Glossary of Lighting Terms

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Absorption filter
A filter which transmits selected wavelengths. The absorbed energy is converted to heat which raises the temperature of the filter.

ACB (see Arc)
Automatic circuit breaker.

Acting area
That portion of a stage used by the actors during a performance.

Adaptor
A short length of cable with one type of plug and a different type receptacle.

Additive color mixing
The creation of colors by superimposing red, green and blue light (which is why it is often called the RGB or red/green/blue color model). The intensities of red, green and blue light determine the resulting color. This method is commonly used in TVs and projection

AF1000
A high powered xenon strobe manufactured by Lightwave Research.

Admedium
Half way between a medium and a mogul screw base.

Ambient light
General background light.

American National Standards Institute (ANSI)
An independent association that establishes standards to promote consistency and interchangeability among manufacturers. This organization was formerly known as the United States of America Standards Institute (USASI or ASI) and previously as the American Standards Association (ASA).

Ampacity
Amperage capacity.

Anode
A negative electrode.

Arc (see ACB)
A brilliant light formed when a break is made in an electric circuit automatic circuit breaker (ACB) A thermal sensitive unit that extin- guishes an overheated lamp.

Arc light
A luminaire using a carbon arc discharge as the source of illumination.

Aspect ratio
The ratio of the width to the height of any imaging system. Generally refers to the final picture on the television or film screen. Nearly always expressed with the height as 'unity'.

Automation
The ability of a piece of equipment to go to predetermined operational points by means of a closed loop servo system without the need for human intervention. Often confused with 'power assisted systems'.

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Baby
A fixture containing either a 500-, 750-, or 1000-watt lamp background light Any fixture used to illuminate walls, flats, scenery, etc.

Backing
Scenery used behind sets to limit the view of the audience or a camera through openings such as doorways or windows.

Backing lighting
The illumination provided for scenery and backcloths.

Back light
A luminaire used to light the subject from the rear to help separation from backings and to increase the three-dimensional effect.

Ballast
The electrical device, required for all discharge lamps, that limits current through the lamp. Additional functions may be incorporated in the basic unit such as starting circuits and dimming control.

Barndoor
Opaque panels (usually four, but sometimes two) that are used to screen light from an area on a set or from the camera lens.

Barrel (Colloq. Bar)
A metal tube, generally 48 mm diameter, for suspending luminaires or scenery. Usually manufactured from steel or aluminum.

Base light
The basic intensity of 'soft' lighting required to satisfy the minimum viewing or technical requirements.

Bayonet base
A lamp base with two prongs (called bayonets) on the rim.

Batten (a)
Horizontal pipe on which luminaires or scenery can be hung; (b) Compartmented multicolor floodlight unit for theatrical lighting.

Beam
The unidirectional flow of total light output from a source, usually a luminaire.

Beam angle
Those points on the light output curve which are 50% of maximum output. The included angle between these two points is the beam angle. Sometimes referred to as the 'half peak angle'.

Beam light
Lensless luminaire with a parabolic reflector to give a parallel light beam.

Beam Shaping
Original method invented by Lightwave Research, beam shaping is a unique feature of the Studio Color® fixture that allows you to align the beam horizontally or vertically. Beam shaping (along with one other special effect) is controlled by the Lens 1 and Lens 2 constructs.

Bipost base
A lamp base with two long metal contacts.

Blackening
"Boiloff" of the tungsten from the filament that adheres to the inside of a tungsten-standard bulb.

Blackbody
A body which, completely absorbs any heat or light radiation falling upon it.

Blackbody radiation
Radiation that comes from an ideal blackbody. The distribution of energy is dependent only on the temperature of the blackbody and is governed by Planck's radiation law.

Blackout
To switch off all illumination (except exit lights).

Blackout switch
A master on/off switch used for controlling the overall production lighting for either stage or studios.

Blade
A small narrow flag that may either be opaque, net, or of diffuse material.

Blister
A swelling of a small part of a bulb.

Block control
Cyberlight® is a good example of a block-controlled fixture; that is, you do not control it using an arbitrary DMX starting channel per se, but rather at a channel boundary. There are two channel boundaries you can select: 15-channel and 20-channel. If you choose to control your Cyberlight on a 20-channel boundary, for example, each fixture takes up a contiguous block of 20 DMX channels.

"Booster"
A filter that raises the color temperature of a light source.

Bounce lighting
Directing light onto a large diffuse surface to produce a soft reflected light.

Brail
To pull a lighting suspension or piece of scenery out of its normal hanging position by means of attached rope lines.

Bridge
A narrow platform suspended over the acting area. Luminaires and projection devices mounted on the bridge are accessible during performance.

Brightness
(See Luminance.)

Brightness ratio
Ratio of maximum-to-minimum luminances occurring within a scene.

British Standards Institute (BSI)
Produces technical specifications and other documents which are made generally available. The main aim of the Institute is to maintain standards, quality and safety in goods and products.

Broad
An open-face fixture that utilizes the soft illumination of its lamp [as opposed to indirect illumination (see softlite) on a subject] - a wide-angle floodlight..

Bump (button action)
Turns on a Preset as long as the button is held down. Dim instantly goes to 100% regardless of fader position.

Butterfly
A large scrim measuring not less than 4 x 4 feet (1.22 x 1.22 meters).

Brute
A 225 Ampere D.C. high intensity carbon spotlight with a 24 inch diameter Fresnel lens.

Bubble
Slang term used in the television and film industries to describe lamps of any type.

Bulb
An old term describing the bulbous glass envelope of an electric lamp.

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C
Symbol for coiled filament.

Cathode
A positive electrode.

CC
Symbol for coiled-coil filament.

'C' Clamp
(See Hook clamp.)

Camera light
A luminaire mounted on a camera for lighting along or near the optical axis, usually to provide catch lights for the subject's eyes.

Candela
Unit of luminous intensity.

Candlepower
A term that was used for intensity but has been replaced by the candela.

Carbon arc
A DC arc source in which the arc is produced in air between a pair of carbon electrodes. These electrodes burn away and must be advanced during operation.

CD
Compact disc containing digital audio information.

CD ROM
Compact disc read-only memory. Disc or disc drive containing digital information. Typically installed in computer. Cue Lists support audio CD ROM input.

Color mixing
Process of creating colors using either the RGB or HSI color models.

Color Pro®
A color changing luminaire manufactured by Lightwave Research.

Channel
The circuit from the fader on the lighting control console to its associated dimmer.

Chaser lights
A linear string of lamps wired and controlled so that the lights appear to be following in sequence.

Chroma
In television, the information which gives the color of the image as distinct from its luminance (brightness).

