Theatre Jargon Buster

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Asymmetric: Or off set reflector. This gives a light intensity bias to the output of the light, normally found in modern floodlights.

Axial: Orientation of the filament within the modern range of Tungsten Halogen Lamps, where the filament lies in the same horizontal as the lens tube i.e. at right angles to the reflector.

Barndoor: Attachment that slots on to the front of non-profile lanterns to contain spill and softly shape the beam.

Batten: Older style of floodlight unit, suspended above the stage area mainly to light the cyclorama or back cloth.

Blackout: Lighting condition in which all controllable lights are turned off.

Call: To call or cue the different technical departments. Usually a member of the stage management team will be responsible for this.

Cap: The cap/connection end of the lamp, sometimes pins, sometimes a bayonet fitting.

Carrier: Lens carrier, the mechanical holder for one or more lenses, within the lens tube of a profile lantern, providing the ability to move the lens back and forwards.

Clipping: Where a sound signal is much too loud for a mixer or processor to handle. The top portion of the sound wave is clipped off due to the dynamic range of the signal being more than the equipment allows.

Coaxial cable: Coaxial cable, or coax, is an electrical cable with an inner conductor surrounded by a flexible, tubular insulating layer, surrounded by a tubular conducting shield. The term coaxial comes from the inner conductor and the outer shield sharing the same geometric axis. Coaxial cable is used as a transmission line for radio frequency signals, in applications such as connecting radio transmitters and receivers with their antennas, computer network (Internet) connections, and distributing cable television signals. One advantage of coax over other types of radio transmission line is that in an ideal coaxial cable the electromagnetic field carrying the signal exists only in the space between the inner and outer conductors. This allows coaxial cable runs to be installed next to metal objects such as gutters without the power losses that occur in other types of transmission lines, and provides protection of the signal from external electromagnetic interference. Coaxial cable differs from other shielded cable used for carrying lower frequency signals such as audio signals, in that the dimensions of the cable are controlled to give a precise, constant conductor spacing, which is needed for it to function efficiently as a radio frequency transmission line Colour filter: A thin acetate film, which will withstand high temperatures generated by the lantern. Available in a wide range of colours.

Colour magazine: Usually associated with Followspots, providing a mechanical means of placing colour into the beam of light.

Comms/Cans: Abbreviation for Communications System, a low power amplification system providing personal headset equipment otherwise known as Talkback, worn by members of the technical team to send & receive instructions (cueing).

Compressor: A processing method used to reduce the dynamic range of an audio signal. Can also be used as a limiter.

Coverage: The term for coverage of lighting over a given area, sometimes called a Wash.

CSI: Compact Source Iodide – type discharge lamp used in modern Followspots.

Cue: A cue is given by the Stage Manager to action a lighting, sound, set or scene change.

Cyclorama: Usually a plain white cloth at the back of the stage. Also called a Cyc.

Decibel (dB): A relative unit of measurement for sound.

DeMultiplex: Digital Control Signal, also known as DeMux or DMX. Used as the control protocol between the control desk, dimmers and other technical equipment.

Dimmer: Electronic device to limit the flow of electrical current, used in multiples. Modern dimmers are controlled by DMX.

Discharge lamps: An enclosed arc light source used in Followspots and larger TV specification lanterns.

Dynamic range: The range of signal levels that an audio system or piece of audio equipment is capable of handling.

EQ: Equalisation – used on sound desks and editing software to boost or reduce specific frequencies within the audible spectrum.

Fader: The slider control that you see on all lighting and sound desks that is used to control level or intensity. Also called Sub-masters on lighting desks.

Flat Field: The ability to distribute the light output (in a Profile lantern) over the whole of the image, specifically important when using Gobos.

Flats: Main parts of scenery, usually reinforced plywood or material.

Floodlight: Any lantern having an open front i.e. no lens.

Floor Can: Parcan lantern designed to be used from a floor position on a wee stand.

Focus: The art of positioning a lantern in a very exact manner, critical in the process of the overall lighting job.

FOH: An acronym for Front of House, usually referring to the auditorium.

Followspot: High output profile lantern type, used by hand to highlight particular members of the cast on stage.

Footlights: Old, now mostly redundant form of floodlight, found at the front floor position of a proscenium arch stage. Also known as Floats.

Fresnel: One of the five main categories of lanterns.

