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Theatre Lighting Design: A 7-Part Hub Series -- Part 2: Terminology and Instruments

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Hub Series Table of Contents


First, I want to apologize for getting this out so late. I had planned on getting it out sooner, but have been dealing with some computer issues. With that said, let's move forward.

In part 1, I discussed the basics of the concept and methods of lighting design. In this part, I will be discussing the different types of instruments, their names, their parts, what they do, and how they are often implemented as well as various theatre terms used in the design world. NOTE: There is one term that is seemingly vulgar (uses the “f” word) that will be mentioned herein. It is the actual term used for the part of the instrument. I will not be discussing moving lights, though I may mention/touch on them. I will be focusing on standard theatre lighting only here. As we progress forward throughout the series, you will find that there are only two tools any light tech needs to hang lights: a crescent wrench and sometimes a screwdriver. The crescent wrench is a light tech's best friend.

For some in depth information and incredible detail, check out the "Backstage Handbook". It is a theatre tech's bible. There is an ad for it at the end of this article. As far as I know, every tech and designer (not exaggerating) who went to school for theatre owns a copy. There's a reason for that.

Keep in mind that stage lighting has multiple functions. This following bullet list is copy/pasted from Wikipedia. The only reason I copy/pasted is because it's exactly as I learned it in college. Everything else is in my own words unless otherwise specified.

Functions of Theatre Lighting

The functions of Lighting Design in theatre:

  • Selective Visibility: The simple ability to see what is occurring on stage. Any lighting design will be ineffective if the viewers cannot see the characters, unless this is the explicit intent.
  • Revelation of form: Altering the perception of shapes onstage, particularly three-dimensional stage elements.
  • Focus: Directing the audience's attention to an area of the stage or distracting them from another.
  • Mood: Setting the tone of a scene. Harsh red light has a totally different effect from soft lavender light.
  • Location and time of day: Establishing or altering position in time and space. Blues can suggest nighttime while orange and red can suggest a sunrise or sunset. Use of mechanical filters ("gobos") to project sky scenes, the moon, etc.
  • Projection/stage elements: Lighting may be used to project scenery or to act as scenery onstage.
  • Plot (script): A lighting event may trigger or advance the action onstage.
  • Composition: Lighting may be used to show only the areas of the stage which the designer wants the audience to see, and to "paint a picture"
IMAGE 1: Barn Doors attached to a lighting instrument.

IMAGE 1: Barn Doors attached to a lighting instrument.

IMAGE 2:  C-Clamp.  "Fuck Nut" is facing you.

IMAGE 2: C-Clamp. "Fuck Nut" is facing you.