Chromakey
A television.special effect which uses a monochromatic colored background to allow electronic switching to another picture. Deep blue is commonly used for the background when the foreground involves people.

Chromaticity
The color of light, as defined by its chromaticity co-ordinates, generally using the CIE diagram.

Circuit breaker
An electrical switch positioned in the circuit that will automatically operate to break the flow of current under abnormal conditions.

Cold mirror
A dichroic coated glass surface which reflects visible light but allows infra-red energy to pass through the reflector so that the reflected light contains less heat.

Color
A sensation of light induced in the eye by electromagnetic waves of a certain frequency - the color being determined by that frequency.

Color frame
A frame used to support color media at the front of the luminaire.

Color media
Any colored transparent material that can be placed in front of a luminaire, often referred to as 'gels' (for gelatin). Glass and other plastic materials are also used.

Color rendering index (Ra)
The evaluation of the effect of a light source on a set of colored test pieces representing portions of the visible spectrum. The higher the index towards its maximum of '100' the better the color reproduction. Sources in general require an index greater than 90 to prevent noticeable color distortion.

Color temperature
A term used to describe the balance or content of each spectral component of white light. Color temperature, in turn, relies on the concept of the black body.
A black body is a theoretical object that absorbs all of the energy that contacts it. Heating a black body causes it to emit radiation. When the spectral composition of a black body matches the spectral composition of a white light source, the temperature of the black body (in degrees Kelvin) is the color temperature of the light source.
For example, a light source that is rated at 5600° Kelvin (such as the light source used in Cyberlight) matches the radiation of a black body heated to 5600° Kelvin (9620° F).
Because not all light sources exhibit a smooth spectral power distribution in reality, color temperature is an approximate measure of a lamp's spectral output.

Color wheel
A circular mechanism holding several different colors mounted in front of a luminaire which can be rotated by hand or by a motor drive.

Complementary colors
A pair of colors in the additive color mixing system which combine to make white light.

Condenser
A lens or mirror used in an optical system to collect the light being radiated from a source, which is then directed onto the gate of the projection system.

Contactor
Large electrical switch used within the input electrical system to control the on/off state of the supply. Usually operated by an electromagnetic coil.

Contrast range
This is the ratio of the brightness between the lightest and darkest areas in a subject. In a video system, it is the range between the maximum signal which can be satisfactorily handled without distortion and the acceptable electronic noise level of the system.

Correlated color temperature (CCT)
Many sources of light energy do not have the same characteristics as blackbody radiators, but sources which have a mainly white light output can be given a correlated color temperature. This is defined as that temperature of the blackbody radiator which most closely matches that of the light source in question. It therefore gives a rough guide to the blueness or redness of the source.

Cosine law
The equation which allows the calculation of illumination on a surface which is at an angle to the incident light.

Counterweight system
Mechanical system for flying scenery in which the weight of the pieces of scenery is balanced by adjustable weights in a cradle running up and down in guides in a frame normally at the side of the stage. The system is also used for lighting bars.

Cross barrel
Used between barrels to allow accurate positioning of luminaires.

Cross fade
A lighting change where one set of channels reduces in light intensity and another set increases in light intensity.

Crosslighting
Illumination from two luminaires at approximately 180#&176; to each other on opposite sides of the subject. They are generally hard sources.

CSI
A discharge lamp which approximates to sunlight for color balance (CCT 4000 K).

Cue
A signal, which may be written, verbal or by action, that causes motivation of artistes or technical staff.

CueList
A CueList is a series of cues (events) available for playback on demand. CueLists allow the user to conveniently run through an entire show by simply pressing one button or automate an entire show with internal or external synchronization. Multiple devices can be simultaneously controlled with CueLists. Unlike Scenes and Sequences, CueLists reference songs and have the ability to accept and output MIDI data. CueLists play back the Presets that are stored in Songs.

Cyclorama
A backing, mounted in the studio, to provide a continuous surface and an illusion of infinity.

Cyclorama (cyc) lights
Luminaires with specially designed reflectors used either at the base or at the top of cycloramas to light in a smooth manner.

Cyberlight®
An automated moving mirror luminaire manufactured by Lightwave Research.

CYM color mixing
Another name for subtractive color mixing.

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Data cable
Cable providing data to fixtures. Most typically in a daisy chain (one fixture to another fixture which then passes the signal to another fixture, et al. and configuration.

Daylight filter (a)
A blue filter used to change the color of a light source from tungsten at 3200 K to approximately 5600 K; (b) A blue filter used on a camera to allow daylight balanced film stock to be used with tungsten lighting.

Desk
A synonym for a lighting console.

Devitrification
The process which causes a change from a 'glassy' state to a crystalline state.

Dialog box
Dialog box displays are displayed to request information about the task you are performing or to present you with information.

Dichroic
A dichroic (from Greek, meaning "two-color") filter achieves a richly-saturated color without using any pigmented (colored) materials. In simple terms, it achieves this effect by either reflecting or "cancelling out" through destructive interference all but a narrow range of the light spectrum.
The "dichroic" name refers to the fact that one color (or broad range of colors) is reflected or cancelled out, and one color(or narrow range of colors) is transmitted through the dichroic filter.
The dichroics used in Cyberlight are all manufactured at the High End Systems Optical Coating and Assembly Laboratory in Austin, Texas. They are made from a base of Pyrex®-like glass material coated with multiple, microscopic layers of specialized materials separated by junctions that either transmit or reflect certain wavelengths of light, accounting for the resulting color.
Dichroic filters offer a number of advantages over traditional gel filters: since they are made of Pyrex-like glass and absorb almost no heat themselves, they theoretically have no failure mechanism; they transmit more light than gels; and their resultant colors are more richly-saturated than is possible with a gel.
Dichroics are currently used for all Cyberlight colored lithos, color mixing flags, effects and of course the color wheel dichroic filters.
(Dichroics and lithos are also used on other High End Systems fixtures.)

Diffusor
Sheets of frosted plastic or spun glass fiber used to soften the shadows produced by the light beam.

Diffusion
Diffusion is a special effect that causes a defined spot with a soft edge similar to a FRESNEL. That is, the edges of the pattern go out of focus.

Dim
The brightness of light emitted by a given fixture. Gradual dimming is usually controlled by a mechanical iris, as opposed to a shutter, which is used for quick blackouts as well as strobing.

Dimmer
An electronic device which controls the amount of electricity passed to the lamp of a luminaire thus controlling brightness.

Dimmer
An electronic device used to reduce current flow to a lamp and therefore allow its light intensity to be adjusted.

Dimmer curve
A graph which shows the light output or voltage output of a dimmer against the channel control setting.

