(2) The formula for HPD is:
(a) Where
H
=
Hyperfocal distance in feet
F
=
Focal length of lens in inches
cc
=
Circle of confusion (1/1000" for 16mm cameras)
f
=
Aperture (f/stop)
(b) If you have a 25mm lens on a 16mm camera, the HPD for f/5.6 is 10
feet, 2 inches. Therefore, if you focus your lens on 10 feet, 2 inches, (the
HFD), your depth of field will extend from 5 feet, 1 inch (half the HPD) to
infinity.
(c) All of these formulas can also be figured in meters and
millimeters. Keep in mind that focal lengths, distance and cc must all then be
in meters. Do not mix inches and millimeters in the formula.
(3) Using the HFD will allow you to shoot at different distances and
not have to take the time to focus. Time and stress can be your worst enemy
when filming.
Under combat conditions, taking time to focus each shot could
cause you to miss a shot or expose yourself to unnecessary danger.
(4) The following examples in Table 1-1 are representative of HFD and
They can be used for tactical documentation purposes.
For
more critical purposes use the chart that comes with your lens or the formula
for HFD.
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