Glossary of Terms - G

A glossary of terms covering lighting, audio, vision and staging in the event and theatrical industry.

There can be a number of meanings for some terms which can vary from country to country and manufacturer to manufacturer. Information within this guide is indicative and every situation can require a different approach and solution. All care has been taken, however, Image Group NZ accepts no responsibility for inaccuracies. If you have any suggestions, comments or queries regarding this list please contact us.

G

GAFFA TAPE
Ubiquitous sticky cloth tape. Most common widths are .5" for marking out areas and 2" (usually black) for everything else. Used for temporarily securing almost anything. Should not be used on coiled cables or equipment. Originally known as Gaffer's Tape, from the Gaffer (Master Electrician) on a film set.

GAIN
An increase in strength or amplitude (voltage) in a signal. The increase in signal power that is produced by an amplifier; usually given as the ratio of output to input voltage, current, or power expressed in decibels.

GAMMA CORRECTION
A variation in the input signal to provide a linear relationship between signal source and display output.

GATE

    The point of focus in a profile spot where the shutters are positioned and where an iris or gobo can be inserted.
    A single base section of a folding rostrum system.

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. Also known as a Scrim.

GBPS
Gigabits per second. 1 Billion bits per second.

GEL OR GELATINE
See COLOUR FILTER.

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. See SPECIAL.

GENERIC
Standard stage lighting instruments, rather than moving lights or other effects. (e.g. "There are 40 instruments in the rig - 20 moving lights and 20 generics").

GERB
See PYROTECHNICS.

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. (aka Load out or Bump out.)

GFI / G.F.I.
(US) Ground Fault Interruptor. See RCD.

GHOST LOAD
A lamp or group of lamps used to smooth out the waveform from electronic dimmers when using an inductive load(ballasts, transformers) rather than a resistive load (lamps).

GHOSTING
A method of determining the exact position of a followspots beam by faintly exposing it on a darker area of the stage or upon the drapes. Often done just before a "pick up" so the operator can have the lantern aimed and ready. A more professional practice is to use sights to line up a followspot.

GHOSTLIGHT / GHOST LIGHT

    To stop people tripping over bits of scenery when they come into the theatre in the morning.
    Also refers to the light emitted by a lantern when a dimmer has not been "trimmed" correctly, and is leaking.
    Also known as the "Equity Light". See link below for more information.

GLOVES
Used when lifting heavier lanterns or other equipment.

GLS
General Lighting Service. Lamps designed for general everyday use.

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, cityscapes 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.

There are a few possible origins for the word GOBO:

    It came from the early days of Hollywood. When the Director of Photography wanted daylight excluded from some area of the set, he'd say "GO BlackOut". Loads of people would run around putting black material between the sun and the set.
    It stands for Graphical Optical BlackOut.
    It is short for Go-Between, as the gobo goes between the lamp and the lens.
    It is short of GO Before Objective (i.e. it goes before the Objective lens).

Material from 1967 uses the word "MASK", and no mention is made of "GOBO", so we can assume the word wasn't in widespread use then. In the US TV/Film industry, a Gobo is a piece of material used to mask or block light, placed in front of a lantern (also known as a SHADOW MASK) and a Cookie (short for Cucaloris(from the Greek kukaloris: the breaking up of light)) is the same as a UK Gobo. PATTERN and TEMPLATE can also refer to a gobo in some areas. In the film industry, the word gobo can be used as a verb (e.g. "We need to gobo off that light so the camera doesn't see it").

GOBO HOLDER
A metal plate designed to hold a gobo of a particular size in a lantern of a particular type.

GOBO ROTATOR
See EFFECTS, LIGHTING

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.

GRAND MASTER
See MASTER.

GROUND
A heavy cable connected to earth via a metal copper stake for the purpose of grounding electrical equipment. In the U.S. a third wire in our electrical system is connected to this earth ground to provide a means of connecting the chassis of electrical equipment to the earth ground and thus provide protection against hazardous electrical shock.

GROUND LOOP
Hum caused by return currents or magnetic fields from relatively high-powered circuits or components which generate unwanted, noisy signals in the common return of relatively low-level signal circuits. A potentially detrimental loop formed when two or more points in an audio system that are nominally at ground potential are connected by a conducting path.

GROUND PLAN
Scaled plan showing the exact position (seen from above) of all items standing on the stage floor and indicating the position of items suspended above. Typical scales are 1:24 (.5" to 1 foot) or, metrically 1:25 (1cm to .25m). Venues have a base plan showing proscenium, walls, seating etc on which individual set and lighting plans can be drawn.

GROUNDROW

    A long piece of scenery positioned at the base of a backcloth usually to mask the very bottom of a cloth or lanterns lighting a cloth.
    Compartmentalised floodlight battens at floor level used to light the bottom of skycloths etc.

GROUP
A subdivision, permanent or optional, of a lighting board control preset, or a sound desk.

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