Dimmer room
The area allocated for the equipment racks which contain the dimmers and associated equipment.

Discharge sources
Light produced by the passage of electricity, through a gas, across two electrodes enclosed in a quartz envelope, e.g. Xenon, CSI, HMI, MSR lamps.

Disk
An apparatus for storing and retrieving data.

Diskettes
Typically a 3.5 inch magnetic floppy disk is used to transfer files between Personal Computers.

DMX 512 control protocol
DMX 512 is a standard method of controlling lighting fixtures and other devices (such as lasers and hazers). Developed by the United States Institute of Theatre Technology (USITT), DMX 512 is supported by leading entertainment industry equipment manufacturers, such as High End Systems.
DMX 512 (D for digital, MX for multiplex and 512 is the number of channels per link) is a reliable, efficient and well-understood method of controlling lighting devices. Its strength lies in its ability to control virtually any mix of DMX-compatible devices on the same link using a single DMX-compatible controller.

DMX channel
The DMX 512 protocol allows a total of 512 channels to be used on a particular link. (A link is a group of devices connected on a daisy-chain of XLR cabling.) You need to assign a unique starting channel to each Cyberlight you wish to respond independently to control commands. Multiple fixtures may be assigned the same channel if you wish them all to respond to control commands in the same way.

Double broad
This is a twin lamp floodlight generally used on studio floors as a local filler.

Double purchase
A suspension system used on counterweight bars which gears the movement of the counterweight bucket to half that of the bar itself. (See Single purchase.)

DOS
Disk operating system first developed by by Microsoft® Corp. Basic operational control for many computers.

Douser
A small metal flag used in follow spots to cut off the light beam without having to switch off the electrical supply to the source.

Downlighter
Usually refers to small ceiling mounted luminaires in control areas.

Downstage
The stage or studio area which is nearest the audience.

Drop arm
A device used to hang a luminaire lower than the normal suspension system permits.

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Effects projector
A focusing luminaire used to project slides or shapes. The effects can also be motor driven.

Efficacy
This is the efficiency of a light source in converting the electrical input power to light and is expressed in 'lumens per watt'.

Efficiency
This is a measure of the useful light output in lumens against the total lumens generated by the light source.

Eggcrate
A device consisting of small cross baffle plates to restrict the spread of the light beam on a softlight.

Ellipsoidal spotlight (profile projector)
A luminaire which uses an ellipsoidal reflector and a reasonable quality optical system to project shapes and patterns with a hard edge.

Extension bar
This is used to extend lighting barrels for accurate positioning of luminaires.

Excluded Memory Address
Physical areas of RAM excluded from the operating system and reserved for execution of other tasks than system operation.

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Fader
A control device for indirectly setting the current output of a dimmer and thus varying the light intensity. Originally were levers, but are often wheels in modern lighting control systems.

Fader Presets
Use of Fader Presets controls the playback of Scenes and Sequences. In Status Cue® each of the 16 Fader Presets may have its own output. Thus, you can layer the Fader Presets to build effects.

Field angle
Those points on the light output curve which are 10% of maximum output. The included angle between these two points is the field angle.

Filler Light
used to control shade areas. Usually a softlight but can be controlled hard light.

Film speed
(a) A measure of the film's sensitivity to light expressed in numerical terms to give an 'exposure index' which is used in the ISO and ASA system on light meters; (b) The velocity of film passing through movie cameras or projectors is measured in frames per second or in meters per minute.

Firmware
Software used by an automated light fixture's microprocessors to control its functions. New firmware can be uploaded to Cyberlight using either the LinkCard or the Cyberlight Upload Module.

Five K
A colloquial term for a five kilowatt spotlight.

Fixture
A generic term for a lighting device or luminaire. The terms fixture and luminaire are used interchangeably.

Fixture Number
A unique number that you assign to each fixture connected to the controller. You use the fixture number to program each fixture uniquely. More than one fixture can be assigned to the same address as long as you want those fixtures to respond to the same set of constructs in exactly the same way.
The expression "Fixture number" is featured in the LWR protocol control scheme, rather than the expression "Starting channel" which is used by DMX protocol.

Flag
A sheet of metal or card mounted a short distance in front of the luminaire to give a sharp cut off to the light beam.

Flip
A special function for moving yoke fixtures, such as Studio Color. The unit pans 180°and tilts to the opposite position of the 90°(straight down) axis. This allows more physical movement before a stop is reached.

Flood
By focusing a lamp close to a lens, the diameter of the light beam is enlarged and thus gives the widest field of illumination.

Floodlight
A luminaire which has only a reflector to control the beam and has wide angle distribution. (See Softlight and Cyclorama light.)

Floor controller
Any controller (flag, net, diffusion) that is placed in a gobo stand on the stage floor and used to intercept light rays.

Fluorescence
The ability of some materials to convert ultraviolet energy into visible light. (alt) Light caused by radiation of a phosphor coating.

Fluorescent filter
Any one of a family of filters used to convert light to a continuous spectrum.

Fly
To suspend scenery or equipment above a stage or studio floor by means of a suspension system which can be manually operated or driven by motorized units.

Fly gallery
The gallery which extends around the side walls of the stage area approximately 10m above the stage floor. It is used for operating the ropes which adjust the counterweight system and hence the height of the bars above the stage.

Fly tower
The upper part of the stage area which is formed as a tower, usually with galleries, to suspend scenery out of sight of the audience.

f-number
A set of numbers used to express the aperture of a lens which represents its light transmission. It is worked out by dividing the focal length of the lens by the diameter of the opening in the lens diaphragm. It is also colloquially known as the 'stop'.

Focal length
The distance of the focal point from the lens is called the focal length of the lens.

Focal point
The point where the incident parallel rays, which are bent by a lens, meet in focus.

Focus
In optics, the adjustment to give a clearly defined image. Used in the lighting industry to indicate the process of 'spotting' or 'flooding' the light beam of a luminaire. When used in the sense of sophisticated automated lighting fixtures, focus is a variable Construct that allows you to remotely bring the projected beam and gobo image in and out of focus.

Follow spot
A narrow angle, focusing hard edged spotlight used to follow moving artistes.

Footcandle
An old unit, now superseded by 'lux', used to describe illumination which was measured in 'lumens per square foot'. (alt) A measurement of incident light falling on a subject at a specific point; 10.8 lux.

Footlambert
The old unit for luminance (brightness) which has been replaced by the 'nit'.

Footlights
Lights mounted along the edge of a stage to provide uplighting.

Frame
Plywood with cutout designs that throw patterns across the set (such as large windows, prison bars, etc.).

