Technical Theatre/Printable version

Technical Theatre

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Lighting for the stage involves manipulating the four major Controllable Qualities of light; Intensity, Color, Direction and Movement; to influence the four functions of stage lighting which are Mood, Selective Focus, Modeling and Visibility.

Four Controllable Qualities of Light

  • Intensity:The intensity of a light source can vary from near total darkness to painfully bright.
  • Color:Nearly any color you can think of can be created through the use of lighting gels or electronic means. Color can be a major player in creating a mood. However, the lighting designer must be careful in choosing colors so that they coordinate with the colors chosen for costumes and set pieces as well.
  • Direction:This is the area from which the light approaches the stage. This is a major contributor to the function of modeling. Light can come from below, directly above or anywhere in between. They can also originate from in front of the actors, behind them or off to a side. Each combination of directions has its unique effect on the highlights and shadows produced.
  • Movement:refers to the changing in the lights whether it be a change in intensity, color or direction of origin.

Functions of Stage Lighting

  • Visibility is the primary function of stage lighting: making sure the audience can see the part(s) of the stage that the director and/or the lighting designer want them to see.
  • The modeling function includes creating a realistic (or intentionally non-realistic) view of the world of the play. This is done by strategically placing lights above, below, to the side, in front and behind the actors. Through the use of the placement of the lights, you can create different types of highlights and shadows on the actors, props and set pieces.
  • Selective Focus is the function of "forcing" the audience to look where it is desired for them to look through the use of high/low intensity and changes in intensity.
  • The function of Mood is both one of the most difficult and at the same time the easiest function to maintain. It is the easiest because it can be done very simply through the use of colors. However, it can also be overdone to the point of becoming cliche instead of allowing the actors and other aspects to contribute to the overall mood of the play.


A Source Four ERS with a warm gel

An Ellipsoidal reflector spotlight or Profile Spotlight (abbreviated to Ellipsiodal or ERS) is a light with a strong, well defined beam, and is very versatile. Leko and Source Four are two of the most common brand names of these lights.

Commonly the light includes:

  • A gel holder
  • A gobo holder
  • Several shutters to shape the beam.
  • An adjustable barrel, allowing a lighting designer to change the size and focus of the light thrown by the unit by changing the distance between the mirror and the smooth, plano-convex lens or lenses
A Leko ERS

There are several advantages of the ERS that make it one of the most common lights in a theatre. Its Ellipsoidal lens means only a 500w or 750w bulb is needed, instead of a 1000w bulb, while retaining the same brightness. Some ERSes, notably the Source Four, also include a dichroic reflector, so the beam is much cooler than other lights. Dichroic reflectors only reflect light from the visible spectrum, allowing infrared (heat) radiation to pass out the back of the light. This prolongs the life of gels and gobos.

Ellipsoidals can have either a fixed field angle, normally from 5° to 50°, or a variable field angle, commonly called a "Zoom". ETC, who manufacture the Source 4, produce a variety of attachments, commonly called "barrels", to change the field angle of the Source 4.

Uses edit

Ellipsoidals can be used for colour washes, with an attachment to change the field angle, but this job is better suited to PAR cans, Fresnels and Floodlights. Ellipsoidals are good for gobo projection, and highlighting actors or scenery on stage. They can also be used to god-spot actors by placing them at a sharp (5° - 10°) angle. This gives the effect of divine intervention, or, if used with a green gel, alien abduction.


1: Cross section of a Fresnel lens 2: Cross section of a conventional lens of equivalent power

A Fresnel lantern is a light which makes use of the Fresnel Lens, named after Augustin-Jean Fresnel. The lens has a stepped appearance, instead of a round, smooth one. This allows the lens to have a much greater curvature than would otherwise be practical.

Theatrical Fresnels are typically made in 8, 6 or 3 inch varieties, referring to the diameter of the lens, with lamps ranging in wattage from 150 W (typically with a 3-inch fresnel) to 2000W (with an 8-inch fresnel). Fresnel lenses can operate close to the light source and are very cheap to produce, so the lanterns tend to be small and cheap.

