Stage lighting instruments (or lanterns / Luminaires in Europe) are used in stage lighting to illuminate theatrical productions, concerts, and other performances taking place in live performance venues. They are also used to light television studios and sound stages.
Many stagecraft terms vary between the United States and the United Kingdom. In the USA, lighting fixtures are often called "instruments" or "units". In the UK, they are called "lanterns" or "luminaires". This article mainly uses terms common to the USA.
Components
Stage lighting instruments all have the following components:
Housing
The lamp housing is a metal or plastic container that serves as a body for the entire instrument and prevents light from spilling in unwanted directions. It comprises all of the exterior of the fixture except for the lens or opening. The housing may be designed with specific elements that help reduce heat and increase the efficiency of a lamp. Older instruments were made from rolled and machined steel or aluminum; however, with the advent of the Source Four, many lighting instruments are being made from die cast metal. Die casting allows for one single, light-weight body that is more economical to produce and use. Some instruments are made from plastic, such as the Selecon Pacific.
Lens or opening
The opening is the gap in the housing from where the beam of light is intended to come. Many fixtures use a lens to help control the beam of light, though some, such as PAR cans and border or cyclorama lights, do not have any lenses or optics other than the reflector. The lens and the reflector, along with other beam-altering devices are both considered part of the optics system.
Reflector
The reflector affects the quality and directionality of the light output. A reflector is located behind or around the light source in such a way as to direct more light towards the lens or opening. Each unit has a characteristic reflector, used in conjunction with the lens (or lack thereof) to create the desired effect. An ellipsoidal reflector has a lamp set at one focus point of an ellipsoid-shaped reflector that bounces the light and focuses it at the second focus point of the ellipse. This focuses the beam of light into a tight beam. Ellipsoidal reflectors often are used for tight, focusable spots, although they can be used for floodlights, such as in scoops (see below). A parabolic reflector has a lamp set at the focus point of a parabola-shaped reflector that bounces the light in parallel beams away from the reflector. There is no point at which the light converges, so the light is unfocusable. Parabolic reflectors are used for lights intended to provide an unfocused wash, such as PAR cans.
Yoke
Most instruments are suspended or supported by a U-shaped yoke, fixed at two points to the sides of the instrument, providing an axis of rotation. The yoke is connected to a pipe or batten by one of the clamps mentioned below. It may also be affixed to the deck with floor mounts, or attached to the set with a stage screw.
Attachment apparatus
C-Clamps and hook clamps that utilize a threaded bolt to attach to a pipe or batten and to hold the instrument secure. Once secured, the fixture can be panned and tilted using adjustment knobs on the yoke and clamp. In addition, safety cables (a loop of aircraft cable terminated with carabiners) are used to support the lighting instrument in case the clamp fails. A side arm is a metal pole bolted to the instrument with a clamp on the end. This enables the instrument to be hung to the side of an electric as opposed to below it.
Lamp or arc source
Most theatrical lamps are tungsten-halogen (or quartz-halogen), an improvement on the original incandescent design that used halogen gas instead of an inert gas. Fluorescent lights are rarely used other than as work lights (see below). Although they are far more efficient, they cannot be dimmed (run at less than full power) without using specialized dimmers, cannot dim to very low levels, do not produce light from a single point or easily concentrated area, and have a warm-up period during which they emit no light or do so intermittently. High-intensity discharge lamps (or HID lamps) are now common where a very bright light output is required, for example in large follow spots, HMI (hydrargyrum medium-arc iodide) floods, and modern automated fixtures. Because these types of lamps cannot be electrically dimmed, dimming is done by mechanical dousers or shutters that physically block portions of the lamp to decrease output. Some specially-designed fittings now use light-emitting diodes (LEDs) as a light source. LEDs are ideal where an intense but unfocused light source is required, such as for lighting a cyclorama.
Stage lighting accessories
Conventional (non-intelligent) fixtures are designed to accept a number of different accessories intended to assist in the modification of the output. The most common, found on almost all stage lights, is the gel frame holder. The gel frame holder is intended to hold gel, mounted in cardboard or metal gel frames. Other common accessories include gobo holders or rotators, iris holders, donuts, barn doors and color scrollers.
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