Technical Glossary

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Advance Bar - In the UK, a lighting bar positioned just downstage of the proscenium arch. This Bar in the ADC is referred to as Bar Zero. Also known as ANTE PROSCENIUM.

Ambient Light - Background light in the venue when no stage-lighting sources are on.

Attributes - The controllable parameters of a moving light are know as the attributes. All moving lights will have a pan & tilt, with many having colour wheels, gobo selection, gobo rotation etc. as additional attributes.

Backlight - Light coming from upstage, behind scenery or actors, to sculpt and separate them from the background.

Bar - The horizontal metal tube hung from flying lines from which lighting equipment and scenery may be suspended. It is also known as a BARREL. When vertical, it is known as a BOOM.

Barndoors - A rotatable attachment consisting of two or four, hinged metal flaps which are fixed to the front of a Fresnel or PC type lantern to cut off the beam in a particular direction(s). Profile lanterns use SHUTTERS to achieve a greater degree of control and accuracy. Barndoors are also available for parcans and birdies. BLACKWRAP can be used to reduce additional light spill where barndoors aren't doing the job.

Birdie - A compact low voltage display luminaire containing a Par 16 or MR16 lamp. So called because it is similar to, but much smaller than, the Parcan, and is hence "one under Par". (In golf terminology, a birdie is a score one below the par for that particular hole). Due to its compactness, the birdie is ideal for concealing in pieces of set or as downstage uplights. The beam angle can be narrow - a range of different lamps are available with differing beam widths.

Black Hole - An accidentally unlit portion of the stage. Otherwise known as a shaft of darkness or SOD.

Blackout - A complete absence of stage lighting. Blue working lights backstage should remain on and are not usually under the control of the board, except during a Dead Blackout (DBO), when there is no onstage light. Exit signs and other emergency lighting must remain on at all times.

Bleed Through - Transformation from a scene downstage of a gauze to another scene upstage, by slowly crossfading lighting from downstage to upstage. If a gauze is lit steeply, or from the sides, it will appear solid. If this light is turned off and light added to the set upstage of it, it will disappear.

Blind Plotting - The facility on some lighting control desks for the operator to make changes to the plot, without affecting the state on stage.

Blinders - 1) Lamps arranged around the stage directed into the auditorium, originally to prevent spectators seeing the stage during scene changes when the house tabs were not lowered. Now used for effect in rock concerts etc. 2) A strip of dense black material fastened behind a crack between two flats or scenic pieces to prevent light leak. Cloth hung behind a gauze to prevent transparency before the effect is required.

Boom - Vertical scaffolding pole (usually 48mm diameter) on which horizontal boom arms can be mounted, carrying lanterns. Often used behind wings for side-lighting etc. Booms have a base plate (known as a TANK TRAP) or boom stand at the bottom and are tied off to the grid or fly floor at the top (not always necessary for short booms). Booms can also be fixed to the rear of the proscenium arch (Pros. Boom) or hanging from the ends of lighting bars.

Border - A narrow horizontal masking piece (flattage or cloth), normally of neutral colour (black) to mask the lighting rig and flown scenery from the audience, and to provide an upper limit to the scene. Often used in conjunction with LEGS.

Breakup - A commonly used abstract GOBO which gives a textured effect to the light, without throwing a specific pattern onto the stage. Used to add interest to light beams. A leafy breakup is used for outdoor scenes / forests / spooky wood etc. to break up the light on the actors faces.

Bump - A flash or sudden jump in light level (a snap cue).

Bump Cue - A lighting cue that instantly bumps the lighting up to a brighter level. Usually at the end of a musical number to draw the applause.

Cans - 1) Headset earpiece, microphone and beltpack used for communication and co-ordination of technical departments during a performance. (e.g. "DSM on cans", "Going off cans", "Quiet on cans!"- a DSM favourite).

Chase - A repeated sequence of changing lighting states. A chase can be produced easily by the effects functions of a computerised lighting desk.

Chief Electrician - The senior member of the theatre's stage lighting team, although not necessarily the lighting designer. Often abbreviated to CLX. In common with many theatre jobs, the actual duties of the Chief Electrician vary from theatre to theatre. Some chiefs are responsible for electrical maintenance of the building, some design the lighting for nearly every in-house production, some design no lighting at all.

