The Cranky Old Gnome

Now that I am going to be blogging quite a bit more about my real life and what I do for a living, I will be using terms that will probably be unfamiliar to most of you.  Even if on the off chance some of you do happen to work in the same industry as I do, we may refer to things by different names.  So to forestall any confusion I’ve decided to provide a glossary of terms that can be referred to any time I am discussing this particular topic. I’ll do my best to make it comprehensive (i.e. warning it’s going to be long), and add any new terms I happen to use in future posts down the road.  If you don’t understand something, by all means, leave a comment and ask me and I’ll do my best to clear it up.  I’ve tried to divide it into sections to help give a little context.  Hopefully they make sense (more than just in my own head).  Also, I should note that some of these definitions are modified from definitions given on this website.

Finally, it’s not my intent to make you all professionals overnight just by reading this, but I do want to make sure that I am describing things clearly and in a way that allows you to visualize what I am talking about.  This is why I want you to tell me if something doesn’t make sense because I want to make sure it’s clear.

–Crew:

Assistant Lighting Designer: The ALD typically has the authority to make decisions regarding the light plot in the absence of the Lighting Designer.  Very often the ALD will run a focus and be on sight during load in to answer questions.  Sometimes referred to as the Associate Lighting Designer.

Board Operator: The board op runs the lighting console during a performance.  Sometimes (but not always) the board op is also the programmer.  Depending on the type of production, they board op may take their cues based on instructions from the stage manager or lighting designer, or they may take their own cues.

Electrician: A stagehand that specializes in the electrics department.  Various duties of an electrician include: Hanging light fixtures, focusing, troubleshooting and maintaining electrical equipment, patching, programming/running a lighting console, and swapping gels during a scene change.  The “Master” Electrician or “Production” Electrician is the chief of the electrics crew and makes all the decisions regarding the installation and maintenance of the light plot.

Follow spot Operator: Operates one of the follow spots during rehearsals and performances.  Usually (but not always) part of the electrics crew as an electrician as well.  They usually take their cues on their own or from the LD or ALD in live music events, or from a stage manager during a theater/dance piece.

Lighting Designer: The LD is in charge of making all artistic decisions regarding the installation and execution of the lighting design viz a vie the light plot.  Sometimes the LD also serves as the Master/Production Electrician, and/or the Programmer/Board Op.  If the LD is not directly operating the board, then they will instruct the programmer as to what they want the looks to be, and the programmer will input the commands into the console.

Lighting Director: This type of LD is sort of a hybrid of the designer and the master electrician.  Typically the lighting director position is filled when there is a production designer.  The production designer will make all the overall, big picture design decisions, and the lighting director will make the implementation and installation decisions.

Production Designer: Often found more in live music events, the production designer is in charge of the design aspects of the production as a whole; lighting, scenery, costumes, sound, and video.

Programmer: The programmer parks them self in front of the lighting console and inputs commands to control the lighting rig based on the instructions of the LD.  Very often the programmer is also the board op during performances.

Stage Hand: A generic term for a person that works on one of the various backstage crews.  Typically refers to one of the general crew members and not a crew chief.

Stage Manager: A stage manager is in charge of interfacing with the director and actors; running rehearsals; coordinating with the design staff; and running/calling the show during rehearsals and performances.  The stage manager and her assistants are the most important, and least appreciated people on the crew.  Period.

–Equipment (Cable, tools, etc)

Adapter: Any cable that has different connectors on either end; used to adapt one type of connection to another. E.g. A M/Ed is a male Edison to female stage pin adapter (a F/Ed would be the opposite).

Aircraft Cable: Stainless steel stranded metal cable (in various diameters) used for rigging.  Very strong, and fairly light.

Ballast:A device intended to limit the amount of current in an electrical circuit.  In the entertainment world you will usually find ballasts with follow spots and fluorescent lights.

Barn Door: A special device that can be placed on the end of a lighting fixture (in front of the lens).  A barn door has four ‘fins’ that can be adjusted to block a portion of the light coming out of the unit.

Batten: A movable (up and down) pipe that typically extends the length of the stage from left to right, from which lights, scenery, and drapes are hung.

