Glossary of Terms - F

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.

F

F.B.O.
Abbreviation for Fade to Blackout.

FADE
A fade is an increase, diminishment or change in lighting or sound level.

FADE TIMES
On computerised memory lighting control desks, a lighting fade can have two times - an up fade and a down fade. The Up fade time refers to the time it takes dimmer levels to rise to their new positions. The Down fade time refers to the time for dimmer levels falling to their new positions.

FADER
A vertical slider which is used to remotely set the level of a lighting or sound channel.

FAR FIELD
That portion of the direct field that is at least twice the distance of a frequency's wavelength.

FEED

    A power supply to a piece of equipment or installation is termed a "feed". Sound equipment and sensitive computer equipment should have a clean feed - that is, a supply that is free from interference from other equipment.
    A signal from one system to another is also known as a feed (for example, an audio signal from the FOH desk to a TV company videoing a concert is known as a feed.)

FEEDBACK
(Electronic) The return of a portion of the output of a circuit to its input. (Acoustic) A squeal of a sound system caused by the regeneration of a signal from the output of a sound system into a microphone input.

FERGO
A custom made plastic gobo that is suitable in certain lights.

FESTOON

    Describes tabs which adopt a sculpted shape.
    A length of cable incorporating a number of lamp holders used for outdoor party lighting etc. Available in multi-circuit form so that the lamps can be "chased".

FIBRE FRAME
A gel frame made from heat resistant fibres, which doesn't get as hot to the touch as a standard metal frame.

FIBRE OPTICS
A method of directing light down a very thin glass fibre. Fibre Optics are used mostly in communication, but find theatre applications in star cloths which are black backcloths with the ends of optical fibres poked through, to create a mass of pin pricks of light. A large bundle or harness of fibres may be fed from one light source, sometimes with a motorised colour or flicker wheel. New technology enables digital sound signals to be sent down optical fibres now, replacing heavy and expensive multicore cables.

FIELD
Refers to the spread of light intensity across a beam. Most profile lanterns have an adjustable field. A Flat field has an even distribution, a peak field has a "hot spot" in the centre of the beam. A flat field is essential when using gobos. See PROFILE.

FILL LIGHT
(especially TV and Film lighting) Light which fills the shadows that key light creates.

FILTER
An electrical or electronic device that permits certain frequencies to pass while obstructing others. Examples include loudspeaker crossovers, equalizers, feedback reducers and even simple bass and treble controls.

FIRE EXTINGUISHER
Essential tools of the pyrotechnician's trade ! In the UK, they used to be colour-coded according to content (Carbon Dioxide (Black), Water (Red), Foam (Cream), Halon Gas (Green) Powder (Blue)) but now, they're all red with a small label saying what they are. Another great leap forward !.

FIRST ELECTRIC
The first LX bar upstage of the proscenium arch. (Also known as LX1).

FIT-UP
Initial assembly on stage of a production's hardware, including hanging scenery, building trucks etc.

FIXTURE
Used to describe a type of moving light.

FLAGGING
When focussing lighting, flagging means waving your hand in and out of the beam of a lantern/instrument in order to see where the beam is hitting on stage. Flagging is particularly useful in high ambient light levels. (e.g. "Can you flag that please ?") Term probably originates from a FRENCH FLAG.

FLASH BOX
A small box containing the socket into which a pyro cartridge is plugged. Also known as a flash pod.

FLASH BUTTON
A push switch on a lighting desk which flashes selected channels / memories / submasters to full (100%) while pressed. Some Flash buttons on submasters can be set to latch (ie they stay on when pushed, until they are pushed again).

FLASH OUT / THROUGH
Method of checking whether lanterns are functioning properly by flashing them on one at a time. It is good practice to flash lanterns to 70%, rather than Full to preserve lamp life.

FLIGHTCASE / FLIGHT CASE
Metal framed wooden box on wheels with a removable lid used for transporting equipment between venues. Flightcases are very strong, and have reinforced corners and edges. Care should be taken when lifting flightcases as they can be very heavy.

FLOOD

    A lensless lantern that produces a broad non-variable spread of light. Floods are used in battens, or singly to light cycloramas or large areas of the stage.
    To increase the beam angle of a focus spot by moving the lamp and reflector towards the lens. "Flood that a bit, please !"
    A flood light is also refered to as a Q.I. Flood.
    See also CYC FLOOD.

FLOORCANS
A PARCAN with an extra trunnion arm / yoke, and often a short nose, which is designed to sit on the floor.

FLOORPOCKET
A electrical socket mounted under a flap in the stage floor.

FLUORESCENCE

    The property of some materials to glow when subjected to light. This normally refers to ultraviolet light, although blue visible light (along with many other colours) can cause fluorescence. The materials degrade the UV wavelengths into longer and therefore visible reflected rays.
    See also PHOSPHORESCENCE.

