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Stage Lighting Instrument by jojo

Components of Lighting Instruments

See the picture at top right for physical location of most components

Although lighting instruments may look and operate differently, they all have the following components:

Box/Housing/Can/Case

A metal or plastic container to house the whole instrument and prevent light from spilling in unwanted directions. This 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 piece that is more economical to produce and use. Some instruments are made from plastic, such as the Selecon Pacific.

Lens or opening

Optics of an Altman 1000Q followspot. From left to right: Lamp, Ellipsoidal Reflector, Shutter/Iris Assembly, Fixed Lens, Variable Lens.

The gap in the housing where the light is intended to come out. Many fixtures use a lens to help control the beam of light, though some, such as Parcans and border/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 part of the optics system.

Reflector

This affects the quality and directionality of the light output. An Ellipsoidal Reflector has a lamp set at one focus of an ellipse, bouncing the light and focusing it at the second focus of the ellipse. This allows the light to spot. A Parabolic Reflector has a lamp at the focus of a parabola, bouncing the light in parallel lines away from the reflector. There is no point at which the light converges, leaving an unfocusable light, causing the more flood characteristics. 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 there of) to create the light that a designer may use.

Yoke

Most instruments are suspended or supported by a "U" shaped yoke, fixed to the sides of the instrument providing an axis of rotation. The yoke is connected to the 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.

C-clamp or Hook Clamp

A C-Clamp utilizes a threaded bolt to prevent the clamp falling off the bar and also to prevent the clamp from moving. In Europe, a hook clamp is used. The shape of the hook clamp prevents it from falling off; the bolt stops the clamp from moving. The bolt is hand tightened, and then tightened 1/4 of a turn with a wrench. Once secured, the fixture can be panned and tilted using tension 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 longer arm attached to the light fixture with a C Clamp on the end. This enables the light to be hung to the side of an electric as opposed to below it.

Lamp or arc source

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 halogen gas instead of an inert gas to increase lamp life and output. Fluorescent lights are rarely used other than as work lights (see below) because, although they are far more efficient, they cannot be dimmed (run at less than full power) without using specialized dimmers and they will not dim to very low levels. They also 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), however, 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. When dimming is required, it is done by mechanical dousers or shutters, as these types of lamps cannot be electrically dimmed. 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.

Accessories

Conventional (non-intelligent lighting) 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 metallic gel frames. Other common accessories include gobo holders or rotators, iris holders, donuts, Barn doors and color scrollers

Types of instruments

Floodlights (the intelligent lights) and spotlights (the Source Fours) in use at the USMC museum

Lighting instruments can be broadly separated into two categories: floodlights, which illuminate a wide area, and spotlights (sometimes known as 'Profiles'), which produce a narrower, more controllable light beam. The distinction has to do with the quality of the light produced by the instrument, with spotlights being a potentially tightly focused light, and floodlights being diffuse light. 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.

Floodlights

PAR lights

PAR 64

Main article: Parabolic aluminized reflector light

Parabolic Aluminized Reflector lights, or PAR lights, or PAR cans, are used when a substantial amount of flat lighting is required for a scene. A PAR can is a sealed beam PAR lamp housed in a simple can-like unit. Like an old-fashioned automotive headlight the reflector is integral to the lamp and the beam spread of the unit is not adjustable except by changing the lamp. PAR lamps are widely used in architectural lighting and may often be found at hardware stores. PAR lights have seen heavy use in rock and roll shows, especially those with smaller budgets, due to their low cost, Light Weight, easy maintenance, and high durability. They are often used in combination with smoke or haze machines which make the path of the beam visible. They are also often used as top or side lights in the theatre and for special effects.

All PAR lamps except those with narrow or very narrow lenses produce an intense oval pool of light, some with fixed focus and soft edges. The way to adjust the orientation of the oval is to rotate the lamp/lens.

The "number" associated with a PAR light (e.g: Par 64, Par 36, Par 16) indicates the diameter of the lamp in 8ths of an inch.

4 different beam angles can be obtained on the PAR-64. The beam angle is determined by the lamp. Lamps come in "very narrow" (6 x 12), "narrow" (7 x 14), "medium" (12 x 28), and "wide" (24 x 48). Each angle has two numerical values since the beams are elliptical rather than circular.

PAR 16s are referred to as "birdies".

PAR-bars are aluminum pipes with par cans permanently attached and circuited through the pipe. Par-bars with 4 instruments are often referred to as 4-bars, and par-bars with 6 instruments are referred to as 6-bars.

In 1995 Electronic Theatre Controls (ETC) introduced the Source Four PAR as an alternative to PARcans . The Source Four PAR uses a lamp separate from the lens and reflector assemblies.