Blackwrap: A type of thick black tinfoil that is used to mask stray light coming out of cracks and holes in lighting fixtures.

Boom: A vertical pipe attached to a base on which lighting fixtures are hung.  Booms are typically placed off stage left/right, and the lights are hung on them using side arms.

Boom Base: A large, heavy, circular piece of iron used to anchor boom pipe.

Boomerang: A removable part of a followspot that holds different colors of gel.  Placed between the lamp and the lens.  Typically holds 6 colors.

Break In/Out: A type of multi-cable connector, that breaks the mult into 6 to 12 individual circuits.  A break in provides connectors while a break out provides female connectors.

C-Clamp: A steel clamp that attaches a lighting fixture to a pipe.

C-wrench: An adjustable crescent wrench used by electricians to hang, focus, and maintain lighting fixtures.  Sometimes in lieu of a c-wrench they will use a speed wrench which is a ratchet specifically designed to fit the bolts of most lighting fixtures.

Cable Lengths: Although there are many types of cable, they all come in fairly uniform lengths.  In the US the standard lengths are 5′, 10′, 15′, 25′, 50′, 75′, 100′, 125′, 150′, 200′, 250′.

Caltwalk: An elevated walkway that extends over the house or stage, allowing access to lighting fixtures and cabling, as well as audio and video equipment.

Camlock: A locking single contact connector typically used on feeder cable and power distros/supplies.

Chain Hoist (motors): A lifting device comprised of an electric motor and gear/chain drive system. Chain hoists are commonly used to lift portable trusses into place for touring concerts and shows.

Circuit Tester: A devise with a male stage pin connection used to test the wiring of a circuit.  Also known as a Gam Check (brand name).  The other side of a Gam Check has a female stage pin connection and is used to check if a lamp is working.

Color Extender: A metal tube that is attached on the end of a lighting fixture (after the lens) to extend the distance between the light and the color (gel).  The idea is to move the gel further away from the hot spot of the lamp so that the color (especially very saturated colors like deep blue or deep red) will last longer.

Com System: A communication system consisting of a headset and belt pack.  This is the primary method of communication between the stage hands during a rehearsal/performance.

Company Switch: A disconnect used to hook all of the visiting companies electrical equipment into the main power box of a venue.  The company switch distro box has it’s on on/off switch that can be controlled by the visiting company.

Cyc (Cyclorama): A smooth backdrop (typically white) at the back of the stage, often used to create sky effects, but is also sometimes used as a projection surface.

Data Cable (DMX Cable): A special type of cable used to connect automated lighting together, and to send data from a lighting console to a dimmer rack or automated lighting system.

Dimmer: An electrical device that provides power for a lighting fixture and is used to control its intensity.  Multiple dimmers packed together in one piece of housing is called a dimmer rack.

DMX 512: A type of data protocol used to control lighting systems.

Duvetyne: A type of heavy black cloth used as masking.

Edison Cable: A type of cable with an Edison connection.  An Edison connection is a typical US power cable.  It’s the same as any household device you might own light a computer or a television.  It has two prongs and a ground.

Feeder Cable: Freaking heavy-ass cable that is used to supply power to a dimmer rack.  Feeder is heavy gauge cable usually with Camlock connectors that carries hundreds of Amps.  There are typically 5 separate cables in a set of feeder.  Three ‘hot’ cables, one ‘neutral, and one ‘ground’.  Feeder is very dangerous and should only be handled by experienced and trained electricians.  For the love of God if you don’t know what you are doing DO NOT TOUCH FEEDER CABLE!

Fogger/Hazer: An atmospheric effect used to fill the stage with haze or fog of various thickness.  Fog/haze is very effective is creating ‘beamage’ in the air where the beams of light can be seen punching through the fog/haze.

