are still the most common control mechanism, but many programmers use computer software to do the job. Software is now available that provides a rendered preview of the output produced by the rig once fixtures are connected to the program or console. 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 computer’s USB output to a DMX output.

The latest generation of moving heads are integrating digital projection capabilities, creating a real convergence between lighting and video projection. These new generation of heads do not only require intensity, position and focus control, but will require video content control 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 can be 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.

Automated lens trains used to zoom and focus the beam; irises are used to change the size of the beam. Some fixtures have as many as 10 independently controlled prisms and lenses to focus and shape the beam .

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 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 either:

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 oving heads, since the light source itself does not move. However, the term oving head is used interchangeably throughout this article.

Usage

5 Moving Yokes Lighting up a Mirror Ball

Intelligent lights (now commonly referred to as automated), 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 uality 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 large numbers of moving heads for international sporting events, such as the Commonwealth Games or Olympic Games, where many thousands of separate automated fixtures are often used to light the opening and closing ceremonies. The 2008 Summer Olympics, in Beijing, had a rig of around 2,300 intelligent fixtures which is “the largest single automated lighting system ever assembled for a single event”

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 automated lighting 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 ight 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 fixture can change to an animated red ire effect for the next scene. Attempting this transition with traditional lighting fixtures could require as many as thirty instruments. In this circumstance, the automated fixtures are not doing anything that could not be achieved using conventional fixtures, but they dramatically reduce the number of lights needed in a rig. Other features of automated fixtures, such as rotating gobos, are also possible with conventional fixtures, but are much easier to produce with intelligent fixtures.

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

Active use of automated lights, suggests that the luminaire is used to perform tasks which would otherwise require human involvement, or be simply impossible with conventional fixtures. For instance, a number of moving heads producing tightly-focused, pure white beams straight down onto the stage will produce a fantastic effect reminiscent of searchlights from a helicopter (especially if a smoke machine or hazer is used to make the beams visible). 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 generally be considered to be too expensive for such a small effect.

Moving head fixtures are often divided into spot 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 rost effects. Wash lights are more likely to have CMY colour mixing although it is common for high-end spot lights to have such features too. Spot units are generally used for their beam effect (usually through smoke or haze) and the ability to project texture, whereas wash lights tend to be used for providing a stage wash.

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. The movement from mirror lights tends to be rectilinear, because the centre of movement for both axis is usually in the same place, while one axis of a moving head luminaire describes a circle (usually called “pan”) and the other (the “tilt”) changes the diameter of the circular movement. In early luminaires a pseudo rotating gobo effect could be achieved by moving the tilt in line with the other axis and then moving the pan from end stop to end stop.

References

^ http://www.mts.net/~william5/history/hol.htm – scroll down to “Early Automated Lighting” ~1970

^ DMX512 Control Protocol Information – Connectors and Cables

^ Cadena, Richard (2006). Automated Lighting. Focal Press. pp. 5658. ISBN 978-0-240-80703-4.

^ LeMaitre FireCtrl Device,An example pyrotechnic control device that can accept RJ-45 control.

^ Barco | Barco digital moving luminaire tears down boundaries between projection and lighting

^ Cadena, Richard (2006). Automated Lighting. Focal Press. pp. 253254. ISBN 978-0-240-80703-4.

^ Product – MAC 2000 Profile

^ Casestory – XVIII Commonwealth Games, Melbourne, Australia

^ MA Lighting On Beijing Olympics 2008

^ Martin Lights Beijing Summer Olympic Games

See also

Stage lighting instrument

External links

Moving-lights – repository of technical info

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