Lighting instrument

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 United States, 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 United States.

Stage lighting instruments all have the following components:

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. 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. The first lantern to make use of die castings was the Strand Pattern 23 designed by Fred Bentham in 1953, this small mirror spot enjoyed a 30 year production run and found its way into many British schools, halls and theaters. Some instruments are made from plastic, such as the Selecon Pacific.

The opening of samad 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 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.

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.

...
Wikipedia