There are two important objectives of stage lighting the first is visibility, allowing the audience to see clearly those things they should see, in particular the actor's movements and face; and the second is for mood and effect by adding suitable colour and texture or special effects.
To be able to achieve these objectives specific lights, called lanterns, evolved to have very individual purposes. There are four basic types of lantern that are available in a variety of wattages (power). They are:Floods: the most basic lantern, just a lamp in a box, used as wide angle "floods" of light on scenery and backcloths.
Fresnels: lanterns with a fresnel lens provide a soft light. The fresnel lens has a series of concentric rings in 'steps' on it. The adjustable lens allows for varying beam width via its proximity to the lamp, ie: the nearer the lamp is to the lens the wider the beam and vice versa. Fresnels often have hinged flaps called "barndoors" which can roughly shape & crop the beam of light.
Profiles: the lens of a profile lantern looks like a magnifying glass and will project a sharp focussed beam of light. There will be a 'gate' assembly between the lamp and the lens, with shutters to shape the beam. "Gobos" (metal plates with cut out patterns) can be inserted in the gate to project quite complex images.
Beamlights: lanterns similar to floods except that they have no lens. They give an intense, fixed spread of light.
Often in amateur productions lighting is left to the last minute and as a result is often poor and ineffective, spoiling the work of the actors and set designers. For lighting design to be effective there are some important points to remember:
1. After reading the play the lighting designer should be closely involved in the production process with both the director and the set designer, listening to their ideas and contributing ideas about set design, sight lines, masking, mood and costume.
2. It is the task of the lighting designer to establish what equipment and resources are available, and produce a lighting plan using a stage grid.
3. During rehearsals the lighting designer and director need to revise the play scene by scene to plan precise lighting details, working out presets and cues, a lighting summary with the stage manager, as well as purchasing or hiring extra equipment as needed.
4. During the production week the lights should be rigged and focussed. The lighting designer should be present during technical rehearsals for trouble shooting any problems and final adjustments.
Don't use too many lurid colours as above!
Effective stage lighting is now as much a part of a modern day performance as the actors and instrumental in assisting the actors to bring a polished performance to the audience. The following annotated online bibliography has been included for further information both technical and historical.