Gaff Tape: The stagehands version of duct tape.  Gaff tape is a fabric tape that comes in many colors and sizes, although the most common form is in 2″ black.  Gaff tape can be used to connect anything, and is preferable to duct tape because it doesn’t leave behind a sticky residue (if it’s good quality anyway).  Duct tape is for more permanent fixes, and isn’t really used often in the entertainment world since everything is temporary.  Gaff tape is the way to go because it holds well, is machine washable (I’ve fixed many tears in my clothes with it), is black (so it doesn’t stand out), and doesn’t leave a sticky mess.  Remember, when in doubt, Gaff it out!

Gel: A term used to describe expendable color filters used in stage lighting.  Originally made of thin sheets of dyed gelatin, color filters are now made from polymer plastics.  For a while there was a big push to get everyone to start calling it ‘color media’ but it never really caught on, and everyone still calls it ‘gel’.  Gel comes in ’sheets’ and is then broken up into ‘cuts’ which get placed into frames (typically metal and square), and finally placed on the front of a lighting fixture, just past the lens.

Genie Lift: A brand name for a personal lift.  It’s basically a bucket attached to a vertically extend-able arm.  This is how we are able to get to lights high up in the air from the ground when there is no catwalk.

Iris: A device commonly used in an ERS or follow spot to reduce the apparent diameter of the beam of light. Many automated fixtures also employ a motor controlled iris which can be used to remotely adjust the beam diameter.

Jumper: A short cable that is used to ‘jump’ a small distance from one cable to another. E.g. if I have a cable running along a pipe and it comes up 3 ft short of the unit, I would use a 5 ft jumper to make the connection.  Typically anything shorter than 25′ is considered a jumper.  After that it’s just a really long connection.  Although, there are those crappy times when all you need is to get 2 more feet but all you have left is a 50′ cable.  I hate that.

Light Board (Control Console/Desk): A specialized computer designed to control lighting fixtures (and any other type of electronic equipment that has been fitted with the proper interface).  These boards can store cues that can be recalled later.

RFU: Remote Focus Unit.  This is the brand name used by ETC, but can refer to any device that allows you to remotely control the functions of a light board.

Safety Cable: A short steel cable used to attach lighting fixtures to pipe as an extra precaution in case the c-clamp fails.

Scrim: One of many types of woven gauze-like scenic materials. A scrim will appear as opaque when lit primarily from in front, or can become transparent when objects are lit behind it. It’s like magic!

Scroller: A color device attached to the end of a lighting fixture.  A scroller has a roll of gel that can be adjusted from the left scroll to the right scroll to change which color is in front of the lens.  Some scrollers have one roll of gel and some have two.

Shutter: A thin fin of metal that is part of an ERS light, between the lamp and the lense, that is used to block the transmission of light.  The resulting effect of the shutters position on the beam of light is called a shutter cut.  Cuts are often made to eliminate unwanted parts of the field of light that may hit the scenery or audience.

Side Arm: A small pipe that is used to attach a lighting instrument to a vertical pipe.

Spanset: A piece of webbing used in rigging.

Stage Pin Cable: The standard connector in US theater.  It has 3 pins like an Edison connector does, but they are placed in a straight line, rather than two over one.  I recommend doing an internet search because my descriptive powers seem to be failing me here.

Top Hat: A long metal tube attached to the end of an ERS light used to reduce the flare produced by a lamp.  Also comes in half hat (or eye lash) versions, which only cuts the flare on one side of the light (e.g. the down stage side that shines towards the audience).

Truss: A steel or (more commonly) aluminum structure used for rigging (hanging) lights, scenery, drapes, etc.  Most of the truss I encounter comes in 12″ x 12″ or 20.5″ x 20.5″ versions and comes in varying lengths, and is then bolted together to form longer spans.  Often times with the larger versions of truss, wood planking is placed on top of it and it is used as a catwalk.

Twist Lock: Another type of cable connector, with blades instead of pins.  Most automated fixtures use some version of the twist lock cable (L6-20 usually).

Twofer: An electrical connection that allows you to connect two lighting instruments into one cable (or circuit).  Also known as ganging.  Depending on the number of watts used by each lamp, and the capacity of the cable/circuit/dimmer multiple lights can be ganged into one circuit (twofer, three-fer, four-fer, etc).

–Electrical/Lighting Terms:

Alternating Current (AC): I refer you to the wikipedia article.  It’s way more thorough than I want to be.

