Section II Shooting
272
use, or an adapter connected to a conventional
electronic flash. In either case, the actuating
device is a photoelectric cell that responds to the
bright burst of light from the master flash that is
connected to the camera. The photoelectric cell
causes the slave unit flash to fire instantaneously.
For more complex multiple flash situations,
radio slaves are often used. These consist of a
transmitter unit mounted on the camera, and
receivers used to trigger the flash units. See
Figure 9-57.
When portable flash is the primary source of
light for a portrait, a more pleasing photo can be
taken by using two or more flash units. One of
these will be the main light and will provide the
principal illumination. The second light, called
the fill light, should be adjusted or positioned
to provide about one-half as much light on
the subject as the main light (this topic will be
explored more thoroughly in Chapter 12, Portrait
and Studio Photography). Additional units may be
used for such tasks as lighting the background.
Exposure calculations should be made based on
the guide number and flash-to-subject distance of
the main light.
Calculating exposure is simple: even though
multiple flash “pops” are being used, each part
of the scene is lighted by a single flash (if you are
careful to avoid overlap). Thus, the flash’s guide
number divided by the flash to subject distance
will provide the correct f-stop. For even exposure,
keep the flash-to-subject distance approximately
the same for each separate flash.
Another application of painting with light
is done with a continuous light that is moved
around during a long exposure. A small bright
continuous light source will produce illuminated
lines in the image. See Figure 9-56. If desired,
a large diffused light source may be used to
illuminate the background, such as the side of a
building, during the exposure.
Figure 9-56. One form of light painting is done by using
a small flashlight in a dark space with the shutter locked
open.
Multiple flash
Lighting a large or complex subject can
also be done through the use of multiple flash
units. Since the entire scene is lighted at one
time (unlike the painting-with-light technique),
moving subjects can be captured. Photos of birds
arriving at a nest, or small animals moving along
a forest trail at night are often made using two or
more flash units. The camera and flash units may
be triggered manually, but often are controlled by
a motion sensor or sound trigger.
Sometimes, two or more flash units may
be physically connected with pc cords to fire
simultaneously. A more reliable and flexible
method of control than cord connections,
however, is the use of slave units. These may be
a small flash unit specifically designed for such
Figure 9-57. A radio slave system can be used to
trigger multiple flash units at distances of up to
1600′ . A—Transmitter unit that mounts on camera.
B—Receiver used to trigger flash units. The LCD panels
provide status information on the system, which can
make use of multiple channels for sophisticated lighting
setups. (LPA Design/Bogen Photo Corp.)
A B