"Chins on stage" - A warning, often abbreviated to "Chins" when things are being flown out/upwards.

Circle Fronts - A permanent front of house lighting position in older proscenium theatres. A number of spotlights, sometimes fitted with colour changers, are recessed into the front of the circle balcony above the stalls. Sometimes known as the Balcony Rail position.

Cleaners - Auditorium working lights. Used for cleaning and setting up the auditorium before the house lights (usually more atmospheric) are switched on.

Colour Changer - 1) Scroller, where a long string of up to 16 colours is passed horizontally in front of a lantern. Remotely controlled by the lighting desk. Some scrollers have cooling fans to prolong the life of the gel string. Stronger colours will burn out faster without cooling, or if the focus of the beam is concentrated on the gel. If colours aren't lasting very long in scrollers, try changing the focus of the lantern. HEAT SHIELD clear gel should be used between the lens and the colour scroller to absorb some of the heat. 2) Wheel : Electrically or manually operated disc which is fitted to the front of a lantern with several apertures holding different colour filters which can be selected to enable colour changes. Can also be selected to run continuously. 3) Semaphore, where framed colours are electrically lowered into place in front of the lantern. Remotely controllable. Can perform additive colour mixing by lowering two colours into position at the same time. 4) Magazine : Manual semaphore-type device used on the front of a followspot.

Colour Mixing - Combining the effects of two or more lighting gels: 1) Additive : Focusing two differently coloured beams of light onto the same area (eg Cyc Floods). Combining colours in this way adds the colours together, eventually arriving at white. The three primary colours additively mix to form white, as do the complementary colours. 2) Subtractive : Placing two different gels in front of the same lantern. Subtractive mixing is used to obtain a colour effect that is not available from stock or from manufacturers. Because the ranges of colour are so wide, the need for subtractive mixing is reducing. Combining colours in this way reduces the light towards blackness. The three primary colours mix subtractively to form black (or to block all the light).

Counterweight rigging system/Counterweights - In a typical counterweight fly system, an arbor (carriage) is employed to balance the weight of the batten and attached loads to be flown above the stage. The arbor, which carries a variable number of metal counterweights, moves up and down vertical tracks alongside an offstage wall. In some lower-capacity fly systems, cable guide wires are used instead of tracks to guide the arbors and limit their horizontal play during vertical travel (movement).

Cross Fade - Bringing a new lighting state up whilst bringing the previous one down, so that the new one completely replaces the old one. Also applies to sound effects / music. Sometimes abbreviated to Xfade or XF. A DIPLESS CROSSFADE occurs when the lighting doesn't dip significantly between states, which results in a more subtle transition.

Cue - 1) The command given to technical departments to carry out a particular operation. E.g. Lighting Cue, Fly Cue or Sound Cue. Normally given by stage management, but may be taken directly from the action (i.e. a Visual Cue). 2) Any signal (spoken line, action or count) that indicates another action should follow (i.e. the actors' cue to enter is when the Maid says "I hear someone coming! Quick - Hide!")

Cue Light - System for giving technical staff and actors silent cues by light. Cue lights ensure greater precision when visibility or audibility of actors is limited. Sometimes used for cueing actors onto the set. For technical cues, lights are normally now used just as a backup to cues given over the headset system. In the UK, a flashing Red light means stand-by or warn, green light means go. The actor / technician can acknowledge the standby by pressing a button which makes the light go steady.

Cue to Cue - (also known as 'Topping and Tailing') Cutting out action and dialogue between cues during a technical rehearsal, to save time.

Cueing - There is a standard sequence for giving verbal cues: 'Stand-by Sound Cue 19' (Stand-by first) 'Sound Cue 19 Go' (Go last).

Cyc Flood - A floodlight, usually with an asymmetrical reflector, designed to light a cyc or backcloth from the top or bottom. The asymmetric reflector helps to throw light further down the cloth, producing a more even cover.