Framing shutters
Opaque panels inside an ellipsoidal fixture that intercept the light beam and produce a hard-line cutoff to a circular pattern.

Fresnel lens
A plano-convex lens with the convex surface "flattened" into concentric rings that collect and direct scattered light into parallel rays.

Fresnel spotlight (colloq. Fresnel)
Luminaires fitted with Fresnel lenses of varying sizes; the width of the beam can be changed by varying the spacing between the lens and the lamp/reflector assembly.

Front of house lights (FOH)
Luminaires usually mounted on barrels, and generally concealed, above the audience seats.

Frost
When used in the sense of sophisticated automated lighting fixtures, frost is a variable construct effect that typically allows you to add a haze or fog effect in increasing/decreasing densities to the projected pattern. (alt) Translucent gel or plastic used to diffuse light sources.

Fuse
A protective device for electrical circuits; originally a piece of special wire but nowadays nearly always a metal link contained in a ceramic cartridge.

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Gaffer
Term used in the film industry to describe the chief technician.

Gate
The optical center of a profile projector where the shutters are positioned and an iris or 'gobo' can be inserted.

Gelatin (Gel )
A thin sheet of collagen that has been dyed (See Color media.).

Glass filter
Optically flat glass that is either impregnated or coated with a filter dye; a gelatin filter that is sandwiched between two pieces of optical flat glass.

Gobo
A mask placed in the gate of a profile spot to shape the beam. It is a simple form of outline projection. (alt) Any opaque unit used to eliminate light from a particular area; a "go-between". In Photography GOBO is an acronym for 'Goes Before Objective'

Gobo indexing
Gobo indexing is the process of positioning a rotating gobo in a static position anywhere through 360 degrees in 1/4 degree increments (typically)

Gooseneck
A flexible shaft with a clamp at one end for securing to a post, fixture stand, yoke, etc.; the other end contains a small thumbscrew in which to tighten down small flags, scrims, dots, targets, etc.

Grid
A network of uniformly spaced horizontal and perpendicular pipes in a video studio from which fixtures are hung; an integral unit of a studio arc that reduces input current of 120 volts to 73 volts across the electrode gap (See Lighting grid).

Groundrow
Compartmented lighting units usually arranged in linear fashion for lighting from the base of cyclorama.

Group
Group is an automated lighting term meaning that a number of fixtures are operated together as a group by a control device.

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H
Lighting manufacturers' code for mercury.

Half scrim
A semicircular scrim used to attenuate part of the light beam. (See Scrim.)

Hard glass halogen lamp
A tungsten halogen lamp with an envelope of borosilicate glass.

Hardlight
A luminaire that produces well-defined shadows, normally a spotlight.

Heat filter
A light filter which removes infra-red from the beam to reduce heat from the source of illumination.

Hertz (Hz)
The unit of frequency which is measured in cycles per second. Other units are kilohertz (kHz) and megahertz (Mhz).

HID
High-Intensity Discharge; a type of lamp.

High key
Describes a scene containing mainly light tones well illuminated without large areas of strong shadow.

HMI (also CID and MSR)
Discharge lamps which have a daylight color balance (5600 K). (alt HMI) A mercury, metal-halide, iodide lamp with a multiline spectrum housing The metal portion of a fixture that covers the light source, socket, and reflector.

Hoist (See Winch)
Old term used to describe either manual or motorized lifting equipment.

Homing
A function of a fixture that returns its constructs to known or default states (defined as their home positions). Most automated lighting fixtures are automatically designed to home all effects, etc. when they are first switched on.

Hook clamp
A clamp used for suspending luminares from lighting bars.

Hot mirror
(Also called infrared filter or heat filter). Dichroic glass placed over the opening of the reflector. Its purpose is to eliminate infrared and ultraviolet wavelengths, both of which fall far outside the visible light spectrum; therefore, light output is not affected. It also helps prevent heat buildup inside the fixture.

HSI (Hue, Saturation, and Intensity)
HSI is a model for mixing colors based on saturation and intensity.
Hue- the color attribute that distinguish one color from another.
Saturation- the percentage or amount of gray in a color. Increasing saturation lowers the amount of gray in the color, and decreasing saturation increases the amount of gray in the color.
Intensity (or brightness)- the difference in the light intensity transmitted through a color (independent of hue and saturation).

HTP
Highest Takes Precedence. Used primarily for dimmer packs and some Lighting desks where the highest dim constructs take precedence over lower dim constructs.

House electrician
An electrician permanently employed by a theatre or concert hall to maintain and operate the electrical equipment in the premises.

House lights
A lighting system permanently installed to either illuminate an audience area or provide worklights in studios.

Hue
The quality by which one color is distinguished from another as a result of their wavelengths. It does not take into account the brightness or intensity of the color.

Hybrid spectrum
A continuous spectrum dominated by a line spectrum.

Hydragryrum
The Greek work for mercury
Lighting manufacturers code for iodides; also the symbol for intensity.

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Illumination
The luminous flux falling on unit area of a surface. The unit of illumination is the lux (1 lumen per square meter) and it is the measure of the quantity of incident light.

Incandescence
The emission of light by raising a material to a high temperature. (alt) The glowing of a body due to its higher temperature; a reference to the glow from a filament lamp.

Indexing
The process of turning or rotating a projected pattern or picture into the desired viewing position. This position is then typically memorized by software so that if the fixture (or mirror) is moved the gobo turns in the appropriate direction to compensate for the fixture's (or mirror's) movement. E.g. if the gobo is indexed and memorized in the upright position it will maintain that position irrespective of the changes in fixture (or mirror) position.

Indirect
Light that is reflected from a surface before it falls on a subject

Infrared
Long wavelengths invisible to the eye.

Inkie
A 100-watt fixture with a fresnel lens.

Instant Presets
Instant Presets provide you with a mechanism to instantly playback entire Scenes and Sequences that were previously assigned as an Instant Preset.

Intellabeam®
An automated moving mirror luminaire manufactured by Lightwave Research.

Insulation
A non-conducting material (rubber, neoprene, etc.) used to cover current-carrying wire.

Intensity
The light-giving power of a source.

Interference filter
A filter that disrupts wavelengths, causing them to "cancel out".

Internal reflector
An integral reflector formed on the inner rear surface of the envelope of a lamp and is usually parabolic or elliptic in shape.

Inverse square law
The equation which is used to calculate the illumination at a given distance from a source of light.

Iris
A series of adjustable metal plates arranged to give a variable circular aperture. Used in lighting projectors to alter the size of the light beam.

