Lighting Control
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A brief Overview of Lighting History & Control

Light sources transform other types of energy into visible radiation.

Candles, gas lamps, and other flames use chemical energy. The sun uses nuclear energy. Most modern light sources use electrical energy. Electricity is covered in a different segment. Most sources waste a lot of energy in the form of heat during the process of making light. Flames are extremely inefficient, but for centuries they were the only controllable sources of light.
Torch circa 20,000 BC
Efficiency: 0.1%
Oil Lamp
Oil Lamp circa 400 BC
Efficiency: 0.1%
Paraffin Candle
Paraffin Cancle circa 1853
Efficiency: 0.1%
Welsbach Mantle
Welsbach Mantle 1866
Efficiency: 0.2%
Many theatres have burned to the ground in past centuries due to the efforts of trying to control indoor lighting. Some theaters used intricate gas pipe systems to bring small flames throughout the space for illumination. Many used torches and some use floating candles so that if water was removed from a trough, the candles would be lowered behind a shield which would, in turn, reduce illumination.

Thomas Edison invented the incandescent filament lamp in 1879, and that has been the main basis of sources for home lighting and the entertainment industry. Edison’s lamp has been largely unchallenged until recently. Carbon arc lamps use high current electrical discharges between carbon electrodes, and began being used publicly in 1879. Carbon arcs are still used in high power searchlights and projectors. Developed in 1901, the Cooper-Hewitt mercury arc was a tube using electrical discharge and was an ancestor of modern fluorescent lamps.

Incandescent lamp light seems brighter and is more concentrated than light created by a fluorescent lamp, but it is only about one-third as efficient. A carbon arc is less efficient and less convenient than either fluorescent or incandescent lamps, but it has a physically smaller source and is much brighter.

LEDs are illuminated by the movement of electrons in a semiconductor material and don’t have a filament, making them much more durable and longer lasting than other artificial sources. LEDs are around 4.5 times more efficient than incandescent lamps at producing light, but they are more limited in their intensity. Since the year 2000, the price of semiconductor devices has come down, and the technology had been developing at a very rapid pace. Recently, the first truly effective theatrical-style lighting instruments have started to make their way into the market place, and they will surely continue to be developed.
Incandescent Light Bulb
Incandescent Filament Lamp 1879
Efficiency: 2.0-5.0%
Cooper-Hewitt Mercury Arc
Cooper-Hewitt Mercury Arc 1901
Efficiency: 1.5 - 4.0%

T4 Fluorescent tube
Fluorescent tube 1927
Efficiency: 9.0 - 11.0%

Light Emitting Diode (LED) 1962
Efficiency: 15.0 - 25.0%
Carbon arc lamps cannot be dimmed, and fluorescent lamps are not focused enough to be used well in theatre. LEDs use direct current which traditionally doesn’t dim as gracefully (evenly / smoothly / beautifully) as incandescent sources, but advancements are being made quickly, and high-quality LEDs (with more consistent colors and smooth dimming) are now available at a higher cost.

Incandescent lamps (including tungsten halogen lamps) produce a natural-looking white light (as discussed in the segment on color) and dim smoothly, although as the filament warms up, the light also takes on a warm tint (known as “amber drift”, also explained in the segment on color).
Mercury Arc bulb
Open Arc(predecessor of the above mercury arc) 1878
Efficiency: 1.0 - 2.0%
Xenon Short Arc
Xenon Short Arc began use in 1952.
Example is a 15 kW xenon short-arc lamp used in IMAX projectors

Soon after electric lighting became standard, switchboards were installed in many theaters. Literally a long row of on-off switches, switchboards were usually organized by either illumination area or color wash. Eventually, large resistance dimmers became commonplace. Resistance dimmers had to closely match the load (the amount of total wattage being manipulated) which made their use somewhat problematic, and though effective, they turned the extra power into heat which was not efficient and could be uncomfortable.
resistance dimmer
Resistance Dimmers
Autotransformer dimmers later replaced resistance dimmers because despite being nearly as large physically, they were much more efficient and more flexible. Their load capacity was more independent and did not need to be as closely monitored as resistance dimmers. All of these early dimmers had large, generally heavy handles that were relatively difficult to move which made large or complex fades challenging to achieve.
Autotransformer Dimmers
Autotransformer Dimmers
Before computers were common and inexpensive, lighting operators continued to write cue sheets that had to be implemented “live” in real time, in front of an audience, whenever that cue was called. Slow, gradual fades were difficult, as were very large or complex cue sequences. Designers were often frustrated by inconsistencies and common mistakes made by operators.
Autotransformer Dimmers
Autotransformer Dimmers
A silicon-controlled rectifier (SCR) is a solid state dimmer which switches on and off at an adjustable time of alternating currents’ cycle and does not absorb any of the voltage, allowing it to operate cooler than previous dimmers and were far more efficient. SCR dimmers (commercialized in 1957) could be controlled remotely by means of small, low voltage signals which allowed for the development of what would become modern lighting control systems.
silicon-controlled rectifier (SCR)
Modern Silicon-Controlled Rectifier (SCR) dimmer module consisting of two 2.4k dimmers.

In the early 1960s the two-scene preset board was developed, which was constructed with two sets of sliders (potentiometers) known as banks. Each bank had one slider that represented each dimmer in the system. The sliders in each bank could be set to achieve the desired look on stage. While one bank was “live”, the other could be manipulated without affecting the lights on stage.

Operators could choose when to crossfade from one preset to another, could “split fade” for a blackout, or have both presets active at once, depending on what was necessary for the show. This set up was a huge advancement which meant one operator could run an entire show with accuracy and was no longer required to be in the physical proximity to the dimmers, thanks to a relatively small control cable.
3-scenes worth of a 10-scene preset board
3 scenes worth of controls, as part of a 10-scene preset board.
Photo courtesy of John Barnes.
Preset panels could be employed when a large number of cues needed to be operated quickly. Typically a two-person operation, with one person operating the banks of presets and one operating the control board, there could be as many as 10 different banks (or presets) available upon demand.
3-scenes worth of a 10-scene preset board
John Barnes at the control center of a 10-scene preset board.
Photo courtesy of John Barnes.
Modern 2-scene preset board
More modern 2-scene preset board.
Computer systems store information digitally, but early computerized lightboards continued to use the same 10 V DC control signal that was used in preset boards. One early, popular, computer control board was the Kliegl Performer. It used a parallel port connector as an interface to the dimmers, and its memory could be backed up to a cassette tape.

The modern protocol (communication language) used by most theatrical equipment is known as the DMX 512 which stands for “Digital Multiplexing 512”. It was created in 1986 and is further explained in the accompanying videos.
Many different computerized lighting consoles, available from various manufacturers, have been specifically designed for use in the entertainment industry. Sliders, trackpads and buttons can be programmed to operate one or many lighting fixtures, depending on what’s desired. With the interface designed specifically for lighting designers, these boards are relatively easy to learn because most use our terminology.

Some software packages have been created so that even a standard computer can be outfitted with a USB – DMX pin adapter to control equipment, and even iOS (iPad) apps are starting to appear. Because traditional lighting fixtures are controlled by dimmers which do the “heavy work”, and “intelligent fixtures” use independent power supplies, it is reasonable that any controller which can be outfitted to send a DMX signal can be a viable method for operating lighting during theatrical events.
Software options
A USB-DMX adapter allows one to run lighting control software from their laptop.