Dead - 1) A pre-plotted height for a piece of scenery or lighting bar - 'that bar's on its dead'. The positional indicators on the rope (either PVC tape, or more traditionally cotton tape passed through the strands of the rope) are called DEADS. Sometimes flying pieces are given a number of extra deads, that may be colour coded, in addition to the 'in dead' (lower) and 'out dead' (higher - out of view). In the US, TRIM has the same meaning. Fluorescent ribbon is often used, through the fibres of the rope. The fluorescent colour shows very clearly under UV light, which is often used to light fly floors. 2) Scenery or equipment not needed for current production - 'that table's dead'. 3) An electric circuit that has been switched off or has failed - 'the circuit's dead, you can change the lamp now'

Dim Out - Reduction of lighting level for a scene change, that isn't quite a BLACKOUT.

Dip - 1) Small covered trap at stage level containing electrical outlets. (US equivalent is FLOORPOCKET) 2) Any dimmer outlets at floor level around the stage (e.g. 'What's the nearest dip circuit to downstage left so I can plug the birdie in?') 3) Lighting equipment on stands at stage level. (e.g. 'We're just focussing the dips now') 4) Low lighting intensity when cross fading between two higher states - 'there's a dip between these two states'. 5) Transparent lacquer for colouring lamp bulbs - known as 'Lamp Dip'.

Doofer - An object or tool that you're not sure of the correct name for. For example, 'Pass me the doofer so I can sort this thingy'.

Downlight - A light from directly above the acting area.

Downstage - Towards the audience in a proscenium arch theatre.

Fade - A fade is an increase, diminishment or change in lighting or sound level.

Fill Light - Light which ills the shadows that key light creates (especially used in TV and film lighting).

Flagging - When focussing lighting, flagging means waving your hand in and out of the beam of a lantern/instrument in order to see where the beam is hitting on stage. Flagging is particularly useful in high ambient light levels. (e.g. 'Can you flag that please ?') Term probably originates from a FRENCH FLAG.

Flash Box - A small box containing the socket into which a pyro cartridge is plugged. Also known as a flash pod or firing pod.

Flash Out/Flash Through - Method of checking whether lanterns are functioning properly by flashing them on one at a time. It is good practice to flash lanterns to 70%, rather than Full to preserve lamp life.

Flood - 1) A lensless lantern that produces a broad non-variable spread of light. Floods are used in battens, or singly to light cycloramas or large areas of the stage. 2) To increase the beam angle of a Fresnel or PC by moving the lamp and reflector towards the lens. 'Flood that a bit, please!'. The opposite movement is called Spotting.

Floor Light - Lanterns mounted on low stands at stage level so they provide uplight, casting shadows across the stage.

Fly system - Sometimes known as a theatrical rigging system is a system of rope lines, blocks, counterweights and related devices within a theatre that enables a stage crew to fly quickly, quietly, and safely, components such as curtains, lights, scenery, stage effects and, sometimes, people.

Focus - 1) The session when all the lanterns / instruments in the rig are angled in the correct direction, with the correct beam size. 2) Description of how sharply defined a light beam is ('give that profile a sharp focus') 3) Control on projection equipment used to change the focus.

Focusing - The process of adjusting the direction and beam size of lanterns. Does not necessarily result in a 'sharply focused' image.

FOH / Front of House - 1) Every part of the theatre in front of the proscenium arch. Includes foyer areas open to the general public. 2) All lanterns which are on the audience side of the proscenium and are focussed towards the stage. The backstage areas of the theatre are known as Rear of House (ROH).

Follow Cue/Follow-On Cue - A cue that happens so soon after a previous cue, that it doesn't need to be cued separately. The follow-on can be taken by the operator once a previous cue is complete, or a lighting or sound cue can be programmed to happen a specific time after a previous cue. Fly follow-on cues are often taken as soon as the operator has completed a previous cue. Often abbreviated to F/O.

Followspot - Usually, a powerful profile lantern usually fitted with its own dimmer, iris, colour magazine and shutters mounted in or above the auditorium, used with an operator so that the light beam can be moved around the stage to follow an actor. Sometimes a beam light or other lantern may be used in the same way. Powerful followspots use discharge lamps which cannot be dimmed, so these followspots have mechanical dimming shutters to dim the light output.