IRQ - Interrupt Request
When an option (device) needs to be serviced by the computer it sends out an interrupt request on its assigned level to get the computer's attention. The computer then responds with an interrupt service routine. The computer services the interrupts in order of priority. That is, a higher priority interrupt is serviced before a lower priority. Interrupts are organized into a multi-level priority scheme, but generally, the lower the IRQ number the higher the priority. Timers, keyboards, serial ports, disk controllers, printer ports, mice, LinkCards, and so on, all use interrupts.

Iris (aperture)
The iris is a device with a variable circular opening that controls the beam diameter and amount of light emitted from a fixture.

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Jacket
Rubber or neoprene covering on a cable; an additional glass covering that either protects the lamp from the weather or halts the lamp's ultraviolet rays.

"Juice"
Electricity.

Junior
A 2000-watt fixture with a fresnel lens.

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K Electricity:
The math symbol for 1000.
Color Temperature: The symbol for Kelvin, a scale that compares the visible aspects of a light source to a heated body.

Kelvin
The SI unit of thermodynamic temperature. It uses the same size of degree as the Celsius scale. (Zero K = - 273°C.)

Key light
The principal modeling light, usually a spotlight.

Kicker
Generally a hard light source used to provide obvious highlights. (alt) A type of back light that is used to apply a Rim light to an actor's face.

Kilowatt
Electrical power term for 1000 watts.

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Lamp
A glass or quartz envelope which contains filaments or electrodes. The term lamp is often used to describe a luminaire, which is to be avoided as it can cause confusion. (Colloquial terms include globe, bubble, source.)

Lamp strikes
The number of times the lamp has been illuminated. Once the lamp is "switched on", whether it is illuminated continuously for one second or one minute, it counts as one strike.

Lampholder
A unit that accepts the base of a fluorescent lamp.

Lantern
(See Luminaire.)

Leaker
A lamp in which the seal has been broken and air has entered.

LD
Abbreviation for lighting designer or lighting director.

Leko
A slang term used in America to describe ellipsoidal spotlights.

Life
Usually refers to the manufacturer's rates life in hours of a lamp at its normal voltage and is based on the average life of a number of lamps which have been tested.

Light center length (LCL)
The distance from the center of the filament to a standard point at the base of the lamp. (the reference point varies depending on the type of lamp).

Lighting batten
A barrel assembly with integral power feeders for luminaries.

Lighting control console
A unit which contains the controls for adjusting the channel levels and thus the dimmer outputs, 'group channel' control, memory control, playback system and special effects.

Lighting designer (director)
The person who creates and implements the lighting design for a production.

Lighting grid
In television a structure mounted at high level above the operational area, usually made from steel or aluminum or a combination of the two, for the purposes of suspending luminaries and ancillary lighting equipment. In theatre, it is the framework above the stage in a close gridiron formation to allow operators access for positioning lights and scenery.

Lighting plot
A scale drawing which shows the disposition of the lighting equipment in relation to the production concerned. Used by the LD and electricians.

Lighting ratio
The relationship of key light plus fill light to the fill light alone.

Light source
An emitter of light (sun, sky, lamp, arc, etc.).

Limbo
Describes a state of lighting where the background details are suppressed. In television this is usually created by 'blackness' whereas the film industry tends to use a white background.

Linear filament
A filament that extends the length of the bulb.

Line spectrum
A spectrum divided sharply into defined wavelengths.

Linnebach projector
A lighting unit, basically a box without a lens, which contains a small point source of illumination to project soft diffused images of cutouts or glass slides.

Lightwave Show Control (LWR)
Used with Lightwave Control Center software.
The default control protocol for Cyberlight, LWR allows you to control up to 8 independently-operating fixtures per link with the Cyberlight LCD controller or up to 16 independently-operating fixtures per link with Status Cue. LWR protocol is also used to perform firmware uploads using a High End Systems LinkCard or the Cyberlight Upload Module.

Link
(Also called daisy chain.) A DMX 512 link is a logical bus (serial) connection between devices. A link can connect one controller to many fixtures, or it can interconnect controllers via their Master and Slave ports.
Each DMX 512 link can have up to 32 devices or span 500 ft (153 m). A serial data distributor must be used to extend any link beyond those limits.

Litho
A litho has a pattern etched on it (some lithos are also textured), as the name "LithoPatterns" suggests. All LithoPatterns® are designed and manufactured at the High End Systems dichroic lab in Austin, Texas. There are currently a large number of available lithos, including LithoPatterns, Art Glass, Fusion Fire, PsyDye, PsyDye Special Effects, PsySpin and Special Effects.
A dichroic process is used to color all High End System's LithoPatterns.

Littlites®
Small halogen lamped gooseneck illuminator made by Littlelite Corp., that has become a standard within the entertainment industry.
Two dimmable Littlites® are provided with each High End Systems Status Cue® Console.

Loop
A sequence or series of programmed pages that repeats continuously until you stop it.

Louvres
Thin black metallic strips located on a luminaire to reduce spill light. (See Egg crate.) When fitted in front of a luminaire may also be adjustable at various angles to provide dimming without color change.

Low key
Describes a scene containing mostly dark tones with large areas of shadow and is often used to create a dramatic mood. (alt) A manner of illumination in which detail in the shadows is subdued or obscured completely; also high-contrast lighting predominated by shadows.

Lumen
An amount of light energy within an area. The lumen is the unit of 'luminous flux' and is defined as the amount of light which falls on one square meter of a surface at a constant distance of one meter from a source of one candela.

Lumens per watt
The light output in lumens produced by a source for each watt of electrical power supplied to the source.

Luminaire
A general term for a complete lighting unit. It includes the housing, the reflector, lens and lamps. (Colloquial terms include light, lantern, fixture, unit, instrument, fitting.)

Luminance
The measure of brightness of a surface. It is measured in 'Nits'. The old unit was the 'foot lambert'.

Luminous flux
The transfer of energy in the visible wavelength range lux The metric measurement relating to incident light that falls on a subject (10.8 lux = 1 foot-candle).

Luminous intensity
A measure of the energy from a light source emitted in a particular direction. It is measured in candelas.

Lux
The unit of luminance (illumination). It is the unit of measurement for the incident light arriving at a surface. The old measuring system used foot-candles. (One foot-candle equals 10.76 lux.)

LWR Protocol (LWR)
The native control protocol for Cyberlight, Intellabeam, and Trackspot. LWR protocol offers all the features of DMX-512 plus a checksum routine for data verification.

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MacBeth
A deep blue glass filter that converts tungsten light to a color temperature compatible to daylight.

Master fader/dim
The Master fader or dimmer (grand master) control typically provides live master dim control over all connected lighting fixtures.

MCB
Miniature circuit breaker.

MCCB
Molded case circuit breaker.

Master/group master
Usually refers to a lighting control system fader which overrides by electrical means a group of individual faders.