Strip lights

Cyc or strip lights

Main article: Striplight

Strip lights, also known as cyclorama or (Cyc) lights (thus referred to because they are good for lighting the cyclorama, a curtain at the back of the stage), border lights or by the brand name codas, are long housings typically containing multiple lamps arranged along the length of the instrument and emitting light perpendicular to its length. Lamps are often covered with individual gels of multiple colors (often Red, Green, and Blue, which, in theory, allow almost any color to be "dialed up") with each color controlled by a separate electrical dimmer circuit. Many striplights use round pieces of glass (called roundels) rather than plastic gels for color. Roundels can sustain heavy use for a long time and are often found in more permanent installations. Varying the intensity of the different colors enables the lighting designer to establish mood or time of day.

Scoop light

See also: Cyclorama (theater)

Scoop lights

Main article: Scoop (theater)

Ellipsoidal Reflector Floodlights, better known as Scoop lights or scoops are circular fixtures that do not have any lenses. They have a reflector at the back of the fixture that directs the light out of the fixture. Since they do not have any sort of lens system they are cheaper than other fixtures. However, the downside of this is that the light cannot be focused at all (even PARs allow more control than scoops). Scoops are most often used to flood the stage with light from above, or to light backdrops. Scoops can have gels affixed. Occasionally they are used as worklights, which are lights used during non-tech rehearsals and during set work.

House lights

Work lights

House lights and worklights

"House Lights" redirects here. For the song by Chuck Berry, see Rock It (Chuck Berry album).

House lights provide light on the theatre's seats and aisles for the audience before and after performances and during intermissions. They are generally incandescent lights, however fluorescent lights or scoops may be used in some instances. House lights are often controlled by dimmers, but are sometimes on simple switches. Worklights provide general lighting backstage or in the house, and are often fluorescent fixtures. Work lights are almost always switched only.

House and work lights are usually off during performances but are occasionally included in the lighting design to establish focus or emphasize plot elements. When the house lights are not on a dimmer, the switch is usually under the control of the stage manager.

LED stage lights

Main article: LED stage lighting

A front view of a Stagebar LED striplight

LED stage lighting instruments are stage lighting instruments that use light-emitting diodes (LEDs) as a light source. LED instruments are an alternative to traditional stage lighting instruments which use halogen lamp or high-intensity discharge lamps. Like other LED instruments, they have high light output with lower power consumption. Most LED fixtures utilize three or more colors (usually red, green, and blue) which can be mixed to theoretically create over 16 million different colors.

Types of LED instruments

LED stage lights come in three main types. PAR cans, striplights and 'moving head' types. In LED PAR cans, a round printed circuit board with LEDs mounted on is used in place of a PAR lamp. Moving head types can either be a bank of LEDs mounted on a yoke or more conventional moving head lights with the bulb replaced with an LED bank.

Uses

LED lighting instruments used on Radiohead's recent tour

LED instruments can and have been used to replace any conventional lighting fixture, and some shows, such as Radiohead's recent tour, have used only LED lighting instruments.. However, most shows use LEDs only for lighting cycloramas, or as top, side, or back light due to their low throw distance. They can also be used as 'audience blinders' (lights pointed directly at the audience from a low angle).

Spotlights

A spotlight is general term for any lighting instrument used in theatre to create a pool of light on the stage. There are many different types of spotlight which break down into three general areas:

Fresnel lanterns or Fresnels (US) are small fixtures giving a soft-edged spot or pool of light. Their name comes from the distinctive ridged Fresnel lens used on the front

"Profile spots (UK)" or ellipsoidal reflector spotlights (US) tend to be longer fixtures containing convex lenses and having a gate at their focal point which enables the insertion of gobos or irises to shape the beam of light. They give a hard edged beam most often associated in the public mind with 'spotlights'. Large versions are operated by a technician as a 'followspot' to pick out performers on the stage.

Pebble Convex lanterns (or "PCs") are similar to Fresnels, but use a plano-convex lens with a pebbled effect on the planar (flat) side, resulting in less "spill" outside the main beam. They are used much more widely in Europe than North America.

Fresnel lantern

Fresnel with lens open to show stepped lens. There is no lamp in the instrument.

Left-Snoot Right-Barn Door

Main article: Fresnel lantern

A Fresnel lantern (UK), or simply Fresnel (US), employs a Fresnel lens to wash light over an area of the stage. The lens is named after French physicist Augustin-Jean Fresnel, and consequently pronounced with a silent "s". The distinctive lens has a 'stepped' appearance instead of the 'full' or 'smooth' appearance of those used in other lanterns. (it was actually built this way so that lighthouses could throw light farther) The resulting beam of light is wide and soft-edged, creating soft shadows, and is commonly used for back light and side light. Another method of controlling the spread of light is to use either a snoot (also referred to as a top hat), which generally limits the light coming out, or a barn door, which allows the flaps to work as though they were shutters on an ERS. (shown on the right) These methods limit light output and keep excess light from spilling into the eyes of audience members.

