(2) The formula for HPD is:
Focal length of lens in inches
(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
(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
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.
more critical purposes use the chart that comes with your lens or the formula