Terminology that will help you out throughout the rest of the article

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  • Accessory: Anything added to a lighting instrument for its given intended purpose, be it shaping the light, hindering light spill, etc.
  • Area: (Also called “Focus Area”) - This is an arbitrary area or zone on the stage that is decided upon by the lighting designer so that s/he may order each lighting instrument according to stage focus. They are often labeled as Area 1, 2, 3, etc. and typically (though this is designer's choice) run across the stage from down stage right to down stage left, then center right to center left, then up right to up left (depending on size of stage). Also, the areas are typically 8-10 feet in diameter, though this can also vary according to designer, stage space, instruments available.
  • Barn Door: An accessory placed on the end of a lighting instrument to assist with the control of light spread from the instrument. Most commonly placed on Fresnels. It is so named because of its four swinging “doors” that block the light based off their open/closed positions. (See Image 1)
  • Barrel: The part of a lighting instrument casing that holds the lenses. It is most commonly referenced when working with ERSes (see instruments below) due to their ability to be manipulated to twist the light axis for the purpose of shutter cut placement. It is also referenced as “running the barrel” (see below) which alters the focal edge of the light pool.
  • Batten: The overhead, horizontal pipes on which lighting instruments are hung. The most common type run parallel with the stage space (from stage left to stage right) though there are some spaces that also have, in addition, pipes that run downstage to upstage.
  • Beam Area: Each light (especially ERSes) have a beam area and a field area. Some are more evident than others. The beam area is the inner portion of the pool of light that holds a higher intensity than the outer portion. The beam area edge is where the light intensity hits 50% (whereas dead center is 100%).
  • Blocking: The movements of the actors on the stage as set by the director. Often described in terms of upstage, downstage, stage left, and stage right. It defines the actor's space and encompasses any physical movement by the actor.
  • Bottle: A term referencing the oval pattern of a PAR can. The bottle is technically the ceramic connector within the instrument itself. The tech reaches into the back of the instrument and rotates the bottle to change the direction of the oval light pool.
  • Burner Cap: The burner cap is referenced when there is a dark spot on the center of the pool of light. Most often it can be adjusted by turning a thumbscrew on the back end of the light. As the screw is loosened or tightened, the pool of light will either even out or show distinct differences in light intensity. What the screw is doing is moving the actual lamp to the focal point within the reflector to get a more even and more accurate light throw through the lens(es).
  • C-Clamp: The clamp that holds a lighting instrument to the batten. So named because it resembles a “C”. The C-Clamp typically consists of a yoke bolt, a clamp bolt (turned to tighten or loosen the instrument from the batten), and a fuck nut (see below).
  • Channel: An assigned number to which dimmers are allocated in order to organize and group instruments into a design. While the dimmer may be dimmer 1, that dimmer may be assigned to channel 5 (for example) so that when the board operator brings up channel 5, it turns on dimmer 1. (More on this and why this is valuable in part 5).
  • Channel Check: The process of the light board operator and the master electrician of making sure all channels and instruments are functional and still in focus as well as making sure that all color is still holding and not fading or the gels are not burning through (which can happen due to the heat of the light through the plastic gels). The process consists of bringing up each channel one at a time and checking all of the above characteristics. This is done in advance of a performance every night with enough time allowance to replace any blown lamps, replace burned gel, fix dimmers, etc. prior to going into preset and opening house.
  • Circuit: The physical route of a current from source to destination. For example, a circuit starts at the dimmer, then runs through the wire/cable to the raceway, and into the lighting instrument.
  • Color Temperature: Color temperature is measured in Kelvin and denotes the color of the light in question. It is determined by the source light (lamp), any gels in the path of the light, the intensity, and any reflective color of the material being lit. Examples of color temperature:

    Candle: 1900K

    Daylight (clear day): 6500K

    Household Bulb: 2800K

IMAGE 3: Edison Connector

IMAGE 3: Edison Connector

IMAGE 4: Stage Pin Connector

IMAGE 4: Stage Pin Connector

IMAGE 5: Twist Lock Connection

IMAGE 5: Twist Lock Connection

IMAGE 6: Doughnut

IMAGE 6: Doughnut

  • Connectors: Connectors are any termination on a cable (commonly referred to in layman's terms as a plug (male) or outlet (female). Here, we will only talk about the three most common power connectors rather than data. Data's a whole new can of worms.

    Edison: The familiar 3-prong plug with positive blade parallel with the negative blade with a round ground pin below and in the middle.
    (See Image 3)

    Stage Pin: Three in-line round pegs with a split in the middle for adjustment.
    (See Image 4)

    Twist Lock: Similar to Edison, but all are blades in a circular pattern. So called because you plug and twist to lock it in place.
    (See Image 5)

