and broads can help minimize the problem. On
the other hand, the gentle spill from umbrellas
or softboxes often makes a very agreeable
background light.
Ceiling Bounce
The low ceilings of many interiors can actually
be a plus, because they make it easy to bounce
fi ll light down onto subjects and background.
Too much ceiling bounce, however, puts shadows
under subjects’ eyes and looks like institutional
grid lighting.
Hiding Lights
Small interiors often make it diffi cult to
keep the lights out of the frame. Light stands
work well in front and to the sides of the action
area, where they are safely off screen.
Study your monitor very carefully for cables, which
have a way of creeping into the shot.
Power Supplies
Small interiors are often located in homes or
other private buildings where electrical circuits
are typically only 15 amps, and an entire room
may be served by just one circuit. When working
with inadequate power, high-effi ciency fl uorescent
lamps draw less power per unit output than
halogens. Consider using the compact units
with screw-base lamps, Figure 16-13.
Background Spill
Small interiors make it diffi cult to keep
subject light from spilling onto the background.
Here again, using the more controllable spots
Figure 16-12 This interior has problems with space,
window light, and irregular ceilings.
Figure 16-13 Although it delivers the light output of
375 watts of halogen light, this three-lamp fluorescent
is only 78 watts.
(Equipment Emporium, Inc.)
Calculating Power Draw
The formula says that the amperage (size) of
a power load (in this case, a video light) is equal
to the wattage of the load divided by the voltage
of the circuit, or
It can be difficult to mentally calculate the
amps used by a video light (and hence, the ability
of an electrical circuit to take the load). Although
North American current is nominally 110 volts, the
actual voltage in a particular circuit may range
from 105 to 130, and typically runs around 115–125.
Without troubling to test each circuit, you cannot
tell what its true voltage may be. Also, mentally
dividing by a number like 117.5 volts is not easy.
To solve both problems, divide by an arbitrary
100 volts simply by moving the decimal. For example,
a 750 watt light would draw 7.5 amps (750 watts
divided by 100).
This not only simplifies the head math; it also
builds in an automatic safety factor, since the
nominal amperage will always be lower than the
actual. For example, at a true 110 volts, a 750 watt
light really draws 6.8 amps, not 7.5.
Amps =
Watts
Volts
340 Video Digital Communication & Production