Learning Event 9
DEFINE DEPTH OF FIELD AND HYPERFOCAL DISTANCE
1. Depth of Field.
Depth of field is the distance from the nearest point
(NP) of acceptable
sharpness to the furthest point (FP) of acceptable
sharpness.
a. When a lens is focused on a nearby object, the depth of field is
short. If the distance setting is increased, the depth of field increases.
This is the reason why it is important to focus more accurately for nearby
objects than for distant objects, when focusing a lens so several objects
that are at different distances, best results are obtained by focusing on a
point one third into the distance between the nearest and farthest point.
Depth of field always ranges from one-third before to two-thirds after the
point focused on (fig 3-9).
b. Depth of field can be computed mathematically or determined by the
depth of field indicator found on the lenses on modern 35mm cameras.
Figure 3-9.
Depth of field
2. Hyperfocal Distance. Hyperfocal distance is the distance from the LENS
to the NEAREST POINT of acceptable sharpness when the lens is FOCUSED at
INFINITY.
a. Applying the hyperfocal distance, a special case of depth of field
is achieved.
Example, when a lens is focused at infinity, the depth of
field will range from the hyperfocal distance, which is at the nearest point
of focus, to infinity.
b. This depth of field can be extended by refocusing the lens at the
hyperfocal distance.
This will move the nearest point of acceptable
sharpness to one half the distance of the point focused on. The depth of
field has now been extended to one half the hyperfocal distance to infinity.
If the hyperfocal distance happens to be 12 feet and the lens is focused at
12 feet, the depth of field would be from 6 feet to infinity (fig 3-10).
c. Hyperfocal distance always includes infinity.
Depth of field may or
may not include infinity.
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