  • Cyc: Short for Cyclorama. It is a backdrop, most commonly white and sometimes concave, and is positioned at the far upstage wall of the stage. The purpose is for scenic depth, fascinating lighting and effects, and is most commonly used to denote a sky (hence the alternative term, “sky cyc”). It is lit with lights specifically designed for a cyc called “cyc lights.” The lights are placed both above and below the cyc, striking the cyc at an extremely shallow angle to spread across as much of the cyc as possible while maintaining light intensity. The blending of light color is amazing and very responsive in this configuration, allowing for a myriad of colors displayed by mixing the primaries (Red, Green, Blue) at varying levels. The cyc is VERY expensive. So.. actors... DON'T TOUCH IT (unless directed to do so for a ripple effect... that's pretty awesome).
  • Degree: The conic angle at which light exits the fore-lens of a lighting instrument. The degrees readily purchasable (through ETC) are 5º, 10º, 19º, 26º, 36º, 50º, 75º, and 90º. The narrower the beam (the lower the degree number), the more intense the light for longer throw distances. Think of the intensity of a laser beam versus the intensity of an omni light such as a household light bulb.
  • Dimmer: The number sequence allocated to each individual circuit in a theatre electrics system. A designer can program the light board for each dimmer ranging from 0% (off) to 100% (full). So with a 500 watt lamp plugged into a dimmer that is brought up to 50%, the lamp output is (ideally) 250W. This allows for better control with maximum granulation and to allow for various effects and mood alteration within the design.
  • Double Purchase: A pulley system that allows the batten to travel twice the distance of the arbor (weight platform). This is often placed in theatres that do not have a full fly-house due to their limited vertical range. Single Purchase is a system with a 1:1 ratio.
  • Doughnut: This is a small square made of either metal or cardboard. It is sized to be placed in the gel frame slots of a lighting instrument. The purpose of the doughnut is to help sharpen the light and reduce 'overthrow' or light scatter. It is most often used in conjunction with a GoBo (template).
    (See Image 6)
  • Downstage: The direction of the stage nearest the audience. So names because primitive stages were raked or angled so the upstage portion (away from the audience) was physically higher in altitude than the downstage portion.
  • Field Area: The field area is the outer circle of light in a light pool. It is the portion that zones from 50% intensity to 10% on the very outer edge. The field area is often more evident in soft focus.
  • Fly: The fly is a system of ropes, cables, and battens that allow the battens to be raised or lowered by pulling on ropes located at the fly rail. It is also a verb as in “fly in” or “fly out”. “Fly in” refers to the fly operator pulling the front rope down to lower the batten toward the stage. “Fly out” refers to the fly operator pulling the back rope to raise the batten toward the grid.
  • Fly Rail: The location of the line sets that control the battens. A fly operator runs the line sets from the fly rail.
  • Focal Length: The distance between the primary and secondary lenses in an ERS.
  • Focus: The act of pointing a light to the appropriate area, shaping the light (shutters, barn doors, etc), and inserting the gel (dropping color). Once the lights are focused, they are ready for the Qing process.
  • Footlights: Lights placed on the downstage edge of the stage to light the actor from below. So named for being at the actor's feet.
  • Fuck Nut: A small bolt on a C-Clamp used to easily rotate the instrument from left to right on the yoke. A tech will loosen the fuck nut, pivot the instrument to the desired yaw, then retighten the fuck nut. It's rumored that it got it's name because it's a knuckle buster if just out of reach (which it usually is). I will let you figure out why that gave it its name.
  • Gel: A filter that goes in the front of the lighting instrument most often to alter the color of the light. However, there are also diffusion gels to diffuse the light to soften the edges as well as color temperature correction gels. In addition, there is what's known as “heat shield” which does exactly that and helps prevent burn through on the color filters. The darker the gel, the more quickly they burn through since the light (which is heat energy) gets absorbed into the gel material.
  • Gel Frame: A square piece of metal with a wide hole in the middle (the size of the instrument's lens). The metal is split on three sides to create a 'sandwich' effect. The tech places the gel within this frame and then places the entire thing in the front end of the light.
  • GoBo: Stands for “Go Between”. It is a pattern template that is placed into the barrel of an ERS. Gobos can be focused for sharp or soft edges and the patterns are only limited by the designer's needs and imagination. Another term used is “template.” Gobos come in six different sizes and must be in the appropriately sized GoBo holder which, in turn, is dictated by the instrument's requirements. The sizes (from largest to smallest) are labeled as A, B, M, G, D, E. The most commonly used size is “B”.
  • Halo: An effect caused, often by worn out shutters or pushing shutters in too far on an oblique angle, whereby the light pool is separated by shadow and then a light artifact appears beyond the shutter cut.
  • Hang: (See “Hang and Focus”) - The process of placing the lighting instrument on its appropriate batten or light tree at its proper position on the pipe and 'prefocusing' to the roughly accurate direction and plugging the light in.
  • Hang and Focus: Often done together (which is why it deserves its own term), hang and focus is the full process of placing the lights on the pipes, tightening them down, plugging them in, and focusing them.
  • House Left: The direction of left while standing in the house facing the stage.
  • House Right: The direction of right while standing in the house facing the stage.
  • In the Round: Defines a theatre space where the stage is surrounded on all sides by the audience.
  • Instrument: Defines the physical entirety of a light. It is the physical body that is hung on a pipe.
  • Inventory: Defines all lighting instruments, cables, gels, and accessories immediately available to the designer.
IMAGE 7: Inverse Square Law

