The STAGE LIGHTING Guide

GLOSSARY

A

Acting area
The area of the stage setting within which the actor performs.
Advance bar
A spot bar hung within the auditorium, close to the proscenium.

B

Backlight
Light coming from behind scenery or actors to sculpt and separate them from their background.
Bar
Horizontal metal tube of scaffolding diameter for hanging lights (pipe in America).
Barndoor
Four-shutter rotatable device which slides into the front runners of fresnel and PC focus spots to shape the beam and reduce stray scatter light.
Battens
Lengths of overhead lighting floods arranged in 3 or 4 circuits for colour mixing.
Beam angle
Angle of the cone of light produced by a spotlight.
Beamlight
Lensless spotlight with parabolic reflector giving intense parallel beam.
Board
Contraction of switchboard or dimmerboard. The central control point for the stage lighting.
Boom
Vertical pole, usually of scaffolding diameter, for mounting spotlights.
Boom arm
Bracket for fixing spotlights to a boom.
Build
An increase in light intensity.

C

Channel
A control circuit, identified by number, from the 'board' to a light.
Channel access
The method (levers, pushes, keyboard, etc) in a memory system by which individual channels are brought under operator control.
Check
Decrease in light intensity.
Colour call
A listing of all the colour filters required in each lighting instrument.
Colour temperature
A method of measuring (in Kelvin units) the spectral content of 'white' light.
Control Surface
Any device such as lever, push, wheel, rocker, mouse, pen, cursor, etc, used as an interface between an operator's fingers and a processing system which activates dimmers or motors controlling lighting instruments.
Cross-fade
Lighting change where some of the channels increase in intensity while other channels decrease.
Cue
The signal that initiates a change of any kind. Lighting cue is a change involving light intensity alterations.
Cyclorama
Plain cloth extending around and above the stage to give a feeling of infinite space. Term is often rather loosely used for any blue skycloth, either straight or with a limited curve at the ends.

D

Dead
1) The plotted height of a piece of suspended scenery or bar of lights.
2) Discarded items of scenery.
Dichroic
Colour filters which work by reflecting unwanted parts of the spectrum rather than absorbing them in the manner of traditional filters.
Diffuser
A filter, often called a frost, which softens a light beam, particularly its edge.
Dimmer
Device which controls the amount of electricity passed to a light and therefore the intensity of that light's brightness.
Directional diffuser
A filter which not only softens the beam but spreads it along a chosen axis. Also known as a silk.
Director
Has the ultimate responsibility for the interpretation of the script through control of the actors and supporting production team.
Discharge lamps
Special high powered light sources whose use is normally restricted to follow spots and projection because of difficulties in remote dimming by electrical means. includes C.S.I., C.I.D. and H.M.I lamps.
Downstage
The part of the stage nearest to the audience.

E

Ellipsoidal
Strictly a type of reflector used in many profile spots but extended in North America to cover all profile spots.

F

Flood
Simple instrument giving a fixed spread of light.
Flys
Area above the stage into which scenery can be lifted out of sight of the audience.
Focusing
Strictly speaking, the adjustment of lights to give a clearly defined image; but usually used to cover the whole process of adjusting the direction and beam of spotlights in which the desired image may be anything but clearly defined.
FOH
All instruments which are 'front of house', i.e. on the audience side of the proscenium.
Follow spot
Spotlight with which an operator follows actors around the stage.
Fresnel spot
Spotlight with soft edges due to fresnel lens which has a stepped moulding on the front and a textured surface on the back.
Frost
A diffuser filter used to soften a light beam.
FUF
Full-up-finish. An increase to bright light over the last couple of bars of a musical number.

G

Gate
The optical centre of a profile spot where the shutters are positioned and where an iris or gobo can be inserted.
Gauze
Fabric which becomes transparent or solid under appropriate lighting conditions.
Gobo
A mask placed in the gate of a profile spotlight for simple outline projection. Also used, with softened focus, to texture the beam.
Groundrow
A low piece of scenery standing on the stage floor. Also lengths of lighting placed on the stage floor.
Group
A subdivision, temporary or permanent, of the channels in a control system.

H

Hook clamp
A clamp for fixing an instrument to a horizontal bar, usually of scaffolding diameter.
Houselights
The decorative lighting in the auditorium.

I

Instrument
A stage lighting unit, such as a spotlight or flood. An American term coming into increasing international use.
Iris
An adjustable circular diaphragm to alter the gate size in a profile spot. Also the muscle operated diaphragm in the human eye which adjusts the eye's aperture to changing light intensities.

