Glossary of Terms - L

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.

L

LADDER
Non-climbable structure in the shape of a ladder from which lanterns can be hung in a vertical "stack".

LAMP
A light bulb is used in domestic situations (i.e. in the home). In the industry, we only use LAMPS. As the saying goes, "Bulbs is what you put in the ground". Example usage: "The lamp in the DSC fresnel has blown". In the TV/Film world, a lamp is called a BUBBLE.

LAMP LIFE EXPECTANCY
The time that the lamp can keep its projected screen lumens higher than 50% of the initial value.

LAMP TRAY
Lower section of the body of a theatre lantern on which the lamp holder is mounted. Some lamp trays are hinged, some are removable from the rest of the body. Modern safety legislation (UK) requires that the lamp tray cannot be opened until power is disconnected.

LAMPY
Theatre / Rock & Roll lighting technician. Distinct from a "Techie" who may also be a carpenter or stage crew member. A lampy only concerns him/herself with lighting.

LAN
Local Area Network. A high volume data transmission signal is returned to the sending device after passing through all or part of a communications link or network.

LANTERN
General term for unit of lighting equipment including spotlight, flood etc. Term now being replaced by the internationally recognised "luminaire" (esp. Europe) or "instrument" in the US.

LASER
Acronym of Light Amplification by Stimulated Emission of Radiation. A very high energy beam of light that remains
virtually parallel throughout its length. Visible in the air only when a haze of smoke or dust is introduced. Great care is required when using lasers as this energy can cause permanent damage to the retina of the eye.

LASER POINTER
A small pen or cigar sized pointer that contains a small battery powered laser. The laser pointer projects a small, red (typically), high intensity beam of light.

LCD
LCD stands for liquid crystal display and comes in many forms, sizes, and resolutions. Its primary purpose is to present a digital image for viewing. A common use of LCDs is as a display on a notebook computer.

LCOS
Liquid Crystal On Silicon. This consists of mirror electrodes on a silicon substrate and transference electrodes on a glass substrate, enclosing vertically aligned liquid crystal. LCOS requires a far smaller light blocking layer that allows it to achieve a much higher aperture ratio (92% as opposed to 40-60% for conventional)

LD / L.D.
Lighting Designer.

LECTRIFLEX

    Multipin connector for carrying multiple lighting circuits down a multicore cable.
    Also see SOCAPEX.

LED / L.E.D.
Light Emitting Diode, a semiconductor device that produces visible light when a voltage of a certain polarity and potential is applied to it. LED technology is becoming extremely useful in the areas of architectural lighting and video walls. LED light sources are becoming brighter and cheaper. They are extremely efficient, and give off very little heat, making them ideal for display or architectural work. LED video walls are in use all over the world - they are more efficient and lighter in weight than projection alternatives.

LEKO
A type of ellipsoidal profile spot, much used in the USA. Contraction of the original manufacturers names.

LENS
Optical glass with one or both sides curved, the purpose of which is to direct light by concentrating or dispersing light beams.

LIGHTING BOARD
See BOARD.

LIGHT CURTAIN
A lighting effect which, when an area is diffused with smoke, produces a wall of light. Produced (usually) by a batten of low voltage PAR lamps wired in series. Automated versions are available which have colour changers built-in and are able to tilt up and down. (See DIGITAL LIGHT CURTAIN)

LIGHTING PLAN
A scale drawing detailing the exact location of each lantern used in a production and any other pertinent information (E.g. its dimmer number, focus position and colour number). Often drawn from the theatres' groundplan.

LIGHTING PLOT
The process of recording information about each lighting state either onto paper or into the memory of a computerised lighting board for subsequent playback. (in USA, this term is used for a lighting plan and a lights session is when lighting states are set up.)

LIGHTING STATE
The format of lighting used at a particular point in the production; a lighting "picture".

LIGHTING STENCIL
Plastic stencil containing a range of scale symbols for current lighting equipment. Greatly facilitates the drawing of lighting plans.

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

LIMITER
An electronic circuit used to prevent the amplitude of an electronic waveform from exceeding a specified preset level while maintaining the shape of the waveform at amplitudes less than the preset level.

LINEAR
Having an output that varies in direct proportion to the input.

LINEAR FREQUENCY SCALE
A scale on which each equal length division represents an equal number of Hertz. If you add the equal length division in Hertz to the last division frequency, you get the next frequency in a series.

LINE OUT
An output connection found on mixers, preamps, tape decks, etc. providing an output at a level sufficient to drive the input of a power amplifier.

LINK
See POINT CUE.

LOAD

    The electrical power rating, in Watts, of the equipment connected to a particular lighting dimmer.
    The equipment connected to a dimmer.

LOAD IMPEDANCE
The actual impedance of the load or speaker that a power amplifier is connected to, thus driving a load of a certain impedance.

LOBSTERSCOPE
A mechanical device that reproduces the flashing "motion-freezing" effect of a strobe.

LOGARITHMIC FREQUENCY SCALE
A scale on which each division represent an exponential constant, i.e., each division from a reference point is proportional to its logarithms.

LONG THROW LENS
A lens designed for projection from the back of a room, or rather the back of a large room. Long throw lenses would be used in a projection booth in the back of a theater, etc. A typical long throw lens might have to be 15 to 30 from the screen to project a 120" diagonal image.

LOUDNESS CONTROL
A volume control with special circuitry added to compensate for the normal decreased hearing ability of the human ear at the extreme ends of the audio range when listening to lower sound levels. A typical loudness control boosts the bass frequencies and to a lesser extent, the high frequencies. Sometimes this control is called contour.

LOUDSPEAKER EFFICIENCY
The ratio, expressed in percentage, of signal output to signal input used to state the power needed to drive a loudspeaker. An example: Power output 2 watts; Power input 10 watts; Ratio 2/10=20% efficiency. Efficiency can vary from 2% to as high as 25%.

LOW PASS
All of the frequencies below a given crossover frequency.

LOW SMOKE

    Smoke that has been chilled as soon as it comes out of the smoke machine. This causes the smoke to lay close to the floor. Use fast dispersing smoke for this effect because when the smoke heats up in the air, it will rise.
    Also see DRY ICE.

LOW VOLTAGE
Lower voltage lamps give more intense light than mains voltage lamps of the same wattage.

LOW Z OR LOW IMPEDANCE
Any resistance to AC voltage or current flow generally less than 2000 Ohms.

LTP
Latest Takes Precedence.

LUMEN / LUMENS
A standard for measuring light output used for comparing light output. The brightness of projectors is stated in Lumens. However, the rating does not always match the perceived brightness. For example, if one projector uses halogen lamps and another metal-halide, the halogen projector will seem noticeably dimmer, even if the two units rate the same.

LUMINAIRE
The international term for lighting equipment. Not restricted to theatre lighting.

LUX

    A measure of the level of illumination on a surface (1 lumen spread over 1 metre).
    A standard for measuring light, numbers provided by manufacturers usually do not provide necessary additional information to compare one product to another.

LX
Short for Electrics. The department in the theatre responsible for stage lighting and sometimes sound and maintenance of the building's electrical equipment.

LX TAPE
See PVC TAPE.

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