Glossary

AMBIENT LIGHT - The existing light before any supplementary light is added.

AMP - (Ampere, A) The unit of electrical current. Small (1 kW) lights use nearly 5 amps. Larger (3 kW) lights use 15 amps.

APERTURE - The variable-sized opening in a lens that controls the amount of light passing through the lens. Large apertures have small f-numbers, small apertures have large f-numbers.

ARTIFICIAL LIGHT - Light that is produced by any source other than sunlight.

AVAILABLE LIGHT - Existing light that is deemed suitable to produce reasonable quality pictures.

BACK LIGHT - Light from behind a subject creating a bright rim to help separation from a background.

BARN DOOR - Two- or four-bladed, hinged shutters fitted to a luminaire to shape the beam.

BLACK LEVEL - The electronic reference level in a video picture signal which represents pure black. Many cameras allow this to be adjusted to suppress shading.

BLACK OUT - To simultaneously turn off all the lights. Most lighting consoles have a DBO (dead black out) switch to make this easy.

BOUNCED LIGHT - Light reflected from a special reflector, a suitable wall or ceiling to produce a soft diffuse effect.

BRIGHTNESS - The perceived amount of light emitted by a source.

C-CLAMP - Standard fixing allowing a luminaire to be mounted on the lighting grid.

CCT - (correlated colour temperature). The closest colour temperature value of a light source derived from a discharge lamp.

CHANNEL - One continuous circuit from the fader on a lighting console through to a particular luminaire.

CHASE MODE - A type of lighting special effect where luminaires are switched on (or off) in a pre-determined sequence.

CHROMINANCE - The part of the electrical video signal carrying colour information.

COLOUR BALANCE - The process of modifying light from different sources so they all equal the same colour temperature.

COLOUR CORRECTING FILTER - (CC filter). A special filter that is used to adjust the colour temperature of a source to the required value.

COLOUR FILTER - (Gel). A coloured piece of material deliberately placed in front of a luminaire to alter the colour of the beam.

COLOUR TEMPERATURE - The relative temperature of a light source expressed as degrees on the Kelvin Scale. Daylight is taken as 5600°K, tungsten as 3200°K. 0°K is -273°C.

CONDENSER LENS - A lens which collects light from a lamp and condenses it to a narrower angle. Used in profile spotlights. The term is sometimes used for fresnel lenses which condense the output from the lamp in the spot position.

CONSOLE - Equipment used to control the brightness level of individual or groups of luminaires through dimmers. Similar to an audio mixing desk.

CONTRAST - The visual range within a scene between the lightest and darkest.

CONTRAST RATIO - The ratio between the brightest and darkest parts of a scene as measured by a light meter. Video cameras can handle ratios of about 1:64.

COOKIE - (Cukaloris). Specially made shapes that are placed in front of a luminaire to cast a shadow onto a background. An example would be shadows of branches made from a piece of ‘branch shaped’ wood.

CROSS FADE - The lighting equivalent of a mix. One luminaire (or set of luminaires) is faded out whilst another is faded in.

CSI LIGHT - (compact source iodide). A discharge light source with a CCT of approx 4000°K.

CUE - A signal which causes something to happen, as in lighting cue (the point at which the lighting changes).

CUKALORIS - See Cookie.

CYC LIGHT - Special type of luminaire that is designed to illuminate the background curtain.

DAYLIGHT - Light produced by the sun. Nominal daylight is 5600°K, but a cloudy sky may reach 6500°K, bright blue sky may reach 10,000°K.

DEPTH OF FIELD - The distance between the closest and the furthest objects that are in focus. Note: this can be changed by altering the aperture setting.

DICHROIC FILTER - Special glass filter which will transmit selected colours whilst rejecting others. Used as colour correction filters, beam splitters in cameras or to separate infra red (heat) and light reflected from special mirrors integral with a bulb.

DIFFUSER - A scrim or a gel fitted to the front of a luminaire that has the effect of softening and spreading a light beam.

DIMMER - Electronic unit allowing continuous, smooth variation of the power output of a luminaire.

DOWSER - A small metal blade inside a follow spot that enables the beam to be cut off without switching off the power.

DROP ARM - Lighting suspension used to extend a luminaire downwards from the lighting grid.

EXPOSURE - Literally, allowing light to fall onto a photosensitive surface for a controlled amount of time.

F-NUMBER - A set of numbers that indicate the size of the aperture within a lens. Small numbers represent large apertures and big numbers small.

FADE - A smooth change of brightness from a luminaire or a group of luminaires.

FADER - The device that controls fades. Often a slider but, increasingly these days, it could be a wheel.

FALL OFF - The gradual loss of intensity across the width of a light beam.

FILL LIGHT - A luminaire (usually giving soft light) used to control the contrast of a scene by providing extra illumination in dark shadow areas.

FLAG - A piece of shaped opaque material placed so as to interrupt a light beam and either hide the light from the cameras view or prevent a shadow falling onto a particular area.

FLOOD LIGHT - A luminaire giving a broad wash of even (usually soft) light. Often used as a fill.

FOCUS - To adjust the optics of a luminaire to provide a sharp beam.

FOLLOW SPOT - A luminaire mounted onto a stand and manually controlled so that the beam follows a performer as he or she moves around the set.