K

Kilowatt
see wattage

L

Ladder
Framework in the shape of a ladder for hanging side lighting.
Lamps
The light source within an instrument, but sometimes used as an alternative to the word instrument.
Lantern
A lighting unit designed or adapted for stage use. A traditional word now being overtaken by 'instrument'.
Linear flood
A flood using a long thin double-ended halogen lamp, allowing the reflector to be designed for an increased beam spread.
Load
The lights controlled by an individual dimmer and limited by the rating of that dimmer.

M

Master
A lever or push which overrides (or 'masters') a complete preset, or group within a preset or selected memory.
Memory
Lighting control systems where channel intensities for each cue are filed automatically in an electronic store.
Multiplexing
Passing control instructions, particularly to dimmers or remotely focusable lights, by sending all information in digital format along a single pair of screened wires.

P

Pan
Horizontal (left/right) movement of an instrument.
Parcan
The simple instrument which holds a par lamp and therefore does not require any optical system of lenses or reflectors.
Par Lamp
A sealed beam lamp with the filament contained within the same glass envelope as an optical system producing a near parallel beam.
Patching
A sort of central 'telephone exchange' where channels can be connected to dimmers and/or dimmers connected to socket outlets.
PC [Plano Convex] Spotlight
A lens with one flat surface and one curved surface. This 'PC' lens and the fresnel lens are the alternatives normally used in stage spotlights.
Pipe ends
Spotlights on the ends of lighting bars, crosslighting to model dancer's bodies.
Playback
The part of a memory system where memorised lighting states are recalled to control the light on stage via master levers or pushes.
Practical
Light fitting which is not merely decorative but is wired to light up.
Preset
Anything which is positioned in advance of its being required --such as props placed on the stage before the performance. A control system where each channel has more than one lever to allow intensity levels to be set (i.e. preset) in advance of a cue.
Profile Spot
A spotlight which projects the outline (i.e. the profile) of any chosen shape and with any desired degree of hardness/softness.
Profiled Cue
Lighting change where the rates of increasing and decreasing intensities accelerate or decelerate during the progress of the change.

R

Rating
The maximum and minimum power in kilowatts that can be controlled by a circuit or dimmer channel.
Record
Plotting a cue state by filing it in the electronic data storage of a memory board.
Resistance dimmer
An older mechanical form of dimmer which reduces the flow of electricity to a light by progressively converting the surplus into heat.
Rigger's control
A remote portable hand-held control unit which allows channels or groups to be switched from the stage for focusing when the control room is unmanned.

S

Scatter
Low intensity light cast outside the main beam of an instrument.
Scrollers
Colour changer where a roll of filters are taped together and positioned by a very fast motor activated by digital signals from a control system which includes a memory facility.
Shin Busters
Low level lights at stage floor level, used mainly for dance.
Sightlines
Lines drawn on plan and section to indicate limits of audience vision from extreme seats, including side seats, front and back rows, and seats in galleries.
Silks
Diffusion filters which stretch the light in a chosen direction.
Spigot
An adapter screwed to the hanging bolt of an instrument to enable it to be mounted on a floor stand.
Spill
Stray or scatter light outside the main beam.
Spotlight
An instrument giving control of the angle of the emerging light beam and therefore of the size of area lit.
Strobe
Device giving a fast series of very short light flashes under which action appears to be frozen.

T

Theatre-in-the-Round
A form of staging where the audience totally encircle the acting area.
Throw
Distance between a light and the actor or object being lit.
Thrust
Form of stage which projects into the auditorium so that the audience are seated on at least two sides.
Tilt
Vertical (up/down) movement of an instrument.
Tungsten lamps
Older type of lamps (the stage types are high wattage versions of standard domestic lamps) whose tungsten filaments gradually lose the brightness of their light output.
Tungsten halogen lamps
Newer lamps (now virtually standard in professional theatre) which maintain their initial brightness of light output throughout life.

U

Upstage
The part of the stage furthest from the audience.
UV
Ultra violet light (from which harmful radiation have been filtered out) used to light specially treated materials which fluoresce in an otherwise blackened stage.

V

Variable bean profile
Profile spotlight using a type of zoom (q.v.) arrangement where the differential movement of two lens allows wide variations in both beam size and quality.

W

Wattage
The power of consumption of a lamp, or the maximum available power from a dimmer. A kilowatt is 1,000 watts.
Ways
The number of channels in a control system.

Z

Zoom
A differential movement of two lenses in an optical system. In a simple zoom, the lenses are moved independently, but in more complex forms a single movement alters the size of the beam while the image remains in constant focus. Used in advanced profile spots and scene projectors.

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