Stage Lighting Lighting Instruments Floodlights Spotlights

In the pursuit of the Principles of Lighting, the three main Qualities or Properties of interest are:

In addition to these, certain modern instruments are 'movable', referring to motorized movement of either the entire lamp or a mirror placed in front of its outermost lens. These lamps and the more traditional follow spots add Direction to the relevant characterists of light.

It is important to note that the above characteristics are not always static, and it is frequently the variation in these characteristics that is used in achieving the goals of lighting.

The above elements of lighting are primarily the domain of the lighting designerThe role of the theatre lighting designer (or LD within theatre is to work with the theatre director, set designer, and costume designer to create an overall 'look' for the show in response to the text, but bearing in mind issues of visibility, safety and (LD). In consultation with the director and the scenic or stage designer and after watching sufficient late rehearsals, the LD is responsible for providing an Instrument Schedule and a Lighting Plot. The Schedule is a list of all required materials, including gel colors, gobos, color wheels, barndoors and other accessories. The lighting plot is typically a plan view of the theatre in which the performance will take place, with every luminaire marked, including its 'rough' focus (the direction it should be pointing), its instrument number, any color/gobo/accessories required, and the specifics of its connection to the lighting control systems (channel number). These form the basis of the work the Lighting Crew is to undertake, under the supervision of the Head Electrician and the direction of the Crew Chief.

1 Lighting Instruments

There are a variety of instruments frequently used on the stage.

It is important to note that virtually all theatrical bulbs are incandescent. Fluorescent lights are rarely used outside of work lights because, although they are far more efficient, they cannot be 'dimmed' (run at less than full power), they do not produce light from a 'point' or easily concentrated area, and have a warm-up period, during which they emit no light or do so intermittently. Until recently (1990s), carbon arc lampAn arc lamp is a device that produces light by the sparking (or arcing, from voltaic arc) of a high current between two carbon rod electrodes. The rods are touched and then slowly drawn apart; as the rods separate the current is "struck" and arcs across ts were common in high power follow spots. Carbon arc follow spots have been largely replaced by high-intensity xenon or halogen instruments.

All lights are either Floodlights or Spotlights . The distinction has nothing to do with the area covered, but is based upon the presence or absence of a focusing lens or lenses. Lamps that lack a focusing lens or are in a permanent fixed relationship to their lens are Floodlights.

1.1 Floodlights

PAR lights ( parabolic aluminized reflectorA reflector can mean one of several things: a reflecting telescope a device that causes reflection, e. a mirror or a retroreflector a 1981 album by Pablo Cruise.) These resemble car headlights. They possess a lensA lens is: a part of the eye an optical device that may be used in a camera or in a telescope; see lens (optics). the genus of the lentil a science-fictional alien device in E. Smith's Lensman series, which gives its bearer telepathic and other abilities., but it is an integral part of the lamp housing, and its position relative to the filamentA filament is a fine, thinly spun thread, fiber, or wire. Originally the term referred primarily to animal or vegetable structures, but with advances in technology it is frequently used to refer to human-made things including filaments of incandescent lig cannot be altered.

The lamp produces an intense oval pool of light with soft edges. The only adjustment is a knob that allows the lamp unit to be rotated within its casing, thus changing the orientation of the oval.

These types of instruments come in varying diameters, the most common being designated PAR56 and PAR64 the number indicates the diameter of the housing in eighths of an inch (eg a PAR64 is eight inches in diameter).

Because of the lack of control over beam diameter, shape and sharpness, PARs are seldom used in theatre (except for special effects) but are used extensively at rock concerts, especially in combination with smoke/haze machines which make the path of the beam visible.

Strip or Cyclorama (Cyc) lights These are long housings typically containing multiple bulbs arranged along the length of the instrument and emitting light perpendicular to its length. The strip light housing often contains bulbs of multiple colors (usually the primary colors) with each color controlled by a separate electrical circuit. Varying the intensity of the different colors enables the lighting designer to establish mood or time of day.

House lights and Work lights House lights are incandescent or fluorescent floodlights. House lights provide light for the audience before and after performances and during intermissions. Work lights provide general lighting backstage, or in the house. House lights are often controlled by dimmers, but are sometimes on simple switches. 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.

