Lighting equipment
Lighting instruments
In the context of lighting design, a lighting instrument (also called a luminaire)
is a device that produces controlled lighting as part of the effects a lighting
designer brings to a show. The
termlighting instrument is
preferred to light to
avoid confusion between light and light sources.
There are a variety of instruments frequently used in the theater.
Although they vary in many ways they all have the following four basic
components in one form or other:
- Box/Housing - a metal or plastic
container to house the whole instrument and prevent light from
spilling in unwanted directions.
- Light source (lamp).
- Lens or opening - the gap in the
housing where the light is intended to come out.
- Reflector - behind or around the
light source in such a way as to direct more light towards the lens or
opening.
Additional features will vary depend on the exact type of fixture.
Most theatrical light bulbs (or lamps,
the term usually preferred) are tungsten-halogen (or quartz-halogen), an
improvement on the original incandescent design that uses a halogen gas
instead of an inert gas to increase lamp life and output. Fluorescent
lights are infrequently used other than as worklights because,
although they are far more efficient, they are expensive to make dimmed (run
at less than full power) without using specialised dimmer ballasts and
only very expensive models will dim to very low levels. They also do not
produce light from a single point or easily concentrated area, and usually
have a warm-up period, during which they emit no light or do so
intermittently. However
fluorescent lights are being used more and more for special effects
lighting in theaters. High-intensity
discharge lamps (or HID lamps),
however, are now common where a very bright light output is required—for
example in large follow spots, hydrargyrum
medium-arc iodide (HMI) floods,
and modern automated fixtures. When
dimming is required, it is done by mechanical dousers or shutters, as
these types of lamps also cannot be electrically dimmed.
Most instruments are suspended or supported by a "U" shaped yoke,
or 'trunnion arm' fixed to the
sides of the instrument, normally near its center
of gravity. On the end of such, a clamp (known as a hook-clamp, C-clamp,
or pipe clamp—pipe referring to battens)
is normally fixed, made in a "C" configuration with a screw to lock the
instrument onto the pipe or batten from which it is typically hung. One
secured, the fixture can be panned and tilted using tension adjustment
knobs on the yoke and clamp. An adjustable c-wrench, ratchet (US) or
spanner (UK) is often used to assist the technician in
adjusting the fixture.
Most venues ensure crew and performer safety by attaching a safety
cable/chain (a metal wire or chain with a locking carabiner)
to the fixture. In the event that the fixture's clamp(s) were to fail, the
cable would arrest the fall of the fixture before it could come in contact
with a person. Some larger fixtures can weigh over 100 lb (45 kg) and are
suspended very high above performers heads. Many venues place strict
guidelines regarding the use of safety cables.
All lights are loosely classified as either floodlights (wash
lights) or spotlights.
The distinction has to do with the degree to which one is able to control
the shape and quality of the light produced by the instrument, with
spotlights being controllable, sometimes to an extremely precise degree,
and floodlights being completely uncontrollable. Instruments that fall
somewhere in the middle of the spectrum can be classified as either a spot
or a flood, depending on the type of instrument and how it is used. In
general, spotlights have lenses while floodlights are lensless, although
this is not always the case.
The entire lighting apparatus includes the lights themselves, the physical
structure which supports them, the cabling, control systems, dimmers,
power supplies, and the light
boards. (lighting console)
Hanging the lights or
hanging the battons to hang the lights is known as 'rigging'.
