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. Specially designed reflectors are able to absorb and dissipate infrared at the fixture before the visible light reaches the stage. The thermal energy is often projected onto the stage with the visible light, and thousands of watts of incandescent lighting can be uncomfortably hot for the actors on stage. In either case, this heat is also emitted from the lamp as infrared light. Incandescent lamps produce light through heating of the filament, while arc lamps produce light through the heating and ionization of a gas. Reflectors can also be used to selectively reduce or eliminate unwanted thermal emission. Parabolic reflectors are used for lights intended to provide an unfocused wash, such as PAR cans. There is no point at which the light converges, so the light is unfocusable. 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. Ellipsoidal reflectors often are used for tight, focusable spots, although they can be used for floodlights, such as in scoops (see below). This focuses the beam of light into a tight beam. 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. Each unit has a characteristic reflector, used in conjunction with the lens (or lack thereof) to create the desired effect. A reflector is located behind or around the light source in such a way as to direct more light towards the lens or opening. The reflector affects the quality and directionality of the light output. The wash lens system casts a diffused wash of light with a softer beam edge. On the other hand, fixtures such as PAR's and Fresnels use wash lens systems. ERS lights and follow spots use these lenses. Instruments with profile lens systems usually have a beam that is narrow and hard edged. Profile Lens Systems and Wash Lens Systems. The lens and the reflector, along with other beam-altering devices, are both considered part of the optics system. 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 opening is the gap in the housing from where the beam of light is intended to come. From left to right: Lamp, Ellipsoidal Reflector, Shutter/Iris Assembly, Fixed Lens, Variable Lens. Some instruments are made from plastic, such as the Selecon Pacific. 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.
Die casting allows for one single, light-weight body that is more economical to produce and use. With the advent of the Source Four, many lighting instruments are being made from die cast metal. Older instruments were made from rolled and machined steel or aluminum. The housing may be designed with specific elements that help reduce heat and increase the efficiency of a lamp.
It comprises all of the exterior of the fixture except for the lens or opening. 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. Stage lighting instruments all have the following components:
Components See the picture at the top of the page for the physical location of most components.