4. Lighting Guide

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Lighting Guide - Basic Lighting

The first question we have to ask is what we need lighting to do. This is a fairly basic process but

one which must be remembered when one is using lights and building a lighting plan.

Lights are used to:

Enable the audience to see the performers

Enable the audience to see the set

Create a mood

Inform the audience of part of the story and scene

Light the audience

Light Sources

In the beginning, there were candles, and not much else. They were a fire hazard and what little

light they did produce was extremely yellow. Eventually, people began to burn quicklime, producingmore light (although this was fairly green in colour).

Gaslights were more reliable, easier to control but even they were not very flexible and still meantburning stuff in a theatre full of people; not particularly safe.

In 1879, Thomas Edison and Joseph Swan demonstrated the first effective filament lamps to theworld. The process was simple: pass an electrical current through a very thin metal wire, encase it

in an oxygenless environment to prevent it from oxidising and wait for the wire to heat up to atemperature at which it emits light. Most theatre lamps still use this process although other methods

of light emission are used for more expensive lights.

Colour emission

Assuming we use a filament lamp, we need to know a little about the way it produces light. Theelectricity passing through it is solely to heat the metal filament up; it is the temperature of the

metal which is all-important.

As the metal's temperature increases, it starts to emit infra-red, then red, orange, yellow, blue andfinally white. A hot filament will produce a small amount of orange light, giving the light beam from

the light a dull orangey red appearance. A very hot filament will produce lots of red, orange as wellas all the other colours in the visible spectrum, giving the appearance of a bright white beam.

Ordinary house lights (~60W) run at relatively low temperatures, giving a fairly dark, yellowy light.Theatre lights (~500W-1kW) run at higher temperatures, giving bright, slightly yellow beam whilst

lights such as Par64s (1kW) run at even higher temperatures and produce a very bright, whitebeam. The important things to remember are that different lights produce light of different colours

and intensities and as you dim any light, it will start to produce a more orangey beam.

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Bits of a light

Filament: bit of thin metal which is heated up by an electrical current, producing light in all

directions Reflector: a reflective surface which directs light in a particular direction. The reflector can

be any shape but the most common cross-sections are circular or oval to form the light rays

emitted from the filament into a beam of light.

Lens: a shaped piece of glass to redirect the light rays as they pass through. Although mostlights use a normal curved (plano-convex) lens to produce an accurate image, these lenses

tend to be thick and so heavy. The other option is the Fresnel lens which uses a series ofconcentric rings of glass to focus the light, enabling a light but powerful lens to be produce.

Shutters: a series of metal plates that can be used in some lights to shape the light beam

emitted. With the shutters fully retracted, the beam is circular but with them pushed in, thelight beam can be square or rectangular.

Barndoors: a set of flaps that can be used on some lights to restrict the light emitted. They

act like shutters but are not as precise and are generally used to stop spilled light. Gobo: A gobo is a piece of metal (or in some cases, glass) which can be placed inside some

lights to block out parts of the light. This sillouette is projected as a shape of light and so

allows patterns of light to be formed. Many hundreds of gobos are available in standardpatterns, logos, text and shapes and they can also be custom produced if required.

Gel (or colour filter): White light may show what is happening on stage but it doesn't really

create a mood and gets a bit boring after a while. Gel is a coloured sheet of plastic which isfixed to the front of a light inside a gel frame and which produces a coloured light beam. Like

gobos, there is a vast number of standard gel types made by a number of companies. Here'sa rough guide to their effects:

Red: angry, dramatic

Blue: cold, night time

Pale purple: neutral

Orange/yellow: warm

Dark colours are usually used for lighting bands and since they absorb lots of light, they can

get very warm and eventually melt.

Paler colours are more suited to theatre lighting where subtle mood setting is required.

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Types of light

Fresnel

A light which uses a circular reflector and which is named after the lenswhich it uses. The Fresnel lens is not very precise however and gives a very

soft edged beam as well as spreading a great deal of light outside the beam

(spill). The light can be focused in order to alter the size of the light beambut it cannot project gobo images. Despite being not particularly efficient,the Fresnel is a good light for stage lighting, especially at close & medium

ranges to the subject.