Foot - 1) The action of bracing the bottom of a ladder while a colleague climbs it (e.g. 'Can you foot this for me please? I'll only be a couple of minutes'). 2) Holding the bottom edge of a flat with your foot while a colleague raises the top of it to a vertical position.

Footlights - 1) A compartmentalised flood batten sometimes recessed into the front edge of the stage, used to neutralise shadows cast by overhead lighting. Before battens were used, individual light bulbs with ornate shades to shield the glare from the audience were used. Modern lighting equipment renders footlights virtually obsolete except for period/special effects. 2) A comedy group. Not related to tech at all. Lights up, lights down.

Frost - A diffusing filter used to soften the edges of a light beam. Frosts are commonly used in profiles in front of house positions to achieve the same beam edge quality in all lanterns. Different strengths of diffusion frost are available from many colour filter manufacturers.

Full Up - A bright lighting state with general cover lanterns at 'full' (100%) intensity.

Gaffer/Gaffa Tape - Ubiquitous sticky cloth tape. Most common widths are .5 inch for marking out areas and 2 inch (usually black) for everything else. Used for temporarily securing almost anything. Should not be used on coiled cables or equipment. Also known as Duct Tape.

Gauze - Cloth with a relatively coarse weave. Used unpainted to diffuse a scene played behind it. When painted, a gauze is opaque when lit obliquely from the front and becomes transparent when the scene behind it is lit . Many different types of gauze are available; Sharkstooth gauze is the most effective for transformations, because it is the most opaque. Vision gauze is used for diffusing a scene and for supporting cut cloths.

Gel - A sheet of plastic usually composed of a coloured resin sandwiched between two clear pieces. The coloured filter absorbs all the colours of light except the colour of the filter itself, which it allows through. For this reason, denser colours get very hot, and can burn out very quickly.

General Cover - Those lanterns in a rig which are set aside purely to light the acting areas. The stage is normally split into a number of areas for this purpose, which can then be isolated or blended together as required by the director.

Get-Out - Moving an entire production out of the venue, and into either a large waste-disposal skip, or into transport. Usually preceded by the strike.

Gobo - A thin metal plate etched to produce a design which can then be projected by a profile spotlight. There are hundreds of gobo designs available - common examples are breakup (foliage), windows and scenic (neon signs, city scapes etc.). The image can be used soft focus to add texture, rather than a defined image. A number of composite gobos in different coloured lanterns can, with careful focusing, produce a coloured image (e.g. a stained glass window). Greater detail can be achieved using a glass gobo, which consists of a thin layer of aluminium etched onto glass.

"Going Dark" - Warning to people on stage that the lights are about to be switched off. Normally said during lighting plotting sessions or technical rehearsals. Obviously should not be done if there is any risky work on stage, or if anyone is up a ladder / using power tools / working on platforms / rehearsing choreography etc.

Green Room - Not literally a room that is green, but a lounge area for performers and/or technicians.

Gridiron/Grid - An open floor, usually made from light steel channels or grating, that is located near the roof steel. It provides mounting locations for rigging equipment and access to that equipment for inspection and maintenance.

Hazer - A Haze machine, Hazer or Diffusion Fogger is used to produce an atmospheric haze, rather than clouds of smoke, and is used by many lighting designers to reveal airborne light beams.

Heads - the top lantern on a lighting boom.

"Heads on Stage" - A shouted warning (often just 'Heads!') for staff to be aware of activity above them. Also used when an object is being dropped from above.

"Heads up!" - a warning called when something is wrong, usually something falling from the grid.

Heatshield - Made by Rosco, Heat Shield is a special clear gel which when placed between a lamp and a coloured gel, dissipates a large amount of heat to give the gel a longer life. There must be an air gap between the Heat Shield and the gel, or it will not be effective.

Hemp Rigging System/Hemps - A hemp fly system, so named for the manila hemp rope that was once common in theatrical rigging, is the oldest type of fly system. In a typical hemp system, a "line set" consists of multiple hemp lines running from a batten above the stage up to the grid, through loft blocks to a headblock and then down to the fly floor where they are tied off in a group to a belaying pin on the pin rail. The lift lines and hand (operating) lines are one and the same. Typically, a lift line runs from the sand bag (counterweight) assigned to a specific line set, up to "a single loft block" above the fly floor and back down to the fly floor. Hemp systems are also known as rope line systems, or simply as rope systems.