Unfortunately, Fresnels are not very efficient. The reflector cannot be larger than the lens aperture, and thus all the radiated light that is neither redirected forward by the spherical reflector behind the bulb or emitted directly through the lens is absorbed by the casing as waste heat.

Uses edit

The stepped lens gives the beam a very even spread of light, compared to an ERS, and this makes them useful for color washes or back- or top- lighting. They are best used at a medium throw. The lack of beam control can be combated by the use of barn doors.


A Parabolic Aluminized Reflector luminaire

PAR lights, or Parabolic aluminized reflector light, are often referred to as Parcans. They are normally a single lamp/reflector unit, that looks similar to a car headlight inside a metal can, which has the appearance of a sausage. Parcans can come in a variety of different sizes, anywhere between a Par16, which is based around an MR16 lamp and the whole unit is approximately 3 inches long, to a Par64, which utilizes a much bigger lamp and is around 2 feet long.

The number following PAR [PAR 64, 38, 16 etc] refers to the diameter of the lenses of the lamp. The formula being n/8 inch = diameter. [ie: a Par64 is 8 inches in diameter]

Parcans have a much greater usage outside of the theater industry, and are used large amounts for music concerts and tours. If large areas need to be lit, a 3 x 3 grid of Parcans is useful, which is known as a "nine-light".

It is now possible to get LED PARs, which are very similar to Parcans, except, instead of using halogen lamps, they use LEDs, to output light, most also have three different color LED's: Red, Green and Blue allowing color mixing to some extent as well as white.

Lamps edit

Parcans cannot be focused, but you can change the beam angle by changing the lamp. You can get lots of different bulb sizes for them, and some of the most common are show below:

  • CP60 - 1000 W, 240 v - VNSP (Very Narrow Spot)
  • CP61 - 1000 W, 240 V - NSP (Narrow Spot)
  • CP62 - 1000 w, 240 V - MFL (Medium Flood)

See /Lamps for more information

Uses edit

Parcans don't have any methods of focusing, and limited methods of beam shaping; as such, they are mainly used for color washes, instead of tight focused areas. They can also be used effectively for blending colors. Their fast flash time makes them good for chase sequences.


A Followspot is a powerful theater light used to 'follow' actors around the stage. They are operated by a human followspot operator. Most followspots use arc lamps or the more powerful xenon arc lamps to produce a bright, white light. Typically followspots include:

  • A powerful lamp
  • A manually focused lens
  • A manual dimming device
  • An "iris" to adjust the size of the spot/angle of the beam
  • A color magazine or "boomerang" consisting of several gel frames which can be swung in front of the beam
  • Some sort of physical sight to assist in aiming is sometimes added onto the lamp by the operator.

Some followspots also allow gobos to be fitted.

Uses edit

Generally a followspot is used to highlight actors on the stage, but it could also be used to focus the audiences attention on a hand-motion or props.

Lighting/Automated Lights

Automated lighting is very popular within the industry because of how versatile it is. Instead of having to rig and focus many generic (non-automated) fittings with different coloured gels or gobos, designers can now use one light to get the colours they desire, with the benefit of having many more features. (Such as gobos, the ability to move the lights for visual effect.) Combining the differing properties in different ways gives the user the ability to create different looks, feel and effects using just one fitting. Originally, automated lights were commonly known as "intelligent" lights. Many in the lighting industry felt this was mis-leading as this type of fitting does not do any "thinking", they do what they are "told" to by the control desk. This is done via the DMX512 protocol.

Operation edit

Almost all automated lights have many and various functions and capabilities. For example, an automated light might have several different colours, pan and tilt functions, zoom, gobos, and shutter options. Usually each of these properties is assigned a DMX512 channel by the firmware in the light itself. Eg.


+0 = Intensity (Usually achieved with a shutter.)
+1 = Colour (Usually, dichroic glass colours placed on the outside of a wheel.)
+2 = Pan (Side to side movement.)
+3 = Tilt (Up/down movement.)
+4 = Gobo (A beam shaping device.)
+5 = Zoom
+6 = Focus
+7 = Control (Lamp ON/OFF, Reset.)

