SCHOOL OF FILMMAKING
1533 S. Main Street
Winston-Salem, North Carolina 27127
FIM 151 - FUNDAMENTALS OF PRODUCTION AND CINEMATOGRAPHY
Depth of Field
Depth of Field
Depth of field is defined as the range of distance within which all objects will be in
acceptable sharp focus, including an area in front of and behind the principal point of focus.
There will always be more depth of field behind the principal point of focus than in front of it.
SEE FIGURE 1 – ILLUSTRATION OF DEPTH OF FIELD
Depth of field is determined by the following three factors. You must know all of these in order
to determine your depth of field.
1. Focal length of the lens
2. Size of the aperture (f-stop)
3. Subject distance from the camera film plane
In order to find your depth of field for a particular situation you may use the depth-offield tables available in many film books. There are depth of field tables available for a variety
of focal length lenses. When expressing your depth of field, it is always stated as a range from
the closest point to the farthest point and not as a single number. For example, the depth of field
is from 6 feet 3 inches to 11 feet 9 inches. When using depth-of-field tables remember that the
depth of field is different depending on whether you are working with 16mm or 35mm.
Many assistants also use some type of depth-of-field calculator that allows them to dial in
the focal length, f-stop or t-stop, and subject distance and then read the depth of field. Some
types of depth-of-field calculators are the Guild Kelly Calculator for both 16mm and 35mm and
the Samcine Mark II Calculator. And for those of you with a Palm Pilot or similar device, there
is software that calculates your depth of field for you.
The following examples illustrate how the three factors that determine depth of field affect it.
Focal length of the lens:
You have more depth of field with wide-angle lenses than with telephoto lenses at the same fstop and distance.
Example: A wide-angle lens, such as a 25mm, will have more depth of field at a specific
distance and f-stop than a telephoto lens such as a 100mm at the same distance and f-stop.
SEE FIGURE 2 – ILLUSTRATION OF HOW FOCAL LENGTH AFFECTS DEPTH OF
FIELD
1
Size of the aperture or f-stop
You have more depth of field with larger f-stop numbers (smaller aperture openings) than with
small f-stop numbers (larger aperture openings).
Example: A large aperture, such as f 2.8, has less depth of field at a specific distance
than at a small aperture, such as f 8, at the same distance.
SEE FIGURE 3 – ILLUSTRATION OF HOW F-STOP AFFECTS DEPTH OF FIELD
Subject distance from the camera
You have more depth of field with a distant subject than with a close subject at the same f-stop
and focal length.
Example: An object 20 feet from the camera at a specific f-stop and focal length has
more depth of field than an object 8 feet from the camera at the same f-stop and focal length.
SEE FIGURE 4 – ILLUSTRATION OF HOW DISTANCE AFFECTS DEPTH OF FIELD
SPECIAL CASES OF DEPTH OF FIELD
Two subjects in frame at different distances from the camera.
There is a special case of depth of field when you must keep two objects at different distances
from the camera in focus in the same shot. When holding focus on two different objects in the
same scene, one closer to the camera than the other, it is important to remember that you do not
set the focus at a point half way between the two. Because of the principles of depth of field you
should focus on a point that is one third of the distance between the two objects, in order to have
both of them in focus. This principle or theory is usually called the one-third rule. Remember
that this is a theory that does not work in every situation. You should check the depth-of-field
tables or use the depth-of-field calculators to be sure. It will depend on the depth of field for the
one-third point. Check to see if the distance to each object falls within this range. If it does,
then the one-third principle works. If not, you may have to move the objects, change lenses,
change the lighting or only keep one of them in focus at a time. Also, check with the D.P. about
whether you should split the focus or whether you should favor one actor over another in the
scene. The following example illustrates the one-third rule.
Example: The first object is 6 feet from the camera and the second is 12 feet from the camera.
Using the one-third principle set the focus at 8 feet in order to have both objects in focus. The
distance between the two is 6 feet (12 - 6 = 6). One third of this distance is 2 feet (6  3 = 2).
Set the focus at 8 feet (6 + 2 = 8). Using a depth of field table from we can see that this example
will only work for f-stop numbers of 16 or higher.
SEE FIGURE 5 – ILLUSTRATION OF THE ONE-THIRD RULE REGARDING DEPTH OF
FIELD
2
Hyperfocal Distance
Another special case of depth of field is something called hyperfocal distance. The
hyperfocal distance is defined as the closest point in front of the lens which is in acceptable focus
when the lens is focused at infinity(). You must check the depth of field tables to find out
your hyperfocal distance for a given focal length and f-stop. If you set the focus of the lens to
the hyperfocal distance, your depth of field will be from one-half the hyperfocal distance to
infinity. In other words, setting the focus to the hyperfocal distance gives you the maximum
depth of field.
When calculating the depth of field always use f-stops. Depth of field tables and
calculators base all depth-of-field calculations on f-stop numbers and not t-stop numbers. Use the
t-stop only when setting the aperture on the lens.
Don't take the depth-of-field calculations too literally. The focus does not fall off abruptly
at the near and far range of depth of field. It is more of a gradual decrease to where a point that
is sharp and in focus becomes a blurred circle that is out of focus.
OUT OF FOCUS
IN FOCUS
OUT OF FOCUS
FOCUS DISTANCE
DEPTH OF FIELD
FIGURE 1
3
IN FOCUS
WIDE ANGLE LENS EQUALS MORE DEPTH OF FIELD
IN FOCUS
TELEPHOTO LENS EQUALS LESS DEPTH OF FIELD
FIGURE 2
4
IN FOCUS
SMALL LENS APERTURE (LARGER F-STOP NUMBER)
EQUALS MORE DEPTH OF FIELD
IN FOCUS
LARGE LENS APERTURE (SMALLER F-STOP NUMBER)
EQUALS LESS DEPTH OF FIELD
FIGURE 3
5
IN FOCUS
DISTANT SUBJECT EQUALS MORE DEPTH OF FIELD
IN FOCUS
CLOSE SUBJECT EQUALS LESS DEPTH OF FIELD
FIGURE 4
6
12 FT.
6 FT.
POINT OF FOCUS
8 FT.
FIGURE 5
7