Hook Clamp - A clamp with a wing bolt for hanging a lantern on a horizontal lighting bar, so that it hangs below the bar. Hook Clamps should not be used to overhang items above a lighting bar. A BOOM ARM can be rigged on a lighting bar (horizontal) or a boom (vertical) to rig a lantern adjacent from the bar / boom. Alternative clamps are available to rig a lantern above a bar.

Hot Spot - The brightest part of the beam from a lantern, usually showing the centre. Profile lanterns have a Field control which enables a beam to be flattened so it has no hot spot.

House Lights - The auditorium lighting which is commonly faded out when the performance starts.

In - When flying, down onto stage.

Inhibit - A way of taking control of a rogue lantern (or lanterns) at the lighting desk during the operation of a show and removing them from any further lighting states, until the inhibit is removed. Can also be used for removing the front of house lighting from a curtain call state.

Iris - Adjustable aperture which, when placed in the gate of a profile lantern, varies the size of a beam of light. Originally, iris diaphragm. Most followspots have an iris permanently installed.

Isolating - The process of decreasing the sensitivity of smoke detectors for the duration of a performance where smoke effects are used.

Key Light - The dominant light source/direction in a naturalistic lighting state. In a sunny drawing room, the key light would be through the window, for a naturalistic exterior scene the direction of the key light could change as the sun progressed across the sky. Especially used in film and TV lighting.

Kill - To switch off (a light/sound effect); to strike/remove (a prop).

Lantern - 1) General term for unit of lighting equipment including spotlight, flood etc. Term now being replaced by the internationally recognised "luminaire" (esp. Europe) or "instrument" in the US. 2) Glazed section of roof usually in haystack form over the fly tower that automatically opens in the case of fire. An updraught is created which inhibits fire from spreading quickly into the auditorium, and prevents build-up of smoke at stage level.

Light Curtain - A lighting effect which, when an area is diffused with smoke, produces a wall of light. Produced (usually) by a batten of low voltage PAR lamps wired in series.

Lighting Plot - The process of recording information about each lighting state either onto paper or into the memory of a computerised lighting board for subsequent playback.

Lighting State - The format of lighting used at a particular point in the production; a lighting 'picture'. A lighting cue is given by the stage manager which initiates the change from one lighting state to the next.

Limelight - An obsolete source of intensely bright light, most recently used in followspots. Derived from a burning jet of oxygen and hydrogen impinging on a rotatable cylinder of lime.

Limes - Followspots and their operators. This term is still in everyday use, although limelight is not.

LX - Short for Electrics. The department in the theatre responsible for stage lighting and sometimes sound and maintenance of the building's electrical equipment. Lighting cues in the prompt book are referred to as LX cues (abbreviated to LXQ).

LX Tape - Plastic insulating tape used for taping cables to bars and for securing coiled cables. Neater and cheaper than Gaffa tape. Also known as LX tape.

Matinee Gag/Mat Gag - An inside joke for the actors or technical team used during a show matinee. The idea is to throw each other off but not let the audience know.

Mids - The middle lantern on a lighting boom.

Out - When flying, up into the area above the stage.

Parcan - Type of lantern which produces an intense beam of light, ideally suited to "punching" through strong colours, or for special effect. The Parcan is literally a cylinder of metal (the "can") within which sits the PAR lamp (PAR stands for Parabolic Aluminised Reflector) which consists of the bulb, a reflector and a lens in a sealed unit.

Patch - 1) (verb) The act of plugging a lantern into a dimmer (e.g. 'Can you patch circuit 12 into dimmer 18 please'). 2) (noun) The system for connecting lanterns to dimmers (The Patch). The term also applies to sound - a PATCH BAY is used to connect outboard equipment into the sound desk and to connect sound desk outputs to amplifiers, and amplifiers to speakers.

Perches - Lighting positions (often on platforms) at each side of the stage, immediately behind the proscenium. Some theatres use the term for vertical boom positions in front of the proscenium in the house.

