Theatrical lighting – introduction

By | January 24, 2016

There are many different aspects of lighting in a public space – so many in fact that even seasoned technical crew can be confused. This article offers and introduction to the different lighting systems you might find in a performance environment.

Consider a traditional small theatrical venue. The venue has public spaces and non-public spaces. Public spaces include the foyer, bar, coffee lounge, cloakrooms and toilets and (of course) the auditorium. Non-public spaces may include offices, store-rooms, technical areas, workshops, rehearsal rooms and of course the stage and its environs.

From a performance point-of-view, public or non-public areas in front of the stage are called front-of-house (FOH) and areas behind the stage are called backstage. The stage stands alone.

During the course of a-day-in-the-life of a theatre many different lighting systems come into play. But before we get into details, we need a few definitions:

Luminaire – the technical term for a light-fitting used to facilitate and direct the light from a lamp to illuminate the environment. Signal lamps are not generally called luminaires. Amenity luminaires are often referred to as lights, fittings or fixtures; performance luminaires are often referred to as lanterns.

Lamp – the actual device which converts electricity to light. A lamp is installed in a luminaire.

Luminous efficacy – the technical term for efficiency of a lamp and measured in lumens per watt. However, if we are considering a luminaire comprising a lamp and some control gear it is usual to refer to the luminaire’s efficiency.

General amenity lighting

Amenity lighting is provided to enable people to see and move around in their environment. Amenity lighting may be functional and/or decorative. Decorative or mood lighting typically provides a better emotional experience at the expense of efficiency.

Amenity lighting is deployed in all general public and non-public spaces controlled either locally, by central switch clusters or by a building management system (BMS).

Local switching is as domestic lighting – the light switch is adjacent to the door when you enter a space.

Clustered switching is where all of the lights in a particular zone are switched from a switch-bank which may have up to (say) twenty four switches. For example, there may be a switch bank behind a bar which controls all the lights in the bar area, the lounge, and the toilets. This arrangement serves both to allow switching on and off all the lights centrally (so the bar staff knows they are on or off without having to walk around to check) and to prevent public interference.

Building management systems may be programmed with timed schedules and incorporate daylight detectors and occupation sensors to control lighting automatically.

Emergency lighting

Emergency lighting is provided to enable people to see their environment during a power cut; to direct them towards emergency exits, and to indicate which exits should be used.

Emergency luminaires may be stand-alone or may be part of a central battery system. Emergency amenity lighting may be integrated into the general amenity lighting system or may be separate. Generally for each emergency luminaire or local cluster of luminaires there will be a test switch (called a secret-key grid switch) to simulate a power cut and cause the emergency light to illuminate on battery power. Each emergency light must illuminate for a certain minimum period of time (measured in hours) without mains power.

There are three types of emergency fitting:

Non-maintained fittings – only illuminate when there is a power cut – in which case they remain on until the batteries are exhausted. Otherwise they are off.

Maintained fittings – illuminate if there is a power cut; may illuminate if there is not a power cut.

Maintained fittings may have one or two mains feeds. If they have a single feed, they will be on if mains is present. If  they have two mains feeds then one is a permanent live to charge the batteries (and indicate a power cut) and the other is a switched-live to indicate whether the lamp should be lit when mains power is good. If there is a power cut, the lamp will light (regardless of the switched-live status) and will run on batteries until the batteries are exhausted. Usually, maintained fittings will be brighter when running on mains power than running on batteries.

Sustained fittings – a combination of a general amenity fitting and non-maintained emergency fitting. Such fittings require two feeds – a permanent live to charge the batteries (and indicate a power cut) and a switched-live to power the electrically-separate amenity lamp. Again, normal amenity operation will likely be brighter than emergency operation.

Display and decorative lighting

General areas may have display and or decorative lighting as-well-as or in-lieu-of general amenity lighting. Such lighting is designed to create a specific atmosphere or provide spot-lighting for particular displays and/or pictures on the walls. It is usually locally-controlled and is often switched separately from amenity lighting so that it may be switched off when the building is not in public use.

Cleaners’ lights

Separate cleaners’ lights may be deployed for two reasons: Firstly because an area’s amenity or decorative lighting is not adequate for cleaning purposes and/or secondly, because cleaners may not have access to the controls for the usual amenity lighting.

Auditorium Lighting

Audience lights or house lights – Usually referred to as ‘house lights’, these are decorative and usually dimmable lights which are used for amenity lighting before and after a performance. For a performance they are typically controlled from the lighting box, although they may also be controlled from the stage-manager’s desk and sometimes there is a front-of-house control as well. The lighting operator will normally dim these lights slowly before a performance and return them to full during the interval and when the performance is finished.

