When
it comes to stage lighting, the first and somewhat
obvious priority is the light fixtures. Today, there
are dozens of choices a gigging musician can make
about light fixtures. The two most popular types of
stage light fixtures are PARs and Fresnels. Parabolic
Aluminized Reflector (PAR) light fixtures are the
most popular type of light used on music stages. The
biggest reason for this is their relatively low cost
compared with other types of fixtures. PAR fixtures
come in many sizes, with the PAR number relating to
the number of eighth-inch increments in the diameter
of the PAR lamp, inside the fixture. For example, a
PAR 56 fixture has a 7" diameter lamp (bulb)
inside. Lamps for PAR fixtures are usually available
with various grades of narrow (spot) to wide (flood)
light dispersion patterns. For most modest band
stage-lighting needs, a medium to wide flood pattern
is used. PAR fixtures commonly used for stage
lighting are the PAR 56 and PAR 64 types with 300 and 500-watt lamps, respectively.
For a
little more money per fixture, Fresnel light fixtures
offer a more compact light than PAR fixtures, with
the ability to adjust the amount dispersion with one
lamp type. The fixture gets its name from the Fresnel
glass lens mounted on the front, with its circular
serrated pattern for evenly dispersing a wide area of
light. Unlike the PAR fixtures, Fresnels are used
exclusively for washing (flooding) a stage with its
light. Fresnel fixtures come in 6" and 8"
lens sizes, with the 6" the most popular, using
250 or 500-watt lamps.
PAR
and Fresnel fixtures usually come with features on
the lens openings for holding gel frames, gobos and
barn doors. Gel frames are square pieces of tin with
a circular opening that holds sheets of colored gel
plastic, to tint the light. Mainly used with
spotlights, gobos are similar to gel frames except
they're opaque to all light, with the exception of a
silhouette pattern cut in them that's transferred
onto the stage. Barn doors are pieces of sheet metal
that extend out from the fixture to partially block
the conical light beam, for fitting to the stage
area.
Other
types of fixtures like ellipsoidals (lekos), border
lights, scoops, intelligent lights and follow
spotlights are available as your stage lighting
desires expand. Most of these are more expensive
fixtures, with specific purposes that can be added to
the more general purpose PAR and Fresnel fixtures.
As
opposed to theatrical work, stage lighting for
gigging bands requires a portable means of suspending
the light fixtures from the sides or overhead of the
stage. To accomplish this task, tripod-style stands
and webbed metalwork (trussing) are employed. For
smaller lighting setups, a simple tripod with a
matching "T" bar for each side of the stage
may suffice. Optionally, single horizontal bars
attached to the tripod's extendible vertical bar can
be used to hang more fixtures and become a
"light tree." A number of manufacturers
produce these tripod and bar combinations, and even
include accessories for hanging portable dimmer packs
for neat and compact stage lighting.
As
your light fixture needs grow, running trussing
between tripod stands permits an attractive and
flexible means for mounting many light fixtures for
more precise location and aiming. Today, light
trussing is available in a variety of lengths and
shapes with provisions for secure assembly, quick
tear-down, and transportability.
The
ways of getting power to stage lighting hasn't
changed much in about a century of electric lighting.
For light fixtures, three types of power connectors
are in common usage: Edison, Stage Pin, and Twist-Loc
types. The standard and familiar three-prong Edison
plugs and receptacles are the most common for
portable stage lighting. Because light fixtures are
also used in commercial and theatrical settings,
Stage Pin and Twist-Loc plugs and receptacles are
also used. Most people have seen the curved prongs of
a Twist-Loc plug, but fewer still have seen or
noticed Stage Pin plugs and receptacles.
Cables
for conveying AC power from dimmer circuitry to the
light fixture plugs are standard three-wire, stranded
copper conductors similar to types used in extension
cords. The two most popular are the rubber (Type S)
and thermoplastic (Type SJT) jacketed cables. Most
cables for lighting usage are rated for 1,000 watts
and are sized for 16 or 18-gauge conductors,
depending on the length of the cable run. More
professional (and more expensive) cabling will
contain a few more circuits within the cable jacket,
with purpose-built connectors for termination at
dimmer racks and flown stage trussing. Beware when
replacing or rewiring the short cables between a
light fixture and its plug. Do not use standard
insulated wires or cabling since the fixture's heat
requires that special high temperature (Teflon)
wiring be used.
Most
stage lighting is controlled by circuitry units
called dimmers. These dimmers are much more robust
than the household dimmers used for the dining room
table. Multiple dimmer circuits are usually contained
in rackmount enclosures or in compact boxes called
dimmer packs. Dimmer packs will contain power and
controller inputs and one or more dimmer circuit
receptacles. Again, dimmer packs will be available
with Edison, Twist-Loc, Stage Pin, or terminal strips
for connections to cabling. Most dimmer circuit
ratings will be in the range of 600 to 2,400 watts
per circuit.
For
power distribution to dimmer packs, each pack will
have one or two Edison plugs intended to connect to
the venue's receptacles. If you have a pack with two
plugs, connect both plugs into the same duplex
receptacle outlet for safe operation. The reason for
this is that each plug and receptacle connection is
only good for 15 amperes, even if the venue wiring is
12-gauge to the receptacles for 20-ampere
(2,400-watt) service. Dimmer racks are usually
provided with higher amperage connections that demand
more robust connections. Always have a qualified
electrician make the power cabling connections within
the dimmers and racks to assure safety when using the
equipment.
A
dimmer pack also needs the control information for
each dimming circuit. Today, the means of
transferring this information has evolved from
separate 0 to 10-volt analog control signals per
channel to a digital means of setting several dimmers
from a pair of wires. For portable stage lighting,
two digital interface standards have evolved: MPX and
DMX-512. The Micro-Plex (MPX) method is aimed at
low-cost, short-run, dimmer control applications
where standard XLR mic cables can be used with the
dimmers and the controller chained in a way that's
very similar to MIDI communication. Digital Multiplex
(DMX-512) light control protocol is a second standard
that has been adopted by industry professionals for
theater and other live performance events. DMX-512
cabling uses a five-pin XLR format with a balanced
digital transmission similar to MPX, but with
controlled impedance cables for chained connections.
The DMX requires a termination load at the end of the
chain and allows for up to 512 dimmer addresses to be
controlled.
Controllers
for stage lighting come in a wide variety of
configurations, depending on your control
requirements. Bands starting out with stage lighting
may opt for a foot-operated controller box to switch
between a few preset combinations of lighting
(scenes) with blackout (all off) and scene-chase
capability. If you have the luxury of a production
crew (soundman, lightman, roadies, etc.), a more
complex controller can be employed to change scenes
on the fly and aid the performance beyond static
scene arrangements. Better controllers provide more
scenes plus crossfading between scenes and
"bump" buttons to flash on individual
dimmer channels. A good lighting operator can raise
the level of entertainment by providing a little
"light show" performance.
See also: Lighting Tips
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