Maximum overall length (MOL)
The overall physical length of a lamp including all electrical contacts.

Memory
The term used to denote 'filed' information which controls the lighting channels.

Mickey
A 1000-watt open-face fixture.

Microphony
The interference caused by the mechanical vibration of any electrode system. Particularly troublesome on the older type of camera pickup tube, such as the Image Orthicon and the Plumb icon tubes used in color cameras.

Midget
A 200-watt fixture with fresnel lens.

MIDI
MIDI (Musical Instrument Digital Interface). As well as being the internationally agreed common control protocol for musical instruments, MIDI is also the communication protocol for many microprocessor-based lighting devices.

MIDI Show Control (MSC)
A control protocol (language) that allows a variety of different types of devices to be controlled from a central source, such as a lighting console.

MIDI Time Code (MTC)
A timing protocol that allows synchronization between MIDI devices.

Mighty
A 2000-watt open-face fixture.

Mini
A 200-watt fixture with fresnel lens, smaller than a midget.

Mirror ball
A motor driven ball with its surface covered in small mirrors. When rotated, with spotlights shining to it, it produces moving points of light.

Miscellaneous light
Any fixture used to illuminate a special item.

Mixed
A surface that reflects specular and diffuse rays.

Modeling light
The term is used to describe any luminaire, generally a hard source, that reveals the depth, shade and texture of subjects.

Modifier
The general reference to a unit that has an effect on the intensity or character of a light ray.

Module
A fixture with a single lamp and its own switch that is clustered with other units of the same type and is worked singly or as part of a group.

Mogul base
A lamp base larger than standard residential size.

Monochromatic
Seeing in gradations of one particular color only.

MSpeed (movement speed)
This Construct defines whether the fixture's pan/tilt, colors or gobos (static and rotating) change at mirror movement speed (MSpeed) or at full speed. The speed settings determine how long it takes for the selected fixtures to reach their programmed position in the Scene or Sequence. MSpeed is user assigned to the Color, Gobo, or Rotating Gobo Construct.

Monitor
Video display terminal for a computer system.

Mouse
The mouse is the most common type of pointing device used on personal computers. Another common pointing device is the trackball which is used on Status Cue. These devices allow you to move the pointer (or cursor) around the screen, create drawings, select menu items, and so on.

MSR/MSD
MSR stands for Medium Source Rare Earth and describes the family of arc lamps used in Cyberlight. Rare earth elements (such as Dysprosium and Holmium) are added to metal halide to give the lamp a more continuous spectrum.
MSD stands for Medium Source Daylight. ("Daylight" is a reference to the fact that the lamp has roughly the same color temperature as ordinary sunlight.) The MSD lamp has basically the same composition and the same color temperature as the MSR lamp, but it has a lower light output and longer life.

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Nanometer
A unit of metric measurement equal to one billionth of a meter, which is used to measure light wavelengths.

Net
A cloth material with a hexagonal weave.

Neutral density filter
A filter which attenuates the light passing through it without affecting the color of that light.

Nite-for-nite
The shooting of film or the videocasting of exterior night scenes in the nighttime hours.

Nit
The unit of luminance, which is one candela per square meter of surface radiation. It is therefore the measure of the brightness of a surface.

Non-dim
Describes the circuit which replaces the normal dimmer function, where the circuit is switched 'on' or 'off' only, either by a switch or relay system.

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Objective lens
(See Projection lens.)

Offstage Areas
that are out of the eye line of an audience.

One-and-a-half-K
A 1500-watt open-face fixture.

One-fifty
A 150-amp carbon arc.

One K
A 1000-watt fixture, either open-face or with fresnel lens.

Onstage
In view of the audience.

Opaque
Absorbance of electromagnetic radiation at specific wavelengths, generally refers to the fact that light is not transmitted.

Open-faced luminaire
Describes luminaries with no lens system, such as the 'Redhead'.

Oxidization
An electrochemical "welding" of two different metals

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"paper amps"
An amperage rating given in rounded numbers higher than actual amperage.

PCB
Printed circuit board.

Page
The basic programming unit, consisting of addresses (fixtures), constructs and their parameters (values).

Pan
Term describing the horizontal movement, about a point of luminaries or equipment.

Pantograph
A mechanical cross-armed device for varying the height of luminaries or other fittings. It is generally spring balanced but can be operated by a motor or manually driven gear system.

PAR
Acronym for Parabolic Aluminized Reflector lamp. Size (64, 46, 36 etc.) is measured in 1/8" pitches across the lamp.

Parabolic
A mirror shaped like a parabola that directs a beam in parallel rays.

Par-can
A simple luminaire, basically a metal tube, with a PAR lamp mounted in it. The type of lamp determines the beam spread.

Patch
A term describing the connections made on low voltage control or power systems.

Patch panel
A system rather like an old telephone operator's interconnection system (switchboard) to connect low voltage circuits or high voltage circuits.

PCMCIA, PC Card
PCMCIA stands for Personal Computer Memory Card International Association. The official name of adapters that comply with standards issued by the PCMCIA is now PC Card.

Phosphor
A material that glows when activated (as when struck by electrons).

Pin connector
A connector that is fitted with slender rods of copper on the plug and slender matching shafts on the receptacle.

Pin matrix
A method of coupling control channels into groups by the insertion of special pins into a 'x' and 'y' matrix, where the 'x' axis may represent channels and the 'y' represent groups.

Pitting
The forming of tiny holes on the surface of a base or socket.

Pixel
A picture element. The smallest element of a CCD array. The definition is governed by the number of 'pixels per area', the higher the amount the better the definition.

Plano-convex lens
A lens with one flat surface (piano) and one spherical surface (convex).

Planar filament
A group of filaments arranged in such a manner that they are in one plane (lined up evenly).

Plastic filter
An acetate, polyester, vinyl, or Mylar impregnated with a color.

Playback
That part of a lighting control system where the lighting memories and/or other lighting states are combined and controlled by output master faders or switches.

Plug
The male end of a connector.

Pole operation (Colloq. pole op)
The control of electrical and mechanical functions on luminaries and suspension equipment by means of a long metal pole.

Power
Measured as Watts. Amps (current) multiplied by Volts (electric potential) = Watts.

Power assisted systems
Luminaries and suspension equipment under the direct control of an operator, e.g. winch control motor systems.

Practical
Describes a light, e.g. table lamp, that can be effectively switched on and off by an actor within a scene. In television, the light will usually be remotely switched from the lighting control console.

Prefocus
Denotes special lamp caps so that the filament lines up precisely to the optics of a luminaire.

