest
focus. Within this zone, image blur is negligible and
everything may be considered as being in sharp focus.
Three factors greatly influence the depth of field: the
focal length of the lens in use, the camera-to-subject
distance, and the taking aperture. The smaller the aper­
ture and the shorter the focal length of the lens, the
greater the depth of field. Also, the closer the subject,
the shallower the depth of field. These three factors can
operate independently or in conjunction with one an­
other, with any one factor capable of partially canceling
the effects of the other. Thus, by careful selection and
use, the photographer can exercise wide creative control
over the final picture.
Depth-of-Fleld Preview Button
As most Nikkor lenses are operated at full aperture for
ease of focusing, visualization of the depth of field at the
shooting aperture may be difficult. Thus, the camera’s
depth-of-field preview button often can come in handy.
The depth-of-field preview button lets you check (or
“preview”) the zone of sharpness at any time before (or
after) shooting. Simply by depressing the button, the
lens is stopped down to the preselected aperture to allow
you to see how much background and foreground is in
or out of focus.