Minolta 35-105MM F3.5-4.5 MD ZOOM - Depth of Field Management; Understanding Depth of Field; Using the Depth-of-Field Scale

DEPTH OF FIELD
When a lens is focused on a given subject,
there is a certain distance range behind and in
front of the point of focus within which the
photographic image will appear acceptably
sharp. This distance is know as "depth of
field", and it varies in accordance with three
factors: Depth of field decreases the longer the
focal length of the lens, the larger the lens
opening used, and the closer the lens is focused;
it increases the shorter the focal length, the
smaller the lens opening used, and the farther
from the camera the lens is focused.
With most Minolta SLR cameras, effective
depth of field may be visually checked by
pressing the depth-of-field preview button and
viewing the subject through the finder with the
lens stopped down to the aperture at which the
picture is to be taken.
Depth-of-field scale
Depth of field may also be determined
approximately from the depth-of-field scale on
the lens barrel. When the lens is zoomed to a
particular focal length and focused at a given
point, the image will be in satisfactory focus
from the nearer value to the farther value on
the distance scale indicated by the depth-of-
field scale lines for the aperture to be used.
The depth-of-field scale can also be used to
zone focus, i.e., set the focusing grip so that
some anticipated action will take place within
the limits of the depth of field.