Address: A number used to identify a moving light according to its DMX attributes; allows a console to communicate with the light.  If a fixture has multiple attributes then the address number given is the starting address, and the light will take up a range of addresses.  So, if a light has 5 attributes (pan, fine pan, tilt, fine tilt, intensity) it would take up address numbers 1-5.  If you had a set of 6 of these types of lights then the starting addresses would be 1, 6, 11, 16, 21, 26.  And the next available address would be 31.

Amps: A unit of measurement describing the amount of current flowing through an electrical circuit.

Attribute: An attribute is a channel of control, such as intensity, or shutter.  Conventional units have only one attribute: intensity.  Automated units can have many, many attributes such as: intensity, pan, fine pan, tilt, fine tilt, color change, iris, zoom, gobo, rotating gobo, and so on.

Black Out: Turning off all the lights on the stage.  In a normal blackout, a small amount of blue light is left on so that performers and technicians can still see onstage enough so that they can move about safely.  In a “dead” blackout, all light sources (except for exit signs and other emergency lights) are removed.  Blackouts can be “hard” (fast/instant) or “soft” (long/slow).

Bump: Lighting: Rapidly increasing or decreasing a unit’s intensity to full or to zero.  Typically this intensity change only lasts briefly and then is returned to its previous level.  Rigging: Tapping the up/down control button to slightly raise or lower the height of a hanging object by a very small amount.

Channel: A number used to identify and control a lighting fixture.  This is the number is the first number in the chain of numbers used to identify a light.  That chain is Channel>Dimmer>Circuit>Unit.  When using automated lights, the channel number is known as the Fixture number (not to be confused with the address).

Channel Check: A channel check is when an electrician goes through every light in the rig to make sure that it is working and is still focused properly.  Also called a flash through, as the intensity of every light is ‘flashed’.  Channel check also includes checking each of an automated lights’ attributes, verifying that all the practicals work, and checking that anything else that the lighting console controls is working (e.g. hazers, fans, work lights, coffee makers, etc).

Circuit: A number used to identify the cable that connects a lighting fixture to a dimmer.  This is the third number in the chain of numbers to identify a light.  That chain is Channel>Dimmer>Circuit>Unit.  If the circuit runs through a multi-caple it also has a letter attached to it.  E.g. The D mult breaks into 6 circuits, so a unit plugged into the 4th circuit would be numbed D-4.

Cross Fade: A smooth transition from one lighting look to another.

Cue: A set of data containing information about the attributes of each light that can be recalled later.  For example Cue 1 might have channels 1-5 at 50% intensity, and cue 2 might bring channels 1-3 to 0% and 4-5 to 100% intensity.

Direct Current (DC): I refer you to the wikipedia article.  It’s way more thorough than I want to be.

DMX 512: This is how the channel numbers communicate with the dimmer numbers.  The lighting console sends data down the dmx cable to the dimmer rack, and then the dimmers turn on or off based on the info sent.  Or, if the console is controlling a moving light the cable can connect directly to the lighting fixtures.  In a dmx “universe” only 512 different channels (or attributes) can be controlled.  Conventional lights only take 1 channel of DMX, so you can control 512 conventional lights in a universe.  Automated lights can have anywhere from 3 to 50+ attributes so you may only get as little as 10 lights in a universe, depending on how complicated the unit is.

Effect: A chase, fade, strobe, ballyhoo, figure 8, or any other type of movement or intensity change preprogrammed that effects a light or lights in the rig.

Flagging: An electrician ‘flags’ a light by waving their wand in front the units’ lens, causing the field of light to flicker.  This allows the designer standing on the deck to distinguish that particular light amongst others that might be up at the same time, and make any necessary adjustments to its focus.

Flood: To ‘flood’ a light means to spread out the field of light as far as possible.  This is done by moving the position of the lamp closer to the lens.

Focus: To change the way a lighting fixture is pointing.  During a focus session, electricians will be placed at various points throughout the venue where they can access the lighting rig.  The lighting designer then stands at various points on the stage and set and tells the electricians where to point the lights.