1.2 Spotlights

Fresnels
Ellipsodial Reflector Spotlights
Paralipspheres

Fresnel: Fresnels are typically 6 or 4 inch, referring to the diameter of the lens. The lens is the distinctive ' Fresnel lensA Fresnel lens is a type of lens invented by Augustin-Jean Fresnel. Originally developed for lighthouses, the design enables the construction of lenses of large size and short focal length without the weight and volume of material which would be required' type, with a 'stepped' appearance instead of the 'full' or 'smooth' appearance of other lenses. The stepped nature of the lens causes a corresponding pattern of circles of light, so Fresnel lenses are usually 'stippled' on the flat side. This pattern of small bumps helps to break up the light passing into the lens to smooth out its eventual pattern.

Fresnels use a parabolic reflector, with the filament of the bulb at the focus. Due to this, the bulb and reflector cannot move independently of one another, and remain a fixed unit inside the housing. It is this unit that is moved back and forth inside the lamp to focus the fresnel. This is done by a slider on the bottom of the light, or by a worm track.

Fresnels are not very efficient. The reflector cannot be larger than then lens aperture, and thus all the radiated light that is neither reflected by the parabola behind the bulb or emitted directly through the lens is absorbed by the casing as waste heat. Additionally, the degree to which the lamp may be focused is limited by the length of the housing. The tighter the focus ('spotted in') the less light is able to escape. Thus fresnels are not good for tight focus on small areas. Fresnels also lack internal shutters, and must rely on barndoors, large metal flaps that may be mounted just beyond the color slot at the front of the light. Due to these restrictions, Fresnels are most often used at middling distances for area lighting. Fresnel bulbs are almost always 'base down': mounted with the bulb up.

ERS: The Ellipsoidal Reflector Spotlight is also sometimes known as a 'Leko'. It comes in very many forms, and is the most numerous and important instrument type in use. The flexability of the ERS allows them to fulfill the bulk of the lighting roles in the theatre, from area lighting to close specials, from long throws from the back of the house to shin kickers on the stage.

ERSs may have more than one focusing lens, while all possess internal shutters for cropping the emitted light, and all accept a color gel in front of the lens and a gobo in front of the shutters. ERS's may have bulbs mounted axially, or with the base either up or down (it is important to hang a lamp in the proper orientation). The lenses are smooth and full, not stepped, and it is the lens or lenses that move in the ERS, not the bulb and reflector assembly as in the Fresnel.

The ERS improves over the efficiency of the Fresnel by surrounding the bulb in an ellipsoidal reflector , with the filament of the bulb at one focus and the aperture to the lens housing at the other. The shutters and gobo are ideally in focal point of this apature.

Moving Lights or Intelligent Fixtures: While originally implemented in 1972, the first computer-controlled stage lighting fixtures, called Moving Lights or Intelligent Fixtures, began to gain widespread acceptance in the Concert Industry in the early 1980's. As the digital age progressed, the cost of these fixtures was reduced and they slowly started being used in a more 'traditional' theatrical environment. Intelligent Fixtures are currently used in almost all major theatrical productions.

Usually relying on compact Arc lamps as a light source, these fixtures generally use stepper motors contected to varying internal devices to manipulate the light before it escapes the fixtures front lens.

Examples of internal devices are:

Color wheels with dichroic lenses used to change the color of the beam.
Pattern wheels with gobos used to change the shape of the beam.
Shutters used to 'dim' or 'strobe' the output, automated lens trains used to focus the beam.
Irises used to change the size of the beam.
Gate shutters to 'square off' the beam.
CYM Color-Mixing Wheels using Color-Subtraction technology to vary beam color.
Prisms
Etc.

The majority of these fixtures also use stepper motors to enable movement of the light fixtures output by either moving a mirror which reflects the beam, or by moving the entire fixture lens train. This allows the fixture to cover large areas by varying the X-Y coordinates of the beam. Higher performance fixtures use servo controlled motors for pan and tilt motion.

Moving Lights are controlled in many ways. Usually the fixtures are connected to a Lighting Console, which outputs a control signal. This control signal sends data to the fixture in a usually one of three ways - Analog (which has largely been phased out), DMX (which is the industry standard control protocol), or Ethernet Control (which is still in development). The fixture then takes this signal and translates it into internal signals which are sent to the many stepper motors located inside.

2 Control Tools

Theatrical lighting fixtures are controlled by lighting consoles (in the U.K., "desks") connected to dimmers and, in the case of luminaires and other remotely-controllable fixtures, directly using 5-pin cable through which the DMX protocol is often used.

Lighting Theatre Stagecraft

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