Written by Jon Primrose – please send comments / requests for additions to me via the Contact Us button above.
Any lighting system consists of the following parts:
- Rigging Positions – these can be permanent lighting bars or portable setups (see below)
- Lanterns – these (sometimes called ‘lights’, incorrectly, in my view) contain a lamp, a reflector and (usually) a lens. The beam can be adjusted on most lanterns to change the size of the beam.
- Cables – these supply power to the lanterns, and may be built into the lighting bar (internally-wired bar) or can be temporary, running around the edges of the space to a portable stand or along a lighting bar.
- Dimmers – these large boxes are usually permanently installed in a store or cupboard adjacent to the stage and deal with the business of producing the electrical supply for each lantern. Each dimmer has a fuse or circuit breaker protecting it, and if you can’t get a particular dimmer to work, that’s the first thing to check.
- Control Desk – The control desk is connected to the dimmers via a DMX cable (stands for Digital Multiplex). This control signal can deal with up to 512 dimmers, so is properly named DMX512. There are many different types of control desk, from fully manual to state-of-the-art computerised versions.
More information on each part of the system can be found below.
Permanent, fixed lighting
A permanent system usually consists of a number of scaffolding bars mounted to the ceiling or walls of the room to form the lighting rig. If the bars contain numbered sockets for stage lanterns to be plugged into, they’re known as ‘Internally-Wired Bars’ or IWBs.
If the system is correctly designed, the number of cables that have to be run around the lighting rig should be very small. Lanterns are plugged into their nearest socket.
The internally wired bars are then connected to a patch panel (consisting of a row of numbered plugs) which connect into the dimmer racks which are usually positioned above the patch panels. The dimmer racks are connected to industrial-type power sockets which give them enough power to run all of the necessary lanterns, and to a control connection from the lighting desk. The lighting desk can be positioned anywhere around the space, and is plugged into the dimmer racks using a DMX512 control cable.
Access to Permanent Lighting Rigs
This seems to be a major issue in many schools. There are many health & safety restrictions in place, which are currently preventing learners from making full use of the stage lighting rig.
For this reason, the best plan is to use portable temporary lighting equipment. There are, ironically, more safety hazards and chances of things going wrong with a portable system, so please take care to read and understand the following section.
There are a few solutions which make using permanent lighting rigs usable in schools.
The most expensive option is to reinstall the lighting bars so that they are on motorised winches. Cable management systems (such as the Jacobs Ladder system shown in the video below) exist which mean the lanterns can remain plugged in and connected to the dimmers when the bar is at rigging height (around 3 feet above the stage floor).
Learners (and staff) can then safely hang the lanterns on the bars, plug them in, colour them and even give them a rough focus, and check they work, before raising the bar up to working height.
To focus the lanterns, you’ll still need to get up to rig height, but this is considerably safer than having to rig them at height.
Many schools seem to use scaffold towers for this operation, but these can only be assembled by a suitably trained member of staff (or, more likely, an external contractor). A scaffold tower should not be kept at the school for this purpose – there are too many chances to make errors when assembling it.
A purpose-built mobile access platform such as the Esca range is the way to go.
Additionally, Moving Lights can be used to replace some of the fixed lanterns in your rig both above the auditorium and above the stage. These can be controlled by a modern computerised lighting desk, and (after an initial learning curve) are straightforward to use. See Moving Lights under Lanterns (below) for more information.
A portable system consists of a number of lanterns which can be rigged (set up) on telescopic stands at floor level. This avoids the need for access platforms and working at height, and can still produce excellent results.
It may be possible to use a portable system in conjunction with the permanent rig. The rig can provide a basic general wash (possibly using two colours – a warm and a cold gel) and the portable system can provide any ‘special’ effects or colours.
- Telescopic Lighting Stand
- T Bar
- Dimmer Pack
- Control Desk
Information coming soon. For the moment, see Types of Lanterns
Fresnels / PCs
- Check lantern for any visible damage, especially around the cable. Any damage to the cable sheath should put the lantern out of service to get repaired.
- Prepare the lantern. Make sure it has a safety bond attached and that any accessories are present (e.g. barn doors for a Fresnel or PC, shutters for a profile). Make sure the cable is free hanging and not wrapped around the lantern. Undo the hook clamp bolt.