Hookup: A document that lists all the lights in the rig and contains a series of helpful information about each unit (channel/dimmer/circuit/unit number, position, purpose, color, unit type).  There are a number of types of hookups, the most common being the channel hookup (this is used for channel check).  Other hookups include: Dimmer, circuit, system, universe, position.

Kill it: Take the intensity of the light to zero.  Synonymous with “save it”, “take it out”, “next” (implies take the current one to zero, go to the next channel in numeric order and bring it to full).  Personally, I use “next” during channel check when I’m going from channel to channel, “save it” during focus where I’m bouncing around from light to light, and “kill it” when I really need that light to go out right this second and if you don’t take it out right now we’re gonna have serious problems.

Lamp: We call them lamps not light bulbs.  Remember that.  The quickest way to sound like a giant noob is to ask for a light bulb instead of a lamp.  So what normal people call light bulbs we call lamps, and want normal people call lamps we call fixtures.

Load In/Out: Bringing equipment, scenery, etc off a truck and into a theater, then installing and troubleshooting everything is load in.  Taking everything down and then packing it all up and out of the theater is called load out.

Magic Sheet: A little cheat sheet that designers use as a reference to easily identify lighting systems in the rig.

Multi-cable: A multi-core cable that allows multiple circuits to run through one line of cable.  Multi-cable allows you to run 6 to 12 cables in the space of one.  Then all you have to do is attach a break in/out at either end.  (Brand names: Socapex, Pyle National)

Ohms: To wikipedia once again!

Pan: To move a light (manually or automatically) left/right.

Patch: A hard patch is when you connect circuits to dimmers.  A soft patch is when you assign dimmer numbers to channel numbers.

Plot: A ground plan that gives an detailed picture of all the lighting fixtures in the rig.  It shows a ground plan of the venue, and then a plan of all the lighting positions on top of that, and then all the lighting fixtures on top of that.  The plot also includes channel numbers, gel color numbers, unit numbers, and sometimes also circuit and dimmer numbers.  Depending on how complicated the plot is, a section view and front elevation also needs to be provided.  A ground plan is an overhead view, a section is a side view, and a front elevation is a view from the front.

Programming: Putting information about each lighting look (or cue) into the lighting console.  Programming also includes setting up effects and moving light looks.

Rep Plot: Most venues have one plot that is the standard that they have up all the time.  This is called the rep (repertory) plot.  The rep plot is designed to give the maximum amount of flexibility, but may also end up looking very generic.

Rig: Noun: A term used to refer to all the lighting fixtures in the plot.  Verb: The act of hanging an object.

Spot: To ’spot’ a light means to tighten the field of light in as much as possible.  This is done by moving the position of the lamp further away from the lens.

Tie in: The process of connecting dimmer rack feeder cable to a company switch or power supply.

Tilt: To move a light (manually or automatically) up/down.

Voltage: Wikipedia again?

Wattage: Yes, that’s right. Again.

Zoom: Zooming a light in and out will change the diameter of the field of light.  As you zoom in the diameter gets smaller and as you zoom out the diameter increases in size.

–Stage Directions, Venue Terms, & Lighting Positions/Uses:

Back Light: Light that is placed behind the performers and shines on their backs providing a silhouette effect.

Backstage: All the areas of the venue to the left, right, and behind the stage.  Backstage can refer to offstage left and right, but usually refers to the parts of the venue that isn’t in the immediate vicinity of the stage.  The backstage areas contains: dressing rooms, cast/crew bathrooms, green room, shop, loading dock, dimmer room, and some administrative offices.

Balcony Rail: A lighting position–a pipe hung along the edge of the Balcony

Boom: A vertical lighting position consisting of a vertical pipe attached to a heavy steel base.  Typically placed off stage left or right for side light.

Box Boom: A vertical lighting position, typically permanently attached to the wall down stage of the proscenium.

Deck: The stage floor, including the offstage areas.

Downlight: Light that shines straight down; creates deep shadows on faces and cool highlights.  Helpful for shadow fill.

