Lighting Basics

From EUTC Wiki


Without rigging, lights are almost useless in the sense of theatrical lighting design. It is the most physical part of theatrical lighting and potentially the most dangerous as it involves work with weight at height. It is made even more dangerous in the Bedlam as most rigging is done at well after normal peoples' bedtimes and sometimes well into the early hours.

Use of Ladders: Rigging in the Bedlam should always be done by ladders from the auditorium floor or stage. For work in the auditorium extendable ladders should be used, always footed by a competent person. Ladders should be leaned against the grid bars, never against trunking or any other attachments to the grid. Only use ladders if you feel confident working at such height. If in doubt, leave it to someone with more confidence. Whilst working on the ladder be careful not to over-extend yourself and at all times be aware of those below you.

Means of Rigging: Before rigging a lantern you should preferably check that the lantern is electrically and mechanically safe. Plug the lantern into the dimming channel on test mode to check the lamp and visually check that the plug and cable are in good condition. Also check that the yoke assembly is functional and that no parts are missing or damaged. Should you see any problems with the lantern at all, report it to the Technical Manager and under no circumstances rig the lantern till the faults have been repaired. The reason for checking the lantern before rigging is that it is far easier to fix faults on a work bench than above your head on top of a ladder.

To rig a lantern on a bar you should:

  1. Place the hook clamp over the barrel and tighten the wing nut on the clamp
  2. Attach the safety chain or bond around the bar. This is an important safety feature used in case the hook clamp fails
  3. Ensure that the bolt and nut attaching the lantern to the clamp are tight
  4. Connect the lantern to the required circuit on the rig, ensuring that the plug and socket are fully mated
  5. Ensure that the lantern is burning the correct way up. This is to maximise the life of lamps as they are designed to burn in a specific orientation
  6. Open any barn doors or shutters that the lantern may have

Rigging onto pipes (vertical bars) is similar to rigging on the grid, but you must ensure that the lantern is not on its side. To achieve this a bar or boom arm may need to be rigged to attach the lantern to the pipe.

Pipes can be rigged in the stage cupboards with the help and approval of the Technical Manager. it is possible to rig bars and pipes in other areas of the theatre. However, speak to the Technical and Theatre Managers before planning to do so, so that it can be ensured that the proposal is both safe and complies with the terms of our licence. All pipes rigged out of contact with the main rig must be earthed.

Cabling: Without power a lantern is near enough useless. Power is supplied to the lantern by means of either being plugged into a circuit on the rig or by means of a 15A TRS cable. If the lantern is on the rig, plug it into a circuit and note the number. Tape any excess cable to the rig with PVC electricians tape (referred to herein by its tech name of LX) allowing enough slack so that the lantern can be focussed.

If the lantern is on a pipe or on a floor stand then a TRS cable must be used to supply power. Ensure that the extension cable is of good condition. The cable must be supported by using LX and any cable on the floor must be taped to the floor using gaffer tape.

Power Supply and Control of Lanterns

Patching: Each channel in the dimming is assigned to a channel of the LX desk. Each circuit on the rig has a tail at the dimming which can be plugged into the dimmers completing the circuit. Then, when switched on, the LX desk can control the intensity of each lantern individually between zero and full intensity.

DMX: The Bedlam lighting system is controlled by means of a digital control system known as DMX. Each dimmer rack is connected in series by means of a multicore cable, each dimming channel having a unique individual DMX address. This means that all the control information can be sent down one cable from the control desk.

Lighting Control Desk: See Lighting Desk