Intelligent lighting

A Martin MAC 550 intelligent light

Intelligent lighting refers to stage lighting that has automated or mechanical abilities beyond those of traditional, stationary illumination. Although the most advanced “intelligent” lights can exhibit extraordinarily complicated effects, most lighting technicians agree that it is closer to “obedient” lighting since the intelligence lies with the programmer of the show rather than the instruments or the lighting operator. For this reason, intelligent lighting is also known simply as automated lighting or moving lights.

History

The first remotely controllable lighting system was the Mac-spot, which was retrofitted onto a standard Par64 frame. It offered remote pan and tilt control, but no other features^[1]. The first fully controllable automated light system was originally implemented in 1972, at the State Theater of Basel, Switzerland with a controller that used punched paper tape as the cue recording/playback medium - a cumbersome, but visionary, system which was clearly ahead of its time.^[2] Advances in memory and storage technology in the decade that followed made the first modern computer controlled automated stage lighting system practical in the popular music concert industry in the early 1980s by Vari-Lite, Morpheus Lights and other companies. As automated fixtures gained widespread acceptance in this market they evolved and their capabilities became more refined. These more sophisticated automated fixtures were increasingly used in theatre, television, and other entertainment lighting applications.

Features

Several intelligent lights in use at a concert. Note the white beams they produce

An automated light, properly called a luminaire, fixture or a moving head, is a versatile and multi-function instrument designed to replace multiple stationary lights. Depending on the venue and application, automated luminaires can be a versatile and economical addition to traditional lights because, with proper programming, they can swiftly alter many aspects of their optics, changing the “personality” of the light very quickly. Lighting is typically pre-programmed and played back using only simple commands, although moving heads can be controlled “live” if the operator is sufficiently experienced.

Control

Moving lights are controlled in many ways. Usually the fixtures are connected to a Lighting control console, which outputs a control signal. This control signal sends data to the fixture usually in one of three ways: Analogue (which has largely been phased out), DMX (which is the industry standard control protocol), or Ethernet Control (which is still in development). The fixture then takes this signal and translates it into internal signals which are sent to the many stepper motors located inside.

XLR connectors, the most common method of controlling moving heads. Note that these are 3-pin XLR connectors, which are used by some manufacturers, rather than the 5-pin, which specified by the USITT DMX-512 Standard.

The vast majority of moving heads are controlled using the DMX protocol, usually using dedicated unshielded twisted pair cable with 5-pin XLR connectors at the ends^[3]. Each fixture is assigned a block of DMX channels in one of the venue's DMX universes (a self-contained set of cables and fixtures which can operate a maximum of 512 individual channels). The central lighting desk transmits data on these channels which the intelligent fixture interprets as value settings for each of its many variables, including color, pattern, focus, prism, pan (horizontal swing), tilt (vertical swing), rotation speed, and animation.

Since moving heads did not attain prominence until DMX's predecessor, analogue, had passed the zenith of its popularity, very few moving heads use analogue control (this is also due to crippling restrictions on bandwidth and data transfer speeds). Some of the most modern intelligent fixtures use RJ-45 or Ethernet cabling for data transfer, due to the increased bandwidth available to control increasingly complicated effects. Using the new Ethernet technology, control surfaces are now able to control a much larger array of automated fixtures^[4]. Because many devices can be connected to a single network, these devices have the ability to not only listen to a control signal from a lighting control board, but have the ability to transmit information back to the board and other entities on the network. Now, it is possible for a fixture to self-diagnose any problems, announce itself on a network, or accept setting changes from any place on the network. Because of the digital properties of networks, and its bit-checking abilities, lighting control networks can now safely operate pyrotechnic and rigging devices without threatening the safety of performers and crews.

Moving lights are programmed using a fixture box in ETC light boards

Moving lights are much more difficult to program than their analogue cousins because they have more attributes per fixture that must be controlled. A simple conventional lighting fixture uses only one channel of control per unit: intensity. Everything else that the light must do is preset by human hands (color, position, focus, etc.) An automated lighting fixture can have as many as 30 of these control channels. A slew of products are available on the market to allow operators and programmers to easily control all of these channels on multiple fixtures. Lighting boards are still the most common control mechanism, but many programmers have come to use computer software to do the job. Software is now available that provides a rendered preview of what your stage will look like once you are actually controlling the lights. This allows programmers to work on their show before ever entering the theater and know what to expect when the lights are connected to their controller. These products usually feature some method of converting a computers USB output to a DMX output.

The latest generation of moving heads ^[5] are integrating digital projection capabilities, creating a real convergence between lighting and video projection. These new generation of heads do not only require to be controlled for intensity, position and focus but will require video content control features as well.