Pick-Up - 1) Device which, when attached to an acoustic musical instrument, converts sound vibrations into an electrical signal. 2) A way of describing the directional sensitivity of a microphone. An Omnidirectional microphone has equal pick-up from all around, a Cardoid microphone is more sensitive from the front, a Hypercardoid has very strong directionality from the front. A figure-of eight microphone picks up front and rear, but rejects sound from the sides. 3) The action of turning a followspot on a performer. (e.g. 'that was a good pick-up', 'your next pick-up is downstage left'). A BLIND PICKUP is on a moving performer and requires good hand-eye co-ordination. A SET PICKUP is on a specific area, is preset, and is made on a cue from the stage manager. A SIGHT PICKUP is made visually by the operator to a preset position.

Point Cue - A cue inserted during / after plotting between two existing cues. (eg 8.5 is inserted between cues 8 and 9). Most computer lighting desks have the ability to either insert an additional cue in a sequence, or to link to another cue out of the sequence, and then link back again.

Practical - Any object which appears to do onstage the same job it would do in life, or any working apparatus (eg light switch or tap). A window within the set which has to open is a practical window. Light fittings which have to light up on the set are called Practicals.

Preset - Anything in position before the beginning of a scene or act (eg Props placed on stage before the performance, lighting state on stage as the audience are entering.)

Preview - 1) A performance (or series of performances) before the 'official' opening night. Previews are used to run the show with an audience before the press are allowed in to review the show. This allows technical problems to be ironed out while ensuring the cast and creative team get audience feedback. Tickets are sold at reduced price and help to spread word of mouth interest in the show. 2) A function on some memory lighting control desks with video mimics. Preview enables the operator to see the levels of dimmers and other information in a lighting state other than that on stage.

Production Desk - Table in the auditorium at which director/designer etc sit during rehearsals (especially technical rehearsals). Usually has its own lighting and communications facilities.

Prompt Desk - the desk where the deputy stage manager sits and cues the show.

Prompt Side/ Opposite Prompt - Technical terms used to denote sides of the stage. Prompt Side (PS) is the side of the stage where the prompt desk sits (Stage Left). Opposite Prompt (OP) is the side opposite the prompt desk (Stage Right).

Pyrotechnics/Pyro - (Pyro) Chemical explosive or flammable firework effects with a manual detonation. Usually electrically fired with special designed fail-safe equipment. There are many different variations of pyrotechnic effects available. The categories are as follows: Theatrical Flash - a flash and a cloud of smoke Maroon: produces a very loud bang. Must only be detonated inside a bomb tank covered with a protective mesh. Gerb: version of the Roman Candle firework, throwing a shower of sparks into the air. Possibly named from the French 'Gerbe' meaning a sheaf of wheat, due to it's shape. All pyrotechnics should be used with close reference to local licensing laws, and the manufacturers instructions. Professional advice should be sought before the first use of effects. Some territories only permit licensed pyrotechnicians to use these devices.

Re-Rig - To change the lighting rig after the last performance of one show to the positions for the next show.

Restore - A cue to resume or return to any previous state, setting or function. (e.g. 'at the end of the dance number we restore to a warm general cover').

Rig - 1) The construction or arrangement of lighting equipment for a particular production.(noun) 2) Installing lighting, sound equipment and scenery etc for a particular show.(verb)

Safety Curtain - A fire safety precaution used in large proscenium arch theatres. it is sometimes referred to as an iron. Occupational safety and health regulations state that the safety curtain must be able to resist fire and thereby prevent (or at least hinder) fires starting on stage from spreading to the auditorium and the rest of the theatre. It should be tested immediately before a performance, and no pieces of set, scenery or props should be placed within its path. Some regions require the curtain to be shown to a percentage of the audience, usually during the interval, to prove its effective operation.

Shins - The lowest lantern on a lighting boom. Named because of the proximity of sharp parts of the lantern to the flesh of the lower leg. The other lanterns on the boom are known as MIDS and HEADS.

Smoke Machine - An electrically powered unit which produces clouds of white non-toxic fog (available in different flavours/smells) by the vaporisation of mineral oil. It is specially designed for theatre & film use.

Spill - unwanted light onstage.

Spot - 1) to reduce the beam size of a fresnel or pc lantern by moving the lamp further from the lens. (e.g. 'Could you spot that down a touch, please?'). 2) an abbreviation of spotlight.