Firstly, the fitting must be assigned a DMX number, eg 10. This means when the control desk changes the value of channel 10, the intensity of the light (shown as an example above) will change also. Channel 11 will change the colour, 12 will make the light move left and right, 13 will tilt the light, 14 will change the gobo and 15 will change the zoom.

Exactly how the changes are made and to what degree vary from light to light, manufacturer to manufacturer.

Pros edit

There are many pros to using automated lighting:

  • Time saving:
    • Focus can be done from the desk.
    • Fewer fitting required to rig as gobo washes or specials.
    • Fewer power cables to run.
  • Aesthetics:
    • Far more looks available to the operator or designer, this is the major reason for using them.

Cons edit

There are also a few cons to consider:

  • Expense: automated lighting costs far more than generics to purchase or hire. An experienced technician is required to program automated lights.
  • Weight: usually far heavier than an average generic.
  • Reliance on a DMX chain: one malfunctioning DMX lead can prevent an entire rig from functioning.
  • High maintenance: automated lights have many moving parts and so require a good maintenance schedule.


Floodlights are basic theatrical lighting instruments, consisting of primarily of a reflector box and a lamp, usually attached to a yoke to allow the instrument to be hung. They are often used in the theater for color washes, or left uncolored for use as work lights. They offer practically no control of the beam or focus. Gels placed over a floodlight tend to fade quickly because floodlights generate a great deal of heat. However, floodlights tend to be among the least expensive lighting instruments due to their simple construction and few complicated parts.They are also used in football games,cricket games,netball games and many more.


Strobe Lights are lights which produce a quick flash of light. They can be used to simulate lightning, or to give the effect of slow motion. They are normally powered by an Xenon flash lamp.

Strobe lighting can trigger seizures in photosensitive epilepsy.


The cyc light is a single unit with asymmetric distribution for even coverage of backcloths and cycloramas. There are many occasions when a broad light source resting on the floor is needed, lighting upwards to illuminate a drop, cyc, or groundrow. The light shades off towards the top, providing an attractive decorative effect. Make Type Wattage

Strand Coda 500W

Strand Iris 1000W

Altman Focusing Cyc Light 500-1500W

Altman 6' 3-Circuit Zip Strip 750W / Circuit

Strand R40 Strip 500W / Strip


Gels, are the coloured 'filters' placed in front of the lights found in theatres, so to colour the beam. Gels are referenced and referred to by number or a letter and number combination. The numbers correlate to a specific color. Since the numbers are assigned by the manufacturer, and are not interchangeable between brands, if gels from multiple manufacturers are present in one shop they will be marked with a letter before the number; typically an R for Roscolux, and L for Lee Filters or an A for Apollo. Three of the most common manufacturers of gels, Lee Filters, Roscolux, and Apollo manufacture 'swatches'. These are packaged as small books with samples of all the different gel colors, allowing lighting designers to sample different gels. You can also obtain a color equivalancy chart from the manufacturers that compares the different manufacturers number systems relate to the color of the filter.

History edit

Gels were originally made out of gelatine. "Gelatine" was shortened to "gels". How and when this occurred is not known. Today, gels are made from a mylar-like polyester. However, the term "gel" remains in common usage. The more correct term color filter, sometimes shortened to color, is also used to refer to these filters.

When gels were made of gelatine, many lighting rookies were given dusty gels that they were to get clean by rinsing in hot water. When they came back, some came back smiling and others came back horrified, convinced that they had done something wrong.

Usage edit

Gels are normally placed in a "color frame", which is a metal or flame-retardant paper frame that holds the gel. This ensures the gels do not wrinkle from the heat as much as they would otherwise and also that they do not bend and fall out of the light. Metal frames are used in most applications because they are more sturdy, and last longer. Paper frames are sometimes used in positions where the lighting instrument will be placed above the audience. The frames are put into the color frame slot at the front of the lighting instrument to color the light.