FLUTTER ECHO
A multiple echo in which the reflections occur in rapid succession caused by large surfaces being acoustically parallel to each other.

FLY BARS
The metal bars to which scenery and lanterns are attached for flying above the stage.

FM BASED REMOTE
A remote control that broadcasts its instructions with an FM transmitter, normally required in large rooms, thanks to long range, and no line of site requirement.

FOCAL LENGTH
The distance between the focal point of a lens or mirror in a projection device and the corresponding principle plane.

FOCUS

    The session when all the lanterns in the rig are angled in the correct direction, with the correct beam size.
    Description of how sharply defined a light beam is ("give that profile a sharp focus")
    Control on projection equipment used to change the focus.
    Sharpness of a pixel or series of pixels on the projection screen faceplate. Also measured as the spot size.

FOCUS SPOT
Term for both Fresnel and PC type lanterns with adjustable beam size.

FOCUSING
The process of adjusting the direction and beam size of luminaires and projectors. Does not necessarily result in a "sharply focused" image.

FOH
See FRONT OF HOUSE.

FOLLOW-ON CUE / FOLLOW CUE
A cue that happens so soon after a previous cue, that it doesn't need to be cued separately. The follow-on can be taken by the operator once a previous cue is complete, or a lighting or sound cue can be programmed to happen a specific time after a previous cue. Fly follow-on cues are often taken as soon as the operator has completed a previous cue. Often abbreviated to F/O.

FOLLOWSPOT
Usually, a powerful profile lantern usually fitted with its own dimmer, iris, colour magazine and shutters mounted in or above the auditorium, used with an operator so that the light beam can be moved around the stage to follow an actor. Sometimes a beam light or other lantern may be used in the same way. See PICK-UP.

FOOTLIGHTS
A compartmentalised batten sometimes recessed into the front edge of the stage, used to neutralise shadows cast by overhead lighting. Modern lighting equipment renders footlights virtually obsolete except for period/special effects.

FPS
Frames Per Second.

FRACTIONAL T1
A service provided by carriers, where a full T1 link is leased to a customer, but the service charge is based only on the number of time slots used.

FRAME
A single refresh of the entire screen as perceived by the viewer. This is two fields in an interlaced system.

FRESNEL
(pronounced "Fre-nell") A type of lantern which produces an even, soft-edged beam of light through a Fresnel lens. The lens is a series of stepped concentric circles on the front and pebbled on the back and is named after its French inventor, Augustin Jean Fresnel (1788-1827). He developed the lens for French lighthouses so that they could be seen further out to sea and could achieve a longer focal length with a lot less glass than a standard plano-convex lens.

FREQUENCY
The number of vibrations or oscillations in units per second. Measured in cycles or Hertz per second. The rate of repetition in cycles per second (Hertz) of musical pitch as well as of electrical signals. For example, the number of waves per second a vibrating device such as a piano or violin string moves back and forth each second of time to produce a musical tone.

FREQUENCY RESPONSE
A measure of the effectiveness with which a circuit, device or system transmits the different frequencies applied to it. The way in which an electronic device (mic, amp or speaker) responds to signals having a varying frequency. This is a measurement of how well an amplifier reproduces and amplifies a specified audible range with equal amplitude or intensity, for example, 30 to 16,000 Hz.

FRONT OF HOUSE (FOH)

    Every part of the theatre in front of the proscenium arch. Includes foyer areas open to the general public.
    All lanterns which are on the audience side of the proscenium and are focussed towards the stage.
    The backstage areas of the theatre are known as Rear of House (ROH).

FROST
A diffusing filter used to soften the edges of a light beam. Frosts are commonly used in profiles in front of house positions to achieve the same beam edge quality in all lanterns. Different strengths of diffusion frost are available from many colour filter manufacturers. See also SILK.

FULL DUPLEX
A system capable of transmitting and receiving signals simultaneously.

FULL RANGE
The entire audio spectrum, 20 Hz - 20 kHz.

FULL UP

    A bright lighting state with general cover lanterns at "full" (100%) intensity.
    Also see FULL UP FINISH.

FULL UP FINISH (FUF)
A shorthand note for manual desk lighting operators to bring all relevant dimmers to full for the end of a song / finale of a show to "draw the applause".

FUSE
Protective device for electrical equipment (E.g. dimmers). The fuse link will melt when excess current flows, preventing damage to people or equipment. Every piece of electrical equipment has at least one fuse in its associated circuit.

FUZZ LIGHT
A lamp with a revolving mirror and a coloured plastic dome. Gives a "police light" effect. Usually 12 Volt or 240 Volt operation.

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