Construction

Intelligent fixtures usually employ compact arc lamps as light sources. They use servo motors or, more commonly, stepper motors connected to mechanical and optical internal devices to manipulate the light before it emerges from the fixture's front lens. Examples of such internal devices are:

• Mechanical dimming shutters used to vary the intensity of the light output. Mechanical dimmers are usually a specially designed disk or a mechanical shutter.
• Shutters with high speed stepper motors are used to create strobe effects.
• Color wheels with dichroic color filters used to change the color of the beam.
• Variable, incremental Cyan, Magenta and Yellow color-mixing filters to vary beam color via subtractive color mixing. Using this method, a much wider range of colors can be created than is possible using single color filters^[6].
• Automated lens trains used to zoom & focus the beam; irises are used to change the size of the beam. Some fixtures have as many as 10 independently controlled prisms or lenses to focus and shape the beam ^[7].
• Pattern wheels with gobos and gate shutters to change the shape of the beam or project images. Some fixtures have motors to rotate the gobo in its housing to create spinning effects, or use their complicated lens systems to achieve the same effect.
• Automated 4-blade framing shutters to further shape the beam and control unwanted spill.

These fixtures also use motors to enable physical movement of the light beam by:

• Pivoting an automated mirror which reflects the beam along X & Y axes, or
• Attaching the entire fixture lens train to a yoke with motorized pan & tilt

Note that fixtures which use the former method are not technically “moving heads”, since the light source itself does not move. However, the term “moving head” is used interchangeably throughout this article.

Usage

5 Moving Yokes Lighting up a Mirror Ball

Intelligent lights can be used wherever there is a need for powerful lighting which must be capable of rapid and extreme changes of mood and effects. Moving heads would, therefore, be inappropriate in a setting which does not require strong lighting (such as a home) or where the “quality” of the light required does not vary excessively, although it may need to be very strong for a venue like a stadium). Naturally, there are exceptions to this rule, most notably the use of enormous numbers of moving heads for epic sporting events, such as the Commonwealth Games^[8], where nearly 1000 individual moving heads were used to light the opening and closing ceremonies of the XVIII Games in Melbourne.

Usually, however, the use of intelligent lights is confined to theatre, concerts and nightclubs, where the versatility of these fixtures can be utilised to its best extent. In these applications, the uses of fixtures can be informally grouped into two categories: active and passive (although these are not standardised terms).

Passive use of intelligent lights involves utilizing their versatility to perform tasks which would otherwise require many conventional lights to accomplish. For example, six to eight moving heads can create a textured blue “night” effect on the stage floor while applying amber light to the actors during one scene - this can create a sensation of dusk or night. At the flick of a switch, the moving heads can change to an animated red “fire” effect for the next scene. Attempting this transition with traditional lighting fixtures could require as many as thirty instruments. In this circumstance, the intelligent lights are not doing anything that could not be achieved using “dumb” fixtures, but they dramatically reduce the number of lights needed in a rig. Other features of moving heads, such as rotating gobos, are also possible with conventional fixtures, but are much easier to produce with intelligent fixtures.

The other use of intelligent lights is to perform tasks which would otherwise require human involvement, or be simply impossible with standard lights. For instance, a number of moving heads producing tightly-focused, pure white beams straight down onto the stage (especially if a smoke machine or hazer is used to make the beams visible) will produce a fantastic effect reminiscent of searchlights from a helicopter. To recreate such an effect without intelligent lights would require at least one human operator seated directly above the stage with a followspot, which would be prohibitively expensive and possibly unsafe.

Moving head lights are often divided into profile and wash lights. They vary in use and functions but many companies offer profile and wash variants of the same model of light. Profile lights generally contain features like gobos and prisms, whereas wash lights have simpler optics and a wider beam aperture resulting in wider beam angle, which may be altered by internal lenses or “frost effects”. Wash lights are more likely to have CMY colour mixing in lower models although it is common for top of the range profile lights to have CMY mixing. Profile lights are generally used for their beam effect (usually through smoke or haze) wash lights can also be used like this or as stage wash.

A martin mac 250 entour (profile - top) and mac 250 wash) wash - bottom).

A martin mac 250 entour (profile - top) and mac 250 wash) wash - bottom). Notice the difference in beam characteristics caused by the gobo of the entour and the wider beam angle of the wash.

Debate

• Not all the light fixtures that have movement can be defined as intelligent. Basic club lighting is not controllable other than basic on and off. This lack of features makes them just a small step above a conventional Stage lighting instrument

• Moving mirrors are faster than moving head fixtures. However moving heads are visually more interesting, and have a far larger range of movement.

References

1. ^ http://www.mts.net/~william5/history/hol.htm - scroll down to "Early Automated Lighting" ~1970
2. ^ Cadena, Richard (2006). Automated Lighting. Focal Press, 11–12. ISBN 978-0-240-80703-4. 
3. ^ DMX512 Control Protocol Information - Connectors and Cables
4. ^ Cadena, Richard (2006). Automated Lighting. Focal Press, 56–58. ISBN 978-0-240-80703-4. 
5. ^ Barco | Barco’s digital moving luminaire tears down boundaries between projection and lighting
6. ^ Cadena, Richard (2006). Automated Lighting. Focal Press, 253–254. ISBN 978-0-240-80703-4. 
7. ^ Product - MAC 2000 Profile
8. ^ Casestory - XVIII Commonwealth Games, Melbourne, Australia

See also

• Stage lighting instrument

External links

• Moving-lights - repository of technical info

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