FRESNEL LENS - A special lens that is made by taking cross sections of a piano convex lens and welding them together to form a thinner, lighter lens.

GAFFER - The senior lighting engineer. GEL – See Colour filter.

GOBO - Shaped cut out fitted into the gate of a profile spot to project a hard edged shape onto a background.

GRID - See Lighting grid.

GROUP - A control on the lighting console that will simultaneously affect several chosen channels.

HEAT FILTER - A filter (often dichroic) which removes the infra red (heat) rays whilst allowing the light to pass through.

HIGH KEY - Description of a scene which has large areas of brightness with very few shadow elements.

HIGHLIGHT - The brightest part of a scene.

HMI LAMP - (hydrargyrum mercury iodide). A discharge light source available with a CCT of 5600°K (daylight).

HOT SPOT - A small area within a light beam that is excessively brighter than the overall light level.

KELVIN - Temperature scale used to express the thermodynamic value of a light source. 0°K = –273°C.

KEY LIGHT - A luminaire providing hard light positioned so that the shadows it casts on the subject give an impression of shape and texture.

LAMP - The glass container within a luminaire or lantern which produces light. Also known as a ‘bubble’ or bulb. Also refers to a luminaire in some sections of the industry.

LANTERN - Another word for luminaire.

LENS - The optical system in a luminaire that allows the light beam to be focused.

LIGHT - The output of the lamp, which is emitted from the luminaire, and controlled by the lighting team.

LIGHTING GRID - The barrel structure, fitted above the acting area, from which the luminaires are suspended.

LIGHTING PLOT - A plan, drawn to scale, indicating which luminaires are to be placed where on the grid and at what level, for a particular scene.

LIGHTING RIG - A plan showing the normal position of the available luminaires fitted to the lighting grid.

LOW KEY - Description of a scene which has large areas of mid to dark light.

LUMEN - The unit of luminous flux. Measure of how bright a light is.

LUMINAIRE - A unit designed to give out a controlled beam of light. The basic tool of the lighting team.

LUMINANCE - The part of the electrical video signal carrying brightness information.

LUX - The unit of illumination. 1 lux = 1 lumen per square metre.

METAL HALIDE LIGHT - The group name for discharge sources such as HMI and CSI lights. They take two to three minutes to reach full brightness, and cannot be used with normal dimming circuits. Some provide a small degree of dimming control or venetian blind type shutters can be used.

MIXED LIGHT - Light coming from a number of sources with different colour temperature values, e.g. tungsten light in a room with daylight.

MODELLING LIGHT - Light cast from a particular angle to create shadows to show shape. See Key light.

NEUTRAL DENSITY FILTER - A filter that will reduce the light passing through it by a known amount without affecting the colour (often shortened to ND).

OHM - The unit of electrical resistance. The electrical symbol is Ω (omega).

OVERLOAD - A dangerous situation where too many lights are connected to the same circuit, causing, at best, the fuse to blow or, at worst, damage to the lighting console or dimmers.

PANTOGRAPH - A Lighting support consisting of a lattice network that can be extended four or five metres below the lighting grid.

PARABOLIC REFLECTOR - A special shaped mirror that will focus a light beam.

PAR LIGHT - The name given to a sealed-beam unit producing an oval-shaped beam. Because the lens is welded to the front of the bulb, both flood and spot varieties are available.

PATCH PANEL - A system of connectors allowing different luminaires to be supplied by alternative dimmers.

QUARTZ IODINE LAMP - (QI). A tungsten filament light which is enclosed in a quartz envelope. The iodine inside the bulb prevents blackening.

REFLECTOR - Any shape or form of material that is used to bounce light, directed at it, back from it in a predetermined direction.

SCOOP - A large luminaire specially constructed to give soft light.

SCRIM - A metal mesh fitted in front of a luminaire to reduce the light intensity. Also textile panels to diffuse light.

SCR - (silicon controlled rectifier). An electronic device used in dimming circuits.

SHUTTERS - Small metal blades fitted in the gate of profile spotlights luminaires to shape the light beam. Also a venetian blind arrangement for dimming discharge luminaires.

SNOOT - A tube placed in front of a luminaire to modify the shape of the light beam by making it smaller.

SOFT LIGHT - Light that casts diffuse or edgeless shadows. Usually comes from a large source.

SPARKS - The electricians in the lighting team.

SPILL RINGS - Concentric cylinders placed in front of a light source to control the spread of the light beam.

THYRISTOR - Electronic switching device used in SCR dimming circuits. TUNGSTEN HALOGEN LIGHT – Artificial lights which have a tungsten filament. The filament may be fitted inside a normal envelope or a quartz envelope.

UV LIGHT - Ultraviolet light. Light that is emitted by the sun and some artificial light sources but which cannot be seen. Causes burning to the skin and can damage the eyes.

VOLT (v) - Unit of electrical pressure. Europe uses 220 volt, Parts of the USA use 110 volt. Bulbs run on the wrong voltage will either explode or be excessively dark and red in colour.

WATT (w) - Unit of electrical power. The more watts, the more powerful a luminaires light output.

XENON LAMP - Discharge light which is unusual in that it produces a near continuous light spectrum. Has a colour temperature close to daylight.