Down Stage: The down stage area is everything downstage of center.  To move downstage is to move away from the back of the stage towards the proscenium.

Green Room: A room backstage typically used as a waiting room/lounge that performers can wait in, in costume, while they wait for their cue to go onstage.  The origin of the term is lost to the annals of history, but that certainly hasn’t stopped those in the theater from coming up with their own imaginative origins of the term.  Do an internet search sometime, you’ll find some amusing stories.

House: The area of the venue that the audience sits in.

House Left: The left side of the house, if you were standing in the house looking at the stage.

House Right: The right side of the house, if you were standing in the house looking at the stage.

Fill Light: Soft light used to ‘fill in’ and provide bits of highlight.  Similar to shadow fill.

Floor Mount/Plate: A lighting fixture that is attached to a small metal or wood plate and placed on the floor.

Fly Rail: The area offstage left or right where the fly system is operated.

Front Light: Light that is placed in from of the performers.

Front of House (FOH): A term used to refer to generically to the house and all the services involved therein.  As a term used to refer to the place where the lighting and sound consoles are placed, as well as (sometimes) the stage manager.  Finally, any lighting positions that are on the audience side of the proscenium (or downstage edge of the stage if there is not proscenium) is called the FOH position.

Head Highs: Lights placed on a boom at head height (usually 5′-8′).  Any lights placed over 8′ are typically called Double Head Highs.

Mids: Lights placed on a boom at waist height (usually 3′-5′).

On/Off Stage: On stage includes any area of the stage that is utilized during the performance.  Any place ‘onstage’ is considered to be in play and if a performer is standing there they are part of the action, and not just waiting offstage to enter.  Off stage is considered the areas of the stage off to the left and to the right that is masked so that the audience can’t see it.  (note: sometimes you can’t really mask the off stage areas, or there just isn’t really enough space to have an off stage area and the performers just have to stand at the very edges of the stage.  In these situations, the unmasked ‘offstage’ areas are kept as clear as possible, and performers only enter the areas just before they need to enter ‘onstage’.  While in these offstage areas they are expected to move and act in such a way that it indicates to the audience that they are not a part of the current action onstage).

Shadow Fill: Light used to fill in and highlight the ’shadows’.  This is a tricky concept.  Lit shadows?  Let me give you an example.  If you have a person on stage and you shine a soft dark blue light on their right side, and a strong bright yellow on their left, then the left side of the performer will be bright and highlighted yellow, and the right side will look dark and in shadow, but if you look closer you will notice little bits of blue color.

Shins: Lights placed on a boom at shin height (usually 0′-3′).  Often called shin busters because if you aren’t careful, you can walk right into it and slam the heck out of your shins.  Performers, especially dancers, are especially prone to walking right into these lights.

Side Light: Light placed off to either side of the stage used to create interesting highlighting effects from the side.  This type of lighting is used heavily in dance.  Lights hung on a boom are typically referred to as side light.

Spike (mark): A spike mark is a mark placed on the stage or a piece of scenery, made from a small piece of spike tape (small colored gaff tape).  A spike mark is used to indicate placement for scenery or audio equipment, or where a performer should stand during a particular part of the show.

Stage Directions: Stage directions are tricky though, and you have to remember that the orientation and directions are based on the perspective of the performer.  So if you were standing on the stage looking out towards the house, stage left would be on your left hand side.  But if you were sitting in the house looking at the stage, stage left would be on your right hand side.

Stage Left: The area of the stage left of center.  To move stage left is to move from any point on the stage toward the left side of the stage.

Stage Right: The area of the stage right of center.  To move stage right is to move from any point on the stage toward the right side of the stage.

Strike: To remove an object from the stage.  Also, a term synonymous to load-out, where the scenery, lighting, and audio elements are ’struck’ or removed from the stage, packed up, and stored away or removed from the venue.

Uplight: Lights placed on (or in) the deck that shine straight up at a performer, scenic object or drop.

Upstage: The area of the stage up of center.  To move upstage is to move from any point on stage towards the back of the stage, away from the proscenium.

Venue: A term that refers to the entire building or area where a performance is going to take place.  This includes the house, stage, backstage, etc.