Gangway lights – Late arrivers and people needing the bathroom will need to see the gangways and stairs when the house lights are dim. In very small venues, there may be ushers with torches (flashlights) to assist people moving around during a performance. However there may be specific gangway lighting installed – usually as part of the emergency lighting system.

Emergency amenity lighting – Emergency amenity lighting will generally be separate to the dimming house lights and will typically be non-maintained.

Emergency exit lights – the auditorium will have maintained emergency exit lights. It is usually not acceptable to turn off the emergency exit lights – even if there is a “compelling artistic need” to do so.

Cleaners’ and/or working lights – In many auditoria the house lights are not bright enough (even when on full) to provide adequate amenity lighting for cleaning and maintenance. Also, there may be an efficiency issue (decorative lighting can be comparatively expensive to run) or an access issue (cleaners may not have access to the house light controls). In either case it is usual to provide additional luminaires for cleaning and maintenance activity. These luminaires will not be used for performance.

Performance lighting – See separate section below.

Follow spots – Follow spots are considered part-of the performance lighting system. Again, they are not used for any other purpose than lighting a show.

Orchestra pit lighting – Amenity lighting and illuminated music stands may be remotely controlled as part of the performance lighting or a separate channel on the house lighting as there is sometimes an artistic requirement for blackout in the orchestra pit during part of a performance.

Round stage blues/whites – See stage lighting section.

Stage Lighting

For our purposes, we are imagining a conventional proscenium-arch theatre with a house curtain. The stage area is therefore the area behind the proscenium out to the back and side walls (i.e. the area visible to the audience if no set, scenery, masking, drapes or cyclorama is deployed).

General amenity lighting – See working lights below.

Emergency lights – Emergency amenity lighting will be non-maintained and will often be part of the emergency exit lighting system. Emergency exit fittings will usually be maintained and will therefore require masking from the audience.

Working lights – General amenity lighting will take the form of working lights – which are often outdoor-style flood lights affixed to the performance lighting bars. Working lights are usually switched from the stage-manager’s desk or close by. Working lights are always extinguished during a performance.

Performance lighting – See separate section below

Round stage blues/whites – It is usual to have some sort of low-level (i.e. fairly dim) lighting behind the set to act as amenity lighting for performers and stage-hands who are moving around the area on stage but behind the set. This lighting traditionally takes the form of fluorescent strip-lights some of which are white and some of which have a deep blue gel wrapped around the tubes (there are modern ways to do this with LED lighting of course). The rule generally is that if the house curtain is up the lights must be blue (i.e. dimmer, less obtrusive). Before and after the show and between acts when the house curtain is closed, the lights may be switched to white (brighter, better colour rendering). These lights are switched from the stage manager’s desk or close by.

Round stage blues/whites may be deployed anywhere performers or stage-hands need to move around or work while there is a performance on. Locations may include the fly rail, on-stage dressing rooms, catwalks, follow-spot positions, orchestra pit, under-stage (if there are stage lifts or traps), etc.

Performance Lighting

Mains power circuits may be categorised as dimming, non-dimming, independent, independent contactor or permanent live.

Dimming, non-dimming and independent circuits are supplied from the dimmer rack and controlled from the lighting booth at the lighting desk (or board or console).

Independent contactor circuits are also remotely controlled from the from the lighting booth but are entirely separate from the dimmer rack/lighting desk.

Permanent live circuits are connected directly to the electrical installation and are not remotely controlled.

Performance luminaires fall neatly into one of two categories:

  • Those which dim when the power supplied to them is varied
  • Those which require full power and are controlled by DMX

It has become increasingly important to power DMX-controlled luminaires separately from the dimmer system because a lot of luminaires take some time to warm-up from when power is first applied and might be damaged if inadvertently dimmed. Also, dimmer channels are comparatively expensive.

There are a number of ways we can power a DMX-controlled device:

  • Plug the device into a permanent live outlet and don’t turn it off.
  • Plug the device into a permanent live outlet and physically walk up to the device to switch it on/off for every performance.
  • Remotely switch the outlet from the dimmer room.
  • Remotely switch a group of outlets using a large load-switch in the dimmer room.
  • Remotely switch a group of outlets using a motorised-MCCB in the dimmer room (controlled locally or from the lighting booth).
  • Install an independent contactor rack alongside the dimmer rack (controlled locally or from the lighting booth).

The one thing you should not do is use MCBs in the distribution board to turn circuits on or off – they are not designed to regularly switch circuits on-load.

In the next article, we will discuss independent power control further.  svfavicon.png


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