IMAGE 7: Inverse Square Law

  • Inverse Square Law: The inverse square law states that the intensity of the light is inversely proportional to the square of the distance from the source.(See Image 7)
  • Iris: An accessory that is placed into a slot in the barrel (known as the gate) that allows the designer to alter the size of the light pool while maintaining the round shape. Once in place, there is a lever on the Iris that changes the aperture within.
  • Jumper: A piece of extension cable used to span small needs (usually between 1 foot and 5 feet).
  • Knots: Exactly what you think. Knots are very important for safe rigging. Various knots may or may not be mentioned in this series. If so, I will define each one as they come. A great book for useful knots in the theatre is the “Backstage Handbook”, advertised within this article. I recommend anyone interested in theatre design/tech get this book. It's known as the Backstage Bible for a reason.
  • Lamp: The physical light source within a lighting instrument. It is often incorrectly called a “light bulb”. It is not. It is called a lamp. There are various reasons for this I won't get into... just know that it's equivalent to a light bulb.

    Lamps can not be touched. When replacing a lamp, the tech must be very careful to make sure s/he does not touch the glass (technically, it's quartz, not glass). If the lamp is touched, it will blow upon heating up.

  • Light: The actual illumination that emanates from a lighting instrument.
  • Light Plot: More on the light plot with the “paperwork” article. The light plot is a schematic created by the designer and used by the master electrician. The plot is a top down view that denotes light placement, angle, instrument type, target area, color, accessories, dimmer, and channel. It is a scale drafting to show the entirety of the design. When used in conjunction with the channel hookup and the instrument schedule (more on those in the paperwork article), it tells the master electrician exactly what goes where, what its function is, and how to tie everything together.
  • Light Pool: The lighted area on the stage (or set). It is usually round, but can vary with shutter cuts and with type of instrument used.
  • Lighting Tree: A vertical pipe on which instruments are hung. It is often used for side lights and shin lights.
  • Line Set: One set of ropes, pulleys, cables, and a batten connected together and controlled at the fly rail. They are often labeled as “Electric”, “Teaser”, “Main Drape”, etc. Each label refers to the fly's intended function, though they are sometimes interchangeable.
  • Lux/Foot Candles: A measurement of light intensity.
  • Married: Tying two battens together, often for the purpose of hanging lights on a non-electric batten so that they can cross plug into the proper raceway. Marrying battens requires two fly operators to fly the battens in and out together to avoid damage.
  • Ohm's Law: Amps equals Volts divided by Resistance:

    A=V/R --> 20=120/R --> R=6Ω

  • Patching the Board: The process of assigning dimmers to channels. Most boards default at 1:1 and from there, the designer can assign dimmers to channels.
  • Power Law: (Sometimes called the West Virginia Law) – Watts equals Volts times Amps