Preset (blind mode)
A facility on lighting control systems that enables a lighting plot to be set up without affecting the lights already operative.

Primary colors
The primary additive colors are red, green and blue. The primary subtractive colors are cyan, magenta and yellow.

Prime
An open-face fixture whose basic use is a key, kicker, or back light.

Profile spot
A luminaire used to project shapes or patterns.

Projection lens
A lens specially designed to project slides or shapes onto a surface with considerable enlargement of the slide or original material.

Proscenium arch (opening)
The surround to the stage area and through which the audience views the performance.

Prism
Prism is a multi-faceted special effects lens that multiplies the projected pattern according to the number of facets the prism lens possesses.

Programming (automated lighting)
The inputting and recording of automated fixture values to achieve a desired design or theme.

Pup
A colloquial term for a one kilowatt spotlight.

Quartz
Crystalline silica which is glass like and used to make envelopes for lamps. It is generally transparent to ultraviolet radiation.

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Receptacle
The female end of a connector.

Record (or file)
The action of memorizing a lighting state on a lighting control system.

Reflectance (reflection factor)
The ratio of the reflected light to the incident light falling on a surface, measured in lumens.

RGB
RGB (Red, Green, and Blue) is a color model commonly used to mix colors. RGB is a color additive model. That is, when you mix 100 percent of red, green, and blue, the resultant color is white (additive), and mixing 0 percent of the three colors the resultant color is black.
Fixtures often use the subtractive CMY (Cyan, Magenta, and Yellow) color model because 0 percent mix of the three colors yields white. A fixture which has its color flags positioned out of the light path produces white. Status Cue converts the RGB colors to CMY for use with fixtures.

RGB color mixing
Another name for additive color mixing.

"Rifle"
A reflector board with a mirrored-surface that has an intense beam.

Rig
To set up scenery equipment and lighting.

Rigging
Collective term for suspension equipment.

Rigger's control
A remote portable hand-held control unit for controlling either luminaries or winch systems.

Rim light
A type of back light that outlines an actor from head to toe.

Risers
The flat surfaces on the Fresnel lens rings that form the division between segments.

RMS
Abbreviation of root-mean-square. The RMS value of the current is a measure of its effectiveness in producing the same heating effect in a resistance as a direct current. It therefore allows for various wave shapes and directly relates to the power in watts.

Rotating gobos
An effect whereby gobos may be continuously rotated during projection in a forward or reverse direction. Typically the speed of gobo rotation is remotely adjustable.

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S
Lighting manufacturers' code for sodium vapor; also symbol for medium arc or straight filament.

Safety bond (also safety chain)
A short length of wire rope or chain formed into a loop around a suspension point to act as a secondary means of suspension in the event of failure of the primary system.

Saturated rig
A lighting installation where luminaries are installed in sufficient numbers to cover the total acting area without rigging and de-rigging.

Saturation
A term used to describe the density of a color between the pure color concerned and white, i.e. a deep red or pink.

SB
Self-ballasted.

Scattered
A surface that is crinkled, stippled, or creased and reflects light in all directions.

Scene
One static setting or look consisting of selected fixtures, their Constructs, and timing. A Scene may be as simple as a single fixture, in plain white light or as complicated as multiple fixtures with different colors, effects, and rotating gobos.

Sequence
A Sequence (chase) is a series of programmed Scenes (Steps) that may run continuously in a loop when played back.

Scoop
A simple elliptical shaped floodlight usually fitted with a large GLS lamp giving a soft light output.

Screw base
A lamp base spiral-grooved to fit a matching spiral-grooved socket.

Scrim
A mesh material of metal that reduces the level of light.

Secondary colors
Those colors produced by mixing either additive primary colors or subtractive primary colors.

Secondary feeder
A length of cable that clamps to a distribution box and terminates with a number of fused receptacles.

S.C.R. (Silicon Controlled Rectifier)
A solid state current switching device, used in dimmers for lighting systems. It comes from the thyristor family.

Scrim
A fine mesh used in front of a luminaire to attenuate the light beam. They are made with various meshes to give different attenuation characteristics. (See Half scrim.)

SED graph
A spectral energy distribution diagram that illustrates how light is divided into its many wavelengths.

Senior
A 5000-watt fixture, either with fresnel lens or open face seven-fifty A 750-watt fixture, either with fresnel lens or open face.

Show Control
A protocol (language) that allows a variety of different types of devices to be controlled from a central source, such as a lighting console. Typically, a show control protocol will allow you to set up cue lists on a lighting console that play back pages or presets on any controller connected to it.
Show control protocols differ from the DMX 512 protocol in that DMX 512 is typically used to control devices such as lighting fixtures.

SMPTE
Society of Motion Picture and Television Engineers (SMPTE) began work to develop a standardized synchronization method for the new medium. The resulting 'SMPTE time code' is simply the recording of time information, in hours, minutes, seconds and frames, as a digitally encoded signal on one of the tracks of a multi-track audio or video tape. There are a number of frame rates in use today:
24 used in motion-picture film
25 EBU standard (European Television)
29.97 NTSC color videotape standard
30 NTSC monochrome standard (audio) (used by Status Cue)
SMPTE Time code can be recorded to an audio track (Longitude Time Code, or LTC) or it can be recorded as part of the video signal (Vertical Interleave Time Code, or VITC). Either way, the time code 'word' is the same.

"Shower curtain"
A vinyl material hung in front of a fixture to diffuse the light.

Shutter
Metal flags of various shapes used within a luminaire to block light. They are used to shape the light beam from effects spotlights and follow spots. (alt) A moveable cover or screen that can shut out either all the light of a fixture or a portion of it.

Side light
Any light that illuminates a subject at 90 degrees from the axis of the camera, either left or right.

Signal-to-noise ratio
The fixed or approximate relation of the image transmitted through a piece of video equipment to an unwanted interference generated within the equipment itself.

Silk
Any material that has a bright translucence to it and is used as a diffuser.

Single-pole switch
An electrical switch having only one blade and one contact for opening or closing one side of a circuit.

Single purchase
A suspension system for counterweight bars where no gearing is used. The distance of travel of the counterweight bucket will be the same as the barrel. (See Double purchase.)

Six-fifty
A 650-watt open-face fixture.

Skycloth
A scenery unit used to convey the impression of a open sky. (See Cyclorama.)

Skypan
A very shallow scoop used in the film industry, rather like a metal dustbin lid with a bare lamp in the middle.

Snoot
A conical metal tube fitted to the front of the luminaire to enable a reduction in beam size. (alt) A bracket with a solid face except for an opening (sizes vary) that has a long tube that forms a circle of light when placed on the front of a fixture.

