Section II Shooting
250
Zone Focusing
Another type of prefocusing is called zone
focusing, since it covers a wider area. This
makes it a good choice for activities that are less
predictable, such as football, basketball, or soccer.
The first step is to determine the pair of distances
between which you wish to be able to capture
action, such as 10′ and 30′. The area of acceptable
sharpness is approximately one-third in front of
and two-thirds behind the actual point of focus.
Thus, your point of focus should be one-third the
distance between 10′ and 30′ , or at approximately
17′. Once the camera is focused at that distance,
the lens must be stopped down to an aperture
that will provide acceptable sharpness from 10′ to
30′. The camera’s depth of field preview feature
can be used to observe the changes in depth of
field as the lens is stopped down. Once the zone
of focus is established, any action within that
zone will be acceptably sharp, Figure 9-12.
Using Hyperfocal Distance
A similar technique is to set the lens at its
hyperfocal distance, the nearest point that will
be in sharp focus when the lens is focused on
infinity. This distance is different for each f-stop
and each focal length. When a lens is set to its
hyperfocal distance, everything from one-half
that distance to infinity will be in sharp focus.
To find the hyperfocal distance on a lens with
a depth-of-field scale, first align the infinity
symbol (∞) on the focusing mark, as described
in Chapter 8, Making Exposure Decisions. Note
the distance (in feet or meters) shown above the
mark for the appropriate f-stop on the left-hand
scale. This is the hyperfocal distance. Rotate the
focusing ring until the hyperfocal distance is
aligned with the focusing mark. The distance
figure appearing above the appropriate f-stop on
the left-hand scale will be one-half the hyperfocal
distance. Everything from that point to infinity
will be in focus.
Sharp Focus vs. Motion Blur
The preceding sections concentrated on
obtaining photographs where the subject was
sharply focused. Typically, this involves using
shutter speed and focus techniques to “freeze”
the subject’s motion. Completely stopping motion
is not always desirable, however. To convey a
sense of movement, it is often useful to have some
degree of motion blur in the photograph.
Depending on the effect you wish to convey,
the amount of blur may be very slight or almost
total. As shown in Figure 9-13, selecting a shutter
speed fast enough to stop the most important
motion will still allow some degree of blur to
convey movement. Figure 9-14 shows the opposite
effect: conveying a strong sense of motion by
using a shutter speed slow enough to capture
streaks of colored light from moving vehicles on a
city street at dusk.
Figure 9-12. The photographer set a focus zone to
include the area between the free-throw lane lines. This
ensured that any action taking place around the basket
would be in focus. Note that the two players fighting
for the rebound are sharply focused, while those on the
bench are somewhat soft.