During use, gels wrinkle and eventually burn through after being used for some time. This is due to the large amount of heat coming out of the luminare and going into the gel. Gel color determines how quickly the gel wrinkles and 'burns-through', with the rate depending on how much heat is concentrated on the gel. Darker colors, which have a lower rate of transmission, mean that more light is stopped from going through, resulting in more heat, and shorter lifespans.

Related Links edit


A gobo

A Gobo (derived from Go Between or Goes Before Optics) is a thin piece of metal, wood, or glass used to used to modify the shape of the projected light. It is generally used with Ellipsoidal Reflector Spots, which normally provide a specific slot for gobo use. Old soda cans make a cheap replacement for custom made metal gobos, but don't last as long as professionally made gobos.

Plastic gobos—which are generally custom made—are available when a pattern is needed in color and glass does not suffice. However, these thin plastic films generally need to be used with special cooling elements to prevent melting them. A lapse in the cooling apparatus, even for just a few seconds, can cause an expensive gobo to be ruined.

Glass gobos can become very complex, and can make use of coloring, much like a stained glass window.

Most manufacturers produce a swatch book of their gobos, and like gels they are referred to by a number rather than name. For example, most manufacturers offer a gobo of a window, but they are all slightly different. So instead of calling it window, it would be identified as gobo 77143 [1]

Lighting/The Designer

The lighting designer, or LD, is responsible for the creative aspect of the electrics team. They decide how much light, with what colors, and textures, from what angles, and so forth are needed. The LD must coordinate with the director, and other designers, to create the look, feel, mood, etc. of the show, and then make those ideas a reality through lighting.

Depending on the size of the company what is expected of a designer can vary greatly. In larger shows the LD will have an assistant, who often does most of the technical drafting, a Master Electrician, who is responsible for making that drafting a physical reality, and a lighting console programmer, who controls the actual lights, through control software, to the designers will. Any or all of these jobs can fall to a lighting designer in smaller companies, taking him away from the creative element of the show and into the technical details.


Introduction to Lighting Control edit

Lighting control refers of any changes made in the light produced by one or more lighting instruments. This includes (but is by no means limited to) changes in intensity, color, direction, diffusion, polarization, and pattern. Though various methods of controlling these variables have evolved over time, it is common to manipulate them all from a central control board. The control board typically communicates with a system of dimmers, which control how much electricity flows to each light, as well as with any individual lights that can mechanically move/change color/rotate/etc. Such lights are usually referred to as intelligent lights.


Dimmers are mechanical or electromechanical devices used to vary the amount of electrical power being sent to each lighting instrument. In most modern theaters, changing the dimmers' output is the primary means of controlling the intensity of the lighting on stage.

The construction of dimmers has evolved considerably over time. Some of the oldest dimmers used in the theater, known as 'salt water dimmers,' consisted of a glass jar filled with salt water with two metal leads placed inside. When this was wired in series with the light to be controlled, an operator could control the light's output by varying the distance between the leads. This was a difficult (and often hazardous) process.

Modern dimmers are much more technically complex, and a great deal safer. They control the amount of voltage in the circuit using thyristors, simple electronic circuits that rapidly turn themselves on and off, allowing precisely the amount of current needed to pass through.


DMX512, is a control protocol, used in most theatres to control dimmers and intelligent fixtures. DMX, is the replacement of AMX192 which is an analogue system that is based around using a voltage difference between 0-10V to control lights. DMX 512, has many advantages over the old AMX system: DMX, can be used to control intelligent moving lights, and is much easier to interface with computer based systems.

The DMX system consists of what are referred to as channels, and the value of each channel varies from 0 to 255. However in the case of a dimmer, this would normally be changed on the controlling device so that the brightness was displayed in a percentage form. Each XLR cable run, can carry up to 512 channels, hence DMX is referred to as DMX512.

DMX 512, works on a system of highs and lows, and packets of data; these packets that tell the fixture or dimmer what to do and are refreshed as soon as the last packet has finished being interpreted. When there are no channels transmitting data in what is known as a 'no-data' situation, the DMX control device will output a continuous high signal. At the start of the next DMX packet, there is a Break, and this is then followed by the Mark After Break, this followed in turn by the Start Code and this again followed by the Mark Time Between Frames which is followed by the Channel Data, which is finally followed by the Mark Time Between Packets.