Profile

An efficient light which uses one or more lenses and an ellipsoidal reflectorto focus the light into a sharp beam. They usually have a longer body than

Fresnel and can be focused to form a sharp circular beam with little spill.This sharp beam enables the light to project gobos as well as using shutters

to project a specifically shaped light beam. Most profiles have a fixed beam

angle although zoom profiles are available, giving an adjustable beam size.Profiles are suited to projections and for lighting at medium and long rangesfrom the subject.

PC (Pebble Convex)(Plano-Convex)

A cross between a Fresnel and a Profile which uses a rough reflector to

diffuse the light, producing a beam which is similar to an out of focus

Profile. The PC is more efficient than a Fresnel and also produces less spill.

Flood

An uncontrolled light which produces a very large area of illumination. It hasno lens and relies on a large reflector to direct the light out, resulting in a

cheap and efficient light which produces enormous amounts of spill. Anasymmetric floodlight directs more light upwards and is used to light flat

walls (or cycs). This means the part of the surface furthest away gets morelight and so the wall is evenly lit. Floodlights are generally used to produce

large colour washes.

Parcan

This light is built around it sealed lamp, consisting of lens, filament andreflector. This arrangement produces an extremely robust bulb able to

operate at high temperatures and for short flashes. The Parcan has a metaltube around the front of the bulb, giving a very cheap, powerful light which

weighs little but produces a very bright, white light. The beam can't befocussed and is a soft ellipse with little definition. The Parcan is suited to a

wide range of duties, most notably band lighting.

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Use of light

From above: gives a very dramatic effect with very dark shadowsshowing little of the face.

From the front: gives good illumination of the face but produces a very

unnatural 2D effect.

From the back: gives a silhouette effect, showing little detail of theperson's face but giving a good indication of their posture and

movement.

From the back, front and both sides: gives a good overall effect withdetail, natural shadows and an appearance of 3D. The lights should be at

the correct levels (possible also using gel) to get the best results.

Control and connections

A light requires power and although it could be controlled with a simple light-switch, we usually want

to be able to alter the intensity of the light. To do this, we need to use a dimmer which varies theamount of power sent to the light. The dimmers in theatres are built into rooms where they can

operate safely, reliably and quietly. The dimmers are controlled remotely by a lighting desk.Working backwards in the chain:

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Light: receives power and emits light

15 amp cable: most lights are powered through a 15A cable. This is exactly the same as

your normal 13A mains wiring except that the cable can carry more power and the socketsare a different round-pin design to ensure that only 15A plugs can fit 15A sockets.

Multicore cable (named Lectroflex): The dimmers may be 50m from the dimmers and it

should be obvious that its a bad idea to power 100+ lights by using an individual 50m cablefor each light. To reduce the cost of this (and the effort of installing hundreds of long cables)

multicore wiring is used. This carries 6 of the normal 15A cables in one cable and allowseasier connection. At the light end, an adaptor is used to split the multicore cable up into 6

separate sockets.

Dimmer: the dimmer sends a variable amount of power out to the light via the powercabling. Last century, the dimmers were controlled manually but today they are controlled

remotely by lighting desks.

Control cable (named DMX512 cable): When lighting desks were first used, each channelon the desk would send a voltage by a wire to its dimmer. A signal of 10V would direct the

dimmer to turn the light fully on, a signal of 5V would indicate the light was to be at 50%output. This meant that for many lights, many channels would be used and so hundreds of

control cable would be used.This was difficult to set up, expensive, unreliable and prone to interference so in the last ten

years, a digital form of control began to be used. A single cable would be used to send the

information of what level the channels were at and this could cope with controlling 512channels. For more information, see our section on DMX.

Lighting Desk: Simple desks consist of a series of faders that control a channel each and byusing two sets of faders, the lighting controller can change from one state to another by

using a crossfade control. Although this is simple, it is very time consuming and so moderndesks use computer control to set up the lighting with each scene being saved into memory

and then outputted as the lighting controller requires.

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4. Lighting Guide