Spotlight - General term for any lantern with a lens system.

Stage Left/Right - Left/ Right as seen from the Actor's point of view on stage. (ie Stage Left is the right side of the stage when looking from the auditorium.) Stage Right = OP (Opposite Prompt) Stage Left = PS (Prompt Side)

"Standby" - 1) A warning given to technical staff by stage management that a cue is imminent. The member of the stage management team calling the cues will say "Standby Sound Cue 12". Technicians acknowledge by saying "Sound Standing By". 2) A member of the cast of a musical or play who understudies one (sometimes more) of the principal roles but is NOT also in the chorus. A standby often will not even be required to be at the venue at each performance unless he/she is called in to perform in the role for which he/she is an understudy.

State - In lighting terms, a lighting 'picture' ; each lighting cue results in a different state (or a modified state).

Strike - 1) The final night of the last performance, when the technical team tears down the set, returns all rented materials, and wraps up the show. 2) Also a general term used when anything is removed permanently from the stage, which can apply to props, costume, set etc. A strike can also apply part way through a show (e.g. you can strike a piece of set in the interval so it's gone for Act II), but this use of the term is more rare.

Strobe - Device giving a fast series of very short intense light flashes which can have the effect of making action appear intermittent. Because strobe lighting can trigger an epileptic attack in sufferers, the use of a strobe must be communicated to the audience before the performance begins. Strobes should be synchronised so that they operate outside the dangerous frequency band 4 to 50 flashes per second. (i.e. a strobe should operate at less than 4 flashes per second, or more than 50 flashes per second). If the effect is momentary, this rule may be relaxed. Strobes must never be used in public areas where there are changes of level or steps.

Swatch - A sample of fabric to demonstrate the material to use on a costume or set design, or a sample of lighting gel. A catalogue of all the gel colours made be a particular manufacturer is called a SWATCH BOOOK.

Tabs - Originally "tableaux curtains" which drew outwards and upwards, but now generally applied to any stage curtains including a vertically flying front curtain (house tabs) and especially a pair of horizontally moving curtains which overlap at the centre and move outwards from that centre.

Technical Rehearsal/Tech/Tech Run etc. - Usually the first time the show is rehearsed in the venue, with lighting, scenery and sound. Costumes are sometimes used where they may cause technical problems (eg Quick changes). Often a very lengthy process. Often abbreviated to the Tech. A DRY TECH is without actors to rehearse the integration of lighting, scenic changes etc. It follows that a WET TECH is a full technical rehearsal with actors and all technical elements, although this term isn't used as often as DRY TECH. A PAPER TECH is a session without the set or actors when the technical and design team talk through the show ensuring everything's going to work as planned. Stage Managers can use this session to ensure all is written correctly in the Prompt Book.

Throw - Distance between a light source (e.g. lantern or projector) and the actor or object being lit.

Transformation - An instant scene change, often effected by exploiting the varying transparency of gauze under different lighting conditions.

Uplight - Light from below the actors - from a light source on the stage floor.

Upstage - Away from the audience in a proscenium arch theatre.

Visual Cue - A cue taken by a technician from the action on stage rather than being cued by the stage manager. Often abbreviated to "Vis".

Wash - 1) A lighting cover over the whole stage (e.g. 'We'll use the red wash for the hell scene') 2) A lantern which produces a large spread of softly focussed light.

White Glove - A role is said to be 'white glove' if the person is not required or expected to help with setting up equipment, only in the operation of it.

Wings - 1) The out of view areas to the sides of the acting area. The wings are best identified by their position on stage (e.g. "Clive exits through the downstage left wing") but they can be identified by number if there are too many exits, with the downstage wing starting as 1, with stage left and right added to identify the side (e.g. "Sarah exits 2L"). 2) Scenery standing where the acting area joins these technical areas.

Working Lights - 1) High wattage lights used in a venue when the stage / auditorium lighting is not on. Used for rehearsals, fit-up, strike and resetting. 2) Low wattage blue lights used to illuminate offstage obstacles and props tables etc. Known as 'Wing Workers', 'Blues' or 'Running Lights'.