Softlight
A luminaire designed to produce virtually shadowless light; generally used to control contrast.

Soft Patching
Configuring multiple single DMX channels to be controlled as a single fixture.

Song
A Song is a collection of 32 Instant Presets and 16 Fader Presets. You can create an unlimited number of Songs within a Show file.

Slip rings
Continuous circles of metal from which the brushes on a motor take or deliver current.

Socket
A device that receives and grips the base of a lamp.

Softlite
Any fixture that utilizes the principle of indirect illumination.

Solid
A large opaque flag used on a butterfly frame.

Spectral energy distribution
The relationship of wavelengths to each other.

Spectroradiometer
An instrument capable of separating and measuring light waves.

Specular
Mirror-like surface that reflects hard rays.

Spherical
A mirror that directs a beam in all directions.

Spigot
The male member attached to a yoke used for the suspension of the luminaire and also for insertion into a floor stand. (Colloq. 'spud'.)

Spike
A singular wavelength that stands alone or predominates a continuous-spectrum curve.

Spill light
Extraneous uncontrolled light from a luminaire.

Splicer
A single piece of cable that has one plug at one end and two (called a Y) or three (called a W) receptacles at the other end.

Spot
To focus a luminaire by moving the lamp/reflector away from the lens, giving a narrow beam. (alt) The smallest, most intense beam obtainable in a focusable fixture; also any lamp that produces a very narrow, intense beam

Spotlight
A luminaire with a focusing system to concentrate the light beam and thus give greater operational control.

Spud
A short metal projection at the center of a fixture's yoke that fits into a recess on a light stand, or into a pipe clamp.

SRAM
Static Random Access Memory. The type of memory used for backup and restore functions using a RAM card.

Stage left/right
The performers' left and right as they face the audience.

Stand
A telescopic floor-mounted tripod device which provides a means of adjusting the height of luminaires above floor level. Can be manual lift, or by a geared wind-up system.

Step lens
A plano-convex lens similar to a Fresnel lens but with the concentric rings cut into the plano side.

Studio area
The total floor area contained within the walls of a studio which may not always be used as the acting area, due to fire lanes, etc.

Studio arc
A fixture with carbon electrodes that does not contain a mirror or aperture; it relies only on the electrode flame for intensity.

Subtractive color mixing
The removal of light of various wavelengths, by filtering or reflection, e.g. a magenta filter subtracts the green from the light path, whereas the pigment of yellow paint reflects the red and green components of the incident light but absorbs (subtracts) the blue. (See Additive Color Mixing.)
(alt) The creation of colors by filtering out (subtracting) certain wavelengths from a typically white (multi-wavelength) light source. For example, putting a magenta filter in the path of a white light source subtracts green light. Typically, the filters used in a subtractive color mixing system are cyan, yellow and magenta; thus, this is usually referred to as the CYM color mixing model. This is the color mixing model used in Cyberlight.

Switch
A device for making or breaking a contact in an electrical circuit.

SYSEX
System exclusive protocol. A subset of MIDI. Allows MIDI to inact with a particular device that is configured for a particular Sysex whilst ignoring other devices on the same MIDI chain because they do not have the same sysex.

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Target
A circular flag 3 inches (76.2 millimeters) or larger that may be of opaque, net, or diffuse material and used to intercept light rays.

Target area
Also called image plate; the area in a video camera where light rays are focused and registered.

Teenie
A 650-watt open-face fixture.

Telescope
A grid-mounted device made from retractable sets of tubes used to suspend luminaires at varying heights in the studio. Older types of telescopes were driven by portable power tools; modern systems are generally equipped with integral electric motors.

Ten-K
A 10,000-watt fixture with fresnel lens.

Terminator
A terminator is a resistor inside an XLR connector. It is used to prevent the analog signal from continuously "echoing" up and down a given data link.

Throw
Generally describes the direction of light from a luminaire and also the effective distance between the luminaire and the area being lit.

Titan
A 350-amp carbon arc.

Tilt
Term describing the vertical movement, about a point, of luminaires or equipment.

Tip/Ring connector
The type of connector typically used for monaural audio sources.

Tip/Ring/Sleeve connector
The type of connector typically used for stereo audio sources.

Trackball
A polymer ball, (about the size of a typical billiard ball) that is mounted in a frame which is provided with directional sensors. The Trackball is moved in various directions in order to interface flexibly with a computing device.

Transformer
A device that increases or decreases the flow of current

Transverse wave
A wave in which the electric field moves perpendicular to the line of light travel.

Trackspot
An automated compact moving mirror luminaire manufactured by Lightwave Research. Trackspot has 10 colors,10 Gobos, Dim, and Strobe.

Tower
A temporary platform, usually made from scaffolding, on which to mount luminaires.

Truss
A framework, generally made from alloy bars together with cross-bracing, to provide lightweight rigging structures.

Tungsten halogen
Describes a family of lamps with either hard glass or quartz envelopes, tungsten filaments and halogen (usually iodine or bromine) fillings. (alt) An incandescent lamp containing a regenerative element.

Tungsten-to-daylight
A term referring to the conversion by filtering of tungsten light to a color temperature compatible to daylight.

Twistlock
A connector that is engaged by a turning motion so it cannot be pulled loose and is disengaged by an opposite motion.

Two-K
A 2000-watt fixture with a fresnel lens, or open-face.

Ultraviolet (UV)
The band of short-wave radiation from 400 nm to 10 nm; although invisible to the eye the energy is extremely powerful and produces reddening of the skin (sunburn); it can also cause damage to the eye.

Underwriters laboratory (UL)
An American independent test laboratory that ensures minimum safety standards of equipment.

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Video
A reference to visual electronics.

Voltage
Electromotive force.

Voltage drop
That loss of volts that occurs through energy wastage when a current passes through a cable or electronic device.

Wash
General ambient light on the acting area.

Watts
A measure of electrical power (Volts x Amps = Watts).

Winch
Term used to describe either manual or motorized lifting equipment.

Wire rope
Ropes formed from fine wires woven in complex patterns to give great strength.

Working lights
(See House lights.)

XLR Cable/Connectors
Cables and connectors typically used to interface (or daisy chain) automated lighting fixtures and controllers.
Most Lightwave Research XLR connectors have three pins:
Pin 1 = shield
Pin 2 = negative
Pin 3 = positive

Yoke
The suspension frame of a luminaire; possibly containing the drive mechanism for pan and tilt. (Colloq. fork, stirrup, trunnion.)

Zoom
A motorized mechanism which allows you to effectively alter the beam size while maintaining focus.
(alt) Used in profile spots and scenic projectors, consisting of the relative movement of two lenses in an optical system to change beam width and focus.