–Types of lighting fixtures:

ACL (Aircraft Landing Light): A 28 volt very narrow PAR unit.  Typically used in PAR 64 versions (and sometimes in PAR 48 versions) and wired in series to bring the voltage up close to the standard 120 volts.  ACLs are often used as punch lights, and for creating beam effects in the air.  This lamp was originally used on airplanes to help illuminate the runway, but was adapted for theatrical use.

Automated Fixture/Lighting (also Intelligent Lighting): Any type of fixture that has part of it’s functionality electronically or mechanically automated.  Typical automatons include: Power (on/off), movement (pan/tilt), dimming/brightness, shutter, color change, gobo change, iris, strobe, and zoom.  Automated fixtures come in two main types: moving mirror (where the unit itself is stationary and only a small mirror moves), and moving yolk (where the entire unit (placed on a base) moves).  Automated lighting provides a great deal of flexibility but also adds a high level of complexity, and requires specially trained personal to maintain and operate.

Conventional Fixture: A catch-all term that refers to any lighting fixture that has no automated attributes.  Basically all a conventional fixture does is turn on and off.

ERS: Ellipsoidal Reflector Spot (also known as an ellipsoidal, or by various brand names like ‘Leko’ (Strand Lighting) or a ‘Source 4′ (ETC) ), named for the ellipsoidal reflector placed at the back of the light, used to capture and reflect the light through a barrel that contains a lens (or lens train).  The ERS is one of the most common and frequently used lighting fixtures in the entertainment industry.  The common characteristics of the ERS include:

• An ellipsoidal reflector
• A lens or lens train
• An adjustable barrel, allowing the designer to change the focus (softness) of the beam of light by changing the distance between the lens and the lamp.
• Some ERS fixtures also have a zoom feature that allows the designer to change the size of the pool of light cast.
• Two plano-convex lenses in the barrel which face the convex sides together.  The distance between these lenses plus the lens size determines the field angle, or how wide the light output is.
• A set of brackets placed at the end of the barrel in which gel can be inserted.  These brackets can also house barndoors, scrollers, color extenders, top hats, etc
• A series of adjustable shutters (metal fins) for the shaping and narrowing of the beam of light.  e.g. The beam of light is (usually) round and by using the four shutters, the beam of light can be shaped into a square.
• An iris (or iris slight), allowing for the narrowing of the beam of light in a circle.
• A slot between the lens and the lamp for the insertion of gobos.
• A rear loaded lamp mounted either axially (in line with the rest of the fixture) or radially (at a 45° or 90° angle to the rest of the fixture).

The size of the light coming out from an ERS is defined by it’s field angle.  The technical definition of field angle is the angle of the beam of light where it reaches 10% of the intensity of the center of the beam.  What that actually means is it’s the size of the beam of light that comes out of the fixture, measured in angles.  For example, a 36° fixture would side out a beam of light that, if one edge of the beam was flat on the ground, the rest of the beam would arch out in a 36° swath.  Newer ERS fixtures are named by the number of their field angle (5°, 10° 19°, 26°, 36°, 50° 75°, 90°).

Older fixtures (and still some fixtures made by Altman) are defined by the width of the lens x the focal length of the instrument.  For example, a fixture called a 6×9 (6 by 9) would have a 6″ diameter lens and a focal length of 9″, which gives a field angle of roughly 37°.

As the field angle narrows the light can be used further away from the stage.  Or another way of thinking is the further away the lighting position is from the stage the smaller the field angle that will be needed.  Typically the ERS is used as a hard edge spot fixture.

Follow spot: A type of lighting fixture used to highlight a performer, and follow them around onstage if necessary.  Often a performer will get both a front and a back spot to provide highlights and depth.

Fresnel: A Fresnel is a type of soft edge wash unit that uses a Fresnel lens typically used for top and back light, although sometimes it is used for soft front light (at a short to medium throw) if other fixtures aren’t available.  One of the defining characteristics of a Fresnel fixture is the ability to ’spot’ or ‘flood’ the beam of light by adjusting the position of the lamp and reflector in relation to the lens.  The closer the lamp/reflector is to the lens the wider the beam will be (flooded), and the further away the lamp/reflector is the smaller the beam will be (spotted).  Fresnels come in all shapes and sizes, but in the theatrical world they typically come in 3″, 6″, 8″, and 10″ varieties, with lamps ranging in power from 150W to 2000W.