DMX can be transferred through various cable types, the three most common, are XLR5, XLR3 and RJ45 Ethernet. Originally the standard was XLR5, as whilst DMX only utilised 3 wires, there were two extra cores, to allow for possible expansion, and also separate DMX cable, from microphone cable. However more recently, many manufacturers have started using XLR3 connectors as it allows the utilisation of microphone cable, which is often more easily available. RJ45 ethernet connectors began to be used, as it allowed the networking of all DMX devices, as both lighting desks, dimmers and some newer intelligent fixtures began to have networking capability, a feature which could be found extremely useful in larger theatres.

More information regarding DMX, can be found on the U.S. Institute of Theatre Technology's website, as DMX512 is based on their standards


Inputs for a sound system would include microphones (specific types are discussed in another section), Compact Disc Players, Tape Players, Record Players, DVD Players, Video Tape Players and computers. Basically, anything that pushes sound into the front end of a sound system would be considered an input.


Dynamic Microphones Dynamic microphones are versatile and ideal for general-purpose use. They use a simple design with few moving parts. They are relatively sturdy and resilient to rough handling. They are also better suited to handling high volume levels, such as from certain musical instruments or amplifiers. They have no internal amplifier and do not require batteries or external power.

How Dynamic Microphones Work As you may recall from your school science, when a magnet is moved near a coil of wire an electrical current is generated in the wire. Using this electromagnet principle, the dynamic microphone uses a wire coil and magnet to create to create the audio signal.

The diaphragm is attached to the coil. When the diaphragm vibrates in response to incoming sound waves, the coil moves backwards and forwards past the magnet. This creates a current in the coil which is channeled from the microphone along wires. A common configuration is shown below.

Earlier we mentioned that loudspeakers perform the opposite function of microphones by converting electrical energy into sound waves. This is demonstrated perfectly in the dynamic microphone which is basically a loudspeaker in reverse. When you see a cross-section of a speaker you'll see the similarity with the diagram above. If fact, some intercom systems use the speaker as a microphone. You can also demonstrate this effect by plugging a microphone into the headphone output of your stereo, although we don't recommend it!

Technical Notes:

Dynamics do not usually have the same flat frequency response as condensers. Instead they tend to have tailored frequency responses for particular applications.

Neodymium magnets are more powerful than conventional magnets, meaning that neodymium microphones can be made smaller, with more linear frequency response and higher output level.


Condenser Microphones Condenser means capacitor, an electronic component which stores energy in the form of an electrostatic field. The term condenser is actually obsolete but has stuck as the name for this type of microphone, which uses a capacitor to convert acoustical energy into electrical energy.

Condenser microphones require power from a battery or external source. The resulting audio signal is stronger signal than that from a dynamic. Condensers also tend to be more sensitive and responsive than dynamics, making them well-suited to capturing subtle nuances in a sound. They are not ideal for high-volume work, as their sensitivity makes them prone to distort.

How Condenser Microphones Work A capacitor has two plates with a voltage between them. In the condenser mic, one of these plates is made of very light material and acts as the diaphragm. The diaphragm vibrates when struck by sound waves, changing the distance between the two plates and therefore changing the capacitance. Specifically, when the plates are closer together, capacitance increases and a charge current occurs. When the plates are further apart, capacitance decreases and a discharge current occurs.

A voltage is required across the capacitor for this to work. This voltage is supplied either by a battery in the mic or by external phantom power.

Cross-Section of a Typical Condenser Microphone

The Electret Condenser Microphone The electret condenser mic uses a special type of capacitor which has a permanent voltage built in during manufacture. This is somewhat like a permanent magnet, in that it doesn't require any external power for operation. Therefore you don't need to worry about batteries or phantom power.

Other than this difference, you can think of an electret condenser microphone as being the same as a normal condenser.

Technical Notes:

Condenser microphones have a flatter frequency response than dynamics.

A condenser mic works in much the same way as an electrostatic tweeter (although obviously in reverse).