    W=VA – W=110*5 – 550W

  • Proscenium: The most familiar stage set up that involves the audience on one side of the stage where the actors are viewed through the Proscenium arch as a type of “moving picture”.
  • Proscenium Arch: The physical archway that frames in a proscenium stage.
  • Raceway: A row of circuit outputs from multiple dimmers placed in a single housing usually along a batten or house pipe.
  • Rigging: The process of securing lighting instruments (among other theatre pieces) to the pipes to ensure safety and stability.
  • Run the Barrel: The process of turning a knob on the barrel of a lighting instrument (ERS specifically) and then moving the lenses inside the barrel by using the knob forward or backward. This allows the technician to manipulate the light pool between sharp focus and soft focus. If you run the barrel out (toward the frond of the instrument), the light focuses inward, making a smaller light pool, but also softening the edge. If you run the barrel in (toward the back of the lighting instrument), the light focuses outward, making a larger light pool and also softening the edge. In the middle is sharp focus (which is the location of the barrel when the degree rating is issued to the light).
  • Scrim: A drape that when lit on an oblique angle from the front, appears like a solid wall, hiding action behind. When there is light behind the drape, the appearance of the scrim disappears as though it dissolved away, allowing action behind it to be seen. Lighting Designers love scrims. But they're also VERY expensive. So... actors... DON'T TOUCH IT!
  • Sharp Focus: Sometimes referred to as “blue edge” due to the thin blue line along the circumference of the light pool, sharp focus is the setting in the barrel that forms a very sharp/hard edge on the light pool with a distinct inside and outside to the pool, itself.
  • Shutter: Four blades found within an ERS. The shutters are manipulated to change the shape of the light pool as well as its size. This allows the designer to display a very specific lighted space.
  • Shutter Cut: The effect of the movement of a shutter inside an ERS. The shutters affect the opposite side of the light pool. So if you push in the top shutter, it will be reflected in the bottom side of the light pool which is often referenced as a bottom cut.
  • Soft Focus: Upon running the barrel in or out of focus (sharp), the edges of the light pool begin to haze or 'soften', reducing the apparent edges of the light pool and allowing the light to dissolve away with a much less 'harsh' effect. This setting allows the designer to blend two or more light pools into each other while eliminating the effect on the actor as s/he walks from one area to another. When using ERSes for stage washes, this is the setting used to allow even and consistent light across the stage.
  • Special: A specific and defined area with a specific and defined purpose to which a lighting instrument is focused. It is any lighting focus that is outside any 'wash' lighting. Specials are often used for mood or to direct audience focus and attention to a given location. When an actor gets a special, they're usually thrilled because it means the lighting designer is focusing on them at a given moment (though you can have multiple specials happening at once).
  • Spike: A blonde-headed sarcastic British vampire who resides in Su-- oh. Wait. Wrong article.

    Sorry about that. Spike in this sense is a process of noting, on the stage, where specific set pieces go or where actors are to stand during specific times throughout the performance. The stage is “spiked” so that the stagehands are consistent with their placement of the set pieces each night and so that actor's are consistent with their stage location when specials are required for them. While we now use color coded tape for this process today, the term comes from when the stages were raked (see upstage/downstage) and actual physical spikes were used to hold the set pieces in place so they didn't slide down into the audience.

  • Stage Left: The direction of “left” as seen by the actor facing the audience. Even if the actor is on stage facing the upstage wall, the direction of stage left does not change.
  • Stage Right: The direction of “right” as seen by the actor facing the audience. Even if the actor is on stage facing the upstage wall, the direction of stage right does not change.
  • Thrust: A stage that is surrounded by the audience on three sides.
IMAGE 8: Top Hat

IMAGE 8: Top Hat

IMAGE 9: Lighting Parts. Yoke labeled.

IMAGE 9: Lighting Parts. Yoke labeled.

  • Top Hat: (Also known as a “snoot”) – This is an accessory that is placed in the front end of the instrument (same place as gels, barn doors, etc.). Its function is to allow for the full size light pool while shielding the audience's eyes from the light source (so most often used for back light). Another function (and one for what I most often use) is to reduce halo and light spill, often hitting the proscenium or set pieces intended to remain unlit. While the Top Hat gets its name from the fact that it looks like a top hat (I may or may not have worn them as such while in college), there are also “half hats” where the cylinder is cut in half down the long axis.
    (See Image 8)
  • Two-fer: This is similar to a jumper, but has one male end and two female ends. The purpose is to allow two instruments to plug into one circuit. When using a 2-fer, be aware of the power law. A 2-fer is most often used when there aren't enough circuits for the instruments. The instruments plugged into a circuit using a 2-fer are those that don't require as much control granularity and will always be brought up together; typically a downlight pair.
  • Upstage: The direction of the stage away from the audience (see “downstage” for etymology).
  • USITT: United States Institute for Theatre Technology. USITT is the organization that sets the standards for theatre lighting such as symbols, color coding, etc.
  • Wash: To flood the stage with even and consistent light. There are various wash styles and often combined into a “full wash”. Washes can be cool, warm, back, down, front, or any combination of the above.
  • Yoke: The U-Shaped bracket portion of a lighting instrument that allows the instrument to be pivoted vertically.
    (See Image 9)
IMAGE 10:  Cyc Lights

IMAGE 10: Cyc Lights


Cyc Lights:

These vary a bit but typically have a half cylindrical reflector. Their purpose is to flood the cyc with light. The most common colors used in cyc lighting are the primaries. Some cyc lights allow for 4 colors, in which case, the 4th color is commonly yellow or a special color depending on intent. Cyc lights are designed to flood the cyc with absolutely smooth and even light, but must be carefully designed at the appropriate angle to and distance from the cyc.