- Hang the lantern on the bar in the correct position (assuming the bar has been lowered to floor level). All of the hook clamps should be around the same way.
- Tighten the hook clamp.
- Roughly point the lantern in the direction it will be focussed.
- Secure the safety bond around the bar.
- Plug the lantern into the socket.
- Open the barn doors (Fresnel or PC) or pull the shutters out to open position (Profile).
VIDEO DEMONSTRATING THE ABOVE – COMING SOON
Lighting with LEDs
LEDs are revolutionising the stage lighting world. They require a different method of connection so your lighting system will need some modification to make it easy to use them.
A traditional lantern is plugged into a dimmer. However, an LED lantern must not be connected to a dimmer. It requires a constant undimmed power supply. It also needs a DMX512 connection, from the lighting desk.
DIAGRAM SHOWING LED CONNECTION, INCLUDING WAYS OF CONNECTING DMX512 – COMING SOON
Although they are far more complex than standard lanterns, moving lights can save vast amounts of time, and can also solve the problems of access to fixed lighting bars mentioned above.
Wash Lights – A soft-edged pool of light is produced, similar to that from a Fresnel
Spot Lights – A hard-edged spot of light, similar to that from a Profile. Gobos can also be used in spot lights.
Older moving lights use discharge lamps, which remain on all of the time the unit is switched on. More current moving lights use LED light sources which are far more energy-efficient, and also offer a wide range of colour possibilities.
As with fixed LED lanterns, moving lights need a constant undimmed power supply, and a connection to the DMX512 signal from the lighting desk.
DIAGRAM SHOWING MOVING LIGHT CONNECTION – COMING SOON
There are two types of cables in UK-based lighting systems;
15 Amp Cables (also sometimes known as TRS)
These cables are terminated with 15 Amp round-pin plugs and sockets, and have been the standard in UK theatres for many years. In some TV studio situations, the newer 16 Amp plugs and sockets may be used, but these are bulkier (and more fragile) than the 15A version. TRS stands for Tough Rubber Sheath, and describes the cable, so it’s not strictly the correct abbreviation for any type of cable with connectors on…
photo coming soon
These control signal cables carry a data signal from the control desk to the dimmers, but are also used to send control information to LED fittings around the rig and also to any moving lights or other effects units you may be using.
They are terminated with 5 pin XLR connectors usually, but can also be used with 3 pin XLR connectors (as the DMX standard only uses 3 pins). While microphone cable can sometimes be used to carry DMX signals it isn’t good practice as the signal is more likely to develop faults if it’s not carried over the correct data cable.
DMX Terminators should be used at the end of a run of DMX cable.
photo coming soon
The permanent dimmers are an important part of the electrical installation, and should be maintained regularly.
- Know the maximum power you have available. There should be plenty of power available in school, but this isn’t always the case. How do touring lighting technicians deal with the amount of electricity available? Could the lighting rig be run from a single socket in a house? Why not? This can be a useful exercise for the class – to calculate how much electrical power is needed for a particular stage lighting setup. How does this compare to the amount of electricity used in a typical house in a day? (Maybe this is a chance to collaborate with the science department).
- Make sure you know where all of the socket outlets are around the drama space(s). They should all be numbered, and this should correspond with the dimmer numbers. Do a sketch of the space and have this available to save time when working on a new lighting layout.
As well as the permanent installed dimmers, you should try to have a couple of portable dimmer packs available. These can be really useful in class, and mean you don’t need to get the lighting desk every time you want a couple of lights on.
Most modern lighting desks can operate in three ways;
- Manual – each dimmer is controlled by a separate fader on the control desk. Very easy, but complex changes are tricky, and mistakes are common.
- Submasters – each fader can be set to be a whole lighting state. So if your show needs 4 states (warm general wash, downstage spotlight, blue state, stage left side only) then the whole show can be run off just 4 faders. The states can be brought up manually in any order, and at any speed.
- Memory – lighting states are programmed in show order as memories into the desk. The show starts with Cue 1, and each lighting state is a different cue. Very easy to operate, and the lighting is exactly the same each performance. But it’s the most time-consuming way of programming, and is least satisfying for the operator during the show.
MORE TO FOLLOW
Software Lighting Control