Pro Production: The Essentials Of Stage Lighting

Defining Terminology
Key terms used to describe the quality and characterstics of lights are throw, beam angle, field, field angle, spill and color temperature.

Throw is the distance between the front of a lighting fixture and the object or person that the light shines upon. Just as sound waves follow the inverse-square law, so do lights—a doubling of throw distance reduces the illumination on the subject matter to one-quarter of the intensity.

Beam angle is the shape or angle of the cone of light that emanated from the front of a fixture. Most modern lights express the angle in degrees. A 19-degree beam projects a smaller circle of light on stage than a 36-degree beam angle, and can throw a bit farther for the same wattage because the light is concentrated in a tighter pattern.

Field refers to how the light intensity is spread across the beam. A unit that produces a “hot spot” in the center of the beam has a peak field, and a beam that has even light intensity has a flat field.

Meanwhile, field angle is the beam that emanates from the fixture when it reaches 10 percent of the light intensity at the center of the beam.Spill is the unwanted light onstage, either from venue sources or leaked from stage lighting.

Temperature refers to the “warmth” or “coolness” of colors. A higher color temp will appear “colder” and more toward the white and blue side of the scale than a lower color temperature, which will appear “warmer” or more toward the red side of the scale.

This measurement is stated in Kelvin. Standard incandescent lamps are about 2800 degrees K (they appear orange to our eye compared to daylight) and tungsten halogen lamps (common in stage lighting) are in the 3200-degree K range. Daylight is approximately 5600 degrees K.

While the human eye and brain are good at color correcting, cameras are not and light sources need to be balanced in the same color range when doing film or video or objects and people on camera will appear to change hues as the different lighting sources illuminate them.

Color correction filters can be placed in front of lights to balance the sources. Other filters called gels can be used to color the light beams.

Another light fixture variation is open faced and lens. Open face units basically just contain the lamp in a reflector and direct the light out the open front of the fixture. These are useful in washing a large area with light. A lensed unit offers more control of the light and can focus the beam.

Common Conventional Stage Lighting Units

Scoops: Round, open face units that are used to wash large areas of the stage or backdrops.

Cycs: Short for cyclorama light, these smaller open face units can be sat on the floor or hung from above and are used to light up backdrops or scenery.

Striplights: a.k.a., border lights, these are compartmentalized floodlights that are wired in three or four circuits with each circuit usually gelled to a different color. This allows color mixing over a large area. They are very popular in school theaters for stage color washes, and are often used across the front of performing stages at floor level to provide some up-lighting to remove shadows from the faces of performers.

PARS: Short for parabolic aluminized reflector, PAR cans have been the go to light at concerts for more than 50 years. The “can” is the fixture that houses the bulb or lamp. Each sealed beam bulb contains a reflector, lamp and front lens. Bulbs are available in different sizes, wattages, and beam spreads.

The largest and most common size used in stage lighting is the PAR 64 which is available in 500- or 1000-watt versions. Beam spreads include Very Narrow (NNSP), Narrow Spot (NSP), Medium Flood (MFL) and Wide Flood (WFL). The PAR 56, which is smaller than a PAR 64 is available in 300- and 500-watt versions, and is popular for use in clubs and smaller venues.

ACLs: Short for aircraft landing lights. Exactly what their title implies, these are PAR bulbs that were designed to work on airplanes, providing a bright narrow beam to assist in landing at night. Because they’re only 28 volts, four are wired together in series so that they can work on a 110-volt AC circuit. They’re often used as accent lights onstage at concerts.