Inkie: The name given to the three inch Fresnel.  A cousin to the birdie.

LED: Light Emitting Diode.  A very energy efficient light source that is becoming more and more popular as the technology becomes more efficient.  LED fixtures use a very low amount of watts but don’t have the brightest throw.  But the technology is getting better and the lights are getting brighter.  Also, the ability to mix colors by using different colors of LEDs is getting better and more efficient.

Lighting Fixture: The generic catch-all term for any device that outputs light, be it a conventional fixture, practical, or automated fixture.  Synonymous with ‘unit’.

MR 16 (PAR 16): The smallest size of PAR lamp used in theater.  This type of light is ideal for hiding inside of set pieces because it provides a surprisingly bright soft-edge pool of light.  I’m not 100% sure as to the origin of the term, but sometimes this type of light is called a ‘birdie’.  I think the term comes from the fact that it looks like a little PAR can–one could say it’s “one under Par” which every golfer knows is called a ‘birdie’.

Non-Dims: Refers to lighting fixtures or other electrical devices that don’t dim

PAR: Parabolic aluminized reflector.  Essentially, a PAR can is a car headlight in a paint bucket.  I mean, it’s a little bit more refined and machined than that, but if you took a car headlight, and put it inside a paint bucket, you’d get a very similar look.  The light output is based on the lens type which comes in Wide Flood (W), Medium Flood (M), Narrow Spot (NSP), and Very Narrow Spot (VNSP).  The narrow lenses come out in a smaller, tight beam, in a more circular fashion.  The wider lenses throw the light out in a more football shaped beam.

Because the lens throws out in an oval instead of a circle, sometimes a designer will want to change the orientation of the beam.  Changing the orientation is called ‘rotating the bottle’.

PAR Bar: An aluminum bar on which multiple PAR lamps (usually 6) are hung and wired into.

Practical: A term referring to any ‘actual’ or ‘household’ lamp that is used on stage.  For example, if you took your bedside lamp and put it onstage, it would be called a practical.  Or if you took that fancy sconce in your office off the wall and put it onstage, it would also be called a practical.  A practical fixture may or may not actually light up, although typically the light they output is just for show, and they are supplemented by stage lighting.  For example, if you wanted to use that bedside lamp to give the illusion that someone is in bed, reading by that lamp light, a designer would still need to add in a few stage lights to fill in and bring up the intensity of the effect.

Scoop: A scoop is a large, simple lighting fixture with no lens, a very large high-wattage lamp, and a dome shaped reflector.  The light output is a very wide, very soft, basically unfocusable glob of light.  Because the light output is so wide and unwieldy, most theaters will end up using scoops as work lights.

Spare: Any type of lighting fixture that is put into the plot that doesn’t have a specific purpose, but is still hung, plugged in, and tested.  It is set aside in case anything comes up that the designer realizes they haven’t initially planned for.

Special: A light that is not part of a system that is used to highlight a moment in the action or to isolate a performer.  Often, a special is only used for one moment during a show.  For example, if a performer needs to step downstage to deliver a soliloquy, a designer may place a special that shines downstage center that the actor can step into.  All the rest of the stage lights may dim when the special comes up to full to help highlight and isolate the moment.

Striplight: A striplight is a multi-circuit lighting instrument, consisting of a row of lamps consisting of either 3 or 4 circuits.  Strips are commonly used as low front light at the edge of the stage, or as uplight for a scrim or cyc drop upstage.

Work Light: A work light is a bright, wide flood, white light that is used anytime that work is going on in a theater.  Work lights are designed so that they can be turned on/off by anyone, and don’t require a trained electrician to deal with.  They are cheap and easy to re-lamp if they burn out.  ‘Works’ are turned on instead of stage lights because the gel used in stage lights burn out fairly quick.