IMAGE 11: ERS (Specifically a Source 4 by ETC)

IMAGE 11: ERS (Specifically a Source 4 by ETC)


ERS stands for “Ellipsoidal Reflector Spot”. It is probably the most commonly used light in theatre today due to its versatility. Many designers like to use the ERS for washes because of their versatility and for the amount of control they allow the designer. They offer specific light pool sizes, shutters, and various focal settings (soft to sharp to soft). ERSes are denoted by degree or as 4.5 by 6, 6 by 9, 6 by 12, 6 by 16, etc. The numbers indicate: diameter of lens by focal length. ERSes can focus light so well, that you can literally light a cigarette off the beam of light. I often use this demonstration during workshops to show students how hot the light can get.

Fog Machines:

I'm not going to get into specifics of fog machines, but know that they are the responsibility of the lighting designer. There are different types. There are “cold fog” which is typically a dry ice set up that keeps the fog low to the stage, all the way up to 'hazers' which distribute the fog evenly. When dealing with fog, the designer needs to know EVERYTHING about the theatre... especially airflow due to air conditioning/heating, ventilation, etc. By not being aware of this, it can destroy a design in seconds.

IMAGE 12: A Fresnel lens.

IMAGE 12: A Fresnel lens.


The Fresnel is named for the type of lens involved. It is what is known as a “step lens” and was developed for light houses before being adapted to the theatre. You can identify a Fresnel by this attribute alone. If you see a lighting instrument that seems to have concentric circles on the lens, that is a Fresnel. The Fresnel instrument can focus (always soft focus) from spot to flood by sliding the lamp toward or away from the reflector or by turning a knob (which performs the same action). The size of the Fresnel is dictated by the diameter of the lens: 6 inch, 8 inch, 12 inch, etc. The reflector in a Fresnel is half-spherical. They are commonly used for down light.

Light Board:

The light board, while not an instrument, is the control console. This is where the magic really begins to take place. There are so many types of light boards, I won't get into it here. Some are fully programmable, including moving lights and audio... others are simple slider boards that can not be programmed. Interestingly, the more complex looking the board, typically the easier it is to operate. Go figure.



IMAGE 14: Zoom instrument

IMAGE 14: Zoom instrument

PAR Can:

“PAR” stands for Parabolic Aluminized Reflector and describes exactly what the instrument is. This instrument is usually used for stage washes. The output light pool is oval in shape and can be manipulated by turning the bottle. This manipulates the long axis of the oval on a 360º rotation. The lamp and lens of a PAR can are an enclosed unit. The lenses come in Very Narrow, Narrow, Medium, Wide, and Very Wide. There is a grid pattern on the lens, itself, to cast the pattern desired. The instrument comes in various sizes ranging from PAR 16s (very small – desk size) to PAR 64s (used for large washes and large stage spaces). The lamps resemble car headlights (and are actually used for car headlights). The great thing about the PAR can is that they are the workhorse of the theatre and are water resistant (for the most part). They are also what you usually see at rock concerts and in bars because they are minimal in design and cheap in cost. They consist of a metal shell and the lamp housing.


Technically, a “zoom” is an ERS, but very adjustable. The zoom allows the designer to maintain a sharp edge of the light pool while altering the degree angle by focusing the lenses by sliding them forward or backward. Once the focus is established, it can then be softened by moving a single slider.


LED is just what you expect (Light Emitting Diode). In theatre lighting it is any instrument type that uses LEDs instead of the typical respective lamp type. An instrument using LEDs is prefixed as such. For example: LED PAR, LED Fresnel, LED Cyc, etc.

In Closing

There are many more instruments that could be on this list, but I am focusing on those most commonly used. The way theatre is evolving, intelligent lighting could very well be on this list but I am already at almost 5000 words and to include them wouldn't add anything to the article (and would actually add about 3 more parts to the series).

I know there is some stuff I left out; some intentionally, some I may have forgotten to include. Please don't hesitate to comment on that or ask questions in the comments. Due to the overlap of sections throughout the series, some I may be waiting to touch on until the appropriate part.



Joe Poniatowskis from Mid-Michigan on November 15, 2013:

What an awesome series for anyone interested in theater production, either professionally or for community theater.

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