Frequency: Used to express the rate at which a sound or light wave reverberates, measured in Hertz (Hz).
- 1 mHz (millihertz) = 0.001 revolutions per second
- 1 Hz = 1 revolutions per second
- 1 kHz (Kilohertz) = 1,000 revolutions per second
- 1 MHz (Megahertz) = 1,000,000 revolutions per second
- 1 GHz (Gigahertz) = 1,000,000,000 revolutions per second
- 1 THz (Terrahertz) = 1,000,000,000,000 revolutions per second

Gain: Essential a very broad volume control that is used to raise or lower the level of an audio signal pre-fade.

Gate: Opening in the top of the lens tube of a profile lantern, behind the lenses, into which accessories such as Gobos or an Iris Diaphragm may be inserted.

Gobo: Metal or glass plate with a pattern or image etched into it. Used in a profile lantern or intelligent fixture to project an image.

Ground row: Floodlight unit, mainly used to light the cyclorama or back cloth being floor mounted.

HMI: Halide Metal Iodide is another form of discharge lamp often used in Followspots and intelligent fixtures.

Hook Clamp: Sometimes called a G Clamp, this is the suspension link between the lantern and the lighting bar.

Iris diaphragm: Used with a Profile lantern, to restrict the aperture/light output of the lantern.

Lamp House: Rear section of the lantern, containing the lamp and reflector.

Lens Tube: Front section of a Profile lantern, containing one or more lenses.

Light curtain: A line of low voltage narrow angle output lamps, contained in one housing, normally used in multiples, producing a narrow strip of high intensity light.

Limiter: A unit or processing method that restricts the maximum volume of an audio signal. Mainly used to protect speaker systems.

Masking: Black material or flats that are positioned around the set to "mask off" parts of the space that from the audience

MIDI: Musical Instrument Digital Interface.

Moving Lights: These fall into two types: moving head and moving mirror. The moving head requires the whole of the lamp housing to pan and tilt, whereas the moving mirror has the lamp housing fixed and operates a motorised mirror in front of the lens. These are also known as Intelligent Fixtures.

MSR: Medium Source Rate Earth type of discharge lamp often used in modern Followspots.

Muticore: A multicore cable is a generic term for an electrical cable that has multiple cores. The term is normally only used in relation to a cable that has more cores than commonly encountered. For example, a four core mains cable is never referred to as multicore, but a cable comprising four coaxial cables in a single sheath would be considered a multicore.

The term multicore cable or "Multi" is frequently used in the theatrical industry to refer to an audio or power multicore cable

Normalization: The process of adjusting the volume of a group of audio files so that they all play at the same volume.

Ohms Law: The calculation by which the amperage load of a circuit can be found.

Pan and Tilt: The act and ability to swivel and angle the lantern.

PAR: Parabolic Aluminised Reflector. One of the five main categories of lantern.

Peak: Lighting – where a central hot spot may be desired within the image.
Sound – when an input signal is too high for the mixing or processing equipment to handle, creating distortion. See Clipping.

Plotting: The work of setting up different lighting states and the changes between them. A plotting session is an essential part of every show.

Preamp: Hardware that boosts the level of an audio signal to a set level before being sent to the main amplifier.

Pebble Convex Lantern: Also called a PC, this is another of the five main categories of lantern.

Production Desk: Usually in the auditorium during rehearsals, this is the operational centre during technical set-up.

Profile: One of the five main categories of lantern.

Prompt book: Copy of the script set out to contain notation for all technical cues.

Ray Light: Reflector used in PAR lanterns, producing a very narrow angle beam.

Reflector: All lanterns have a reflector behind the lamp to enhance and intensify the light output.

Rigging: The act of rigging is to place lanterns & equipment, usually at height.

Rig Plan: Large paper plot showing the layout and detailed information on all lanterns in a lighting rig.

Safety Bond: The modern replacement for the safety chain, providing a secondary safety suspension. Note that wire rope safety bonds are marked with the maximum weight of lantern that they are suitable for

Shutter: Within a Profile lantern, one of a set of four shutter blades used to shape the beam of light.

Spill: Unwanted elements of light, often controlled by the use of Barndoors.

SWL: Safe Working Load. Calculated by dividing the Minimum Breaking Load by a Safety Factor (see also WLL)

Stencil: Scale representation of lantern shape/types, used in drawing rig plans. Modern CAD packages are now more commonly used in design.

Tabs: Or Tableau Curtains. These may be the main Proscenium Arch curtains, often called House Tabs, or a pair of curtains crossing the stage at any position. Usually blacks.

Trunion Arm: Also known as the Yoke, it surrounds the lantern and provides the main suspension position.

Wash: See Coverage.

WLL Working Load Limit. An absolute limit to the item's strength (see also SWL)

Zoom Profile: The use of two independently movable lenses within a Profile lantern.

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