Fresnels use a spherical reflector, with the lamp at the focus. The lamp and reflector remain a fixed unit inside the housing, and are moved back and forth to focus the light. This is done by a slider on the bottom or side of the lantern, or by a worm track. At very tight focus, the lanterns are the least efficient, as the least light can escape the housing. Therefore Fresnels are not good for tight focus on small areas. They are most often used at medium distances from the stage for area lighting.

Recently, ETC introduced a new lighting fixture, the Source Four PARNel, which joined the ideas of the PAR fixture and that of Fresnels. The fixture is more versatile, allowing for a flood or a softer spot.

Ellipsoidal Reflector Spotlight

ETC Source Four ERS

Main article: Ellipsoidal reflector spotlight

The Ellipsoidal Reflector Spotlight, ERS or Profile(UK), or also PC (French) is the most abundant and (arguably) important instrument type currently in theatrical use. The flexibility of the ERS allows it to fulfill the bulk of lighting roles in the theatre, from broad area lighting to tight specials; from long throws from the back of the auditorium to shin kickers on the stage. They are sometimes known as a Profile Spotlight (in Europe) or by their brand names, especially the Source Four (a popular lantern from ETC) and the Leko (short for Lekolite, from Strand lighting). Although the Source 4 dominates the plots of well-funded theaters, the Altman 360Q and other "Lekos" are still commonly found in many theaters.

The major parts of an ERS light are the casing in which the internal parts are mounted, an ellipsoidal reflector located in the back of the casing, a lamp mounted so the filament is positioned at the rear focal point of the ellipsoid, a dual plano-convex lens (two plano-convex lenses facing each other in the barrel), and at the front, a gel frame to hold the color gel. The light from the lamp is efficiently gathered by the ellipsoidal reflector and sent forward through the gate, shutters and lens system.

A diagram of a Selecon Performance Lighting Pacific Zoomspot

ERS or profile lanterns can have many useful features. One of the most useful is the use of metal shutters at the focal plane of the lens to shape the beam of light. The shape of the beam is round but with the use of the shutters one can limit the beam to avoid walls, pipes in the lighting grid, or the front seats of the audience. Another feature is a gate, again in the focal plane for sliding in metal plates. These metal plates, commonly known as gobos or deckles, can have patterns cut into them, much like a stencil. These patterns are projected onto the stage. An iris can be also be inserted in this position to make the beam smaller in diameter, reducing the light cast without the sharp edges of the shutters. ERS instruments from ETC, Altman, Selecon and a variety of others have interchangeable barrels which can both create a very sharp or very soft beam as well as alter the beam degree, which can range from a narrow, long distance 19-degree spot to a broad and short-distance 50-degree or even 90-degree. The first 90-degree profile lantern was developed by Selecon Performance Lighting as part of their "Pacific" range of products. Since its introduction many other manufacturers have introduced their own 90-degree barrels. There are also 5 and 10 lenses available for many ERS instruments. The beauty of ERS instruments, especially ETC's Source Four line, is that many different "lens tubes" can be used with the same body. This makes them more efficient, since a venue can purchase varying degrees of lenses, while not buying as many bodies. Many manufacturers also produce zooms which offer the ability to change the beam degree, however, with the added zoom lens, the optics are not as High Quality, making them difficult to use for gobos, since the image most likely can not be as sharp as with a fixed angle light. The Selecon Pacific ERS is another innovative ERS. It has an irregular shape, which is because it is designed to reflect light off of a dichroic cold mirror, which has a heat sink to draw heat out of the instrument. This improves shutter, gobo and color gel life, and also can improve the temperature on stage.

In the UK and Australia, the term ERS is not often used. Instead, an ERS is known by its brand name, or called a "profile spot" (after its ability to project the silhouette or profile of anything put in the gate).

Field angle

Field angle is the angle of the beam of light where it reaches 10% of the intensity of the center of the beam. Most manufacturers now use field angle to indicate the spread that the fixture has. However older fixtures are described by the width of the lens x focal length of the instrument. For example, a 6x9 ellipsoidal would have a 6" lens and a focal length of 9". This nomenclature was used because traditionally, the larger the lens, the more light output, however this is no longer true so most manufacturers now identify their fixtures by beam angle and light output. 6x9 Instruments have a field angle of approximately 37. 6x12 instruments have a field angle of approximately 26. A

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