This rough guide looks at the different functions of fixture personality files, trends in complex lighting control interfaces and asks “When is standardisation going to replace fragmentation in the world of stage lighting control?”

Fixture Personality Basics

Intelligent lighting equipment that requires multiple parameters of control has a model specific map of how those functions are controlled. If a fixture requires 30 channels of control, perhaps the first channel is mapped to Intensity with Pan Coarse on channel 3. The other 28 channels all have their own functions including colours, shutters and focus.

The table of channel control functions is not only manufacturer and model specific, but many fixtures also sport a number of control modes that can alter the mapping. Maybe Mode 1 uses channel 4 to control Tilt, while in Mode 3 Tilt appears on channel 3.

The way control channels, commonly DMX addresses, affect the parameters of a specific fixture type is basis of the Fixture Personality.

How do we use Fixture Personality data?

Using a simple DMX preset style desk, knowing the personality of a certain fixture tells us which faders the different attributes. So, we know that fader 1 will control Intensity, for example. But who wants to control complex lighting fixtures using a preset desk? Not me.

Every intelligent lighting control needs personality data to function properly. At it’s simplest, the console needs to know how to assign control channels to the different parts of the desk – Intensity to faders, Pan and Tilt to the position controls etc. When you select Gobo control, it’s no good finding the encoders are adjusting Prism.

So, the console needs to know the personality of the fixture types and these are commonly stored in a library of Fixture Personality files and set during the desk patching process. Currently, fixture personality file formats are proprietary to the specific console manufacturer. This bugs me but more about that later.

Other Fixture Personality File Data Use

So far, we’ve looked at the way a fixture personality file is used to map the different control channels to the interface of the console. This is only a part of it’s use.

Range table data – Some attributes of an intelligent fixture perform different actions depend on their set channel level, for 0 to 255. While parameters such as dimmer, pan and tilt change on a linear scale based on level setting, other parameters such as gobo or colour wheels have set positions that clunk through based on a range of control level. The Open White slot in a colour wheel might be recalled by Colour Wheel 1 > Level between 0 – 17. If your console fiddling experience is to be a positive one, the desk needs to know this.

Control channels can adjust some varied functions depending on range of channel level. Perhaps the macro to Lamp Off the fixture is fired using a Shutter > Level between 220 to 255, you don’t want this happening by accident but you do want to be able to Lamp On using the pre set macro at the console. Range table data within the fixture personality file sorts this out.

Auto Palettes – Patching up a new set of fixtures, you ask the console to generate some standard palettes to get started. White, Red, Amber, Gobo 1, Gobo 2 the list goes on. Using the range table s and other personality file data, the console is able to speed up the building of the blocks by automating some of the process.

The Future of Personality Files

While we are still working with a system that uses a Control Channel / Channel Level and different lighting fixtures exist in the market, fixture personality files will continue to evolve. The latest generation of top end lighting consoles have developed some clever techniques such as integrated colour setting whether CMY, RGB or HSB and Fixture Morphing (attempting to exchange one make of fixture for another with losing your programming). Many of these functions rely heavily on even more advanced fixture personality files and the processing of that data.

This brings me to a personal bug bear of mine.

Anyone who knows me well will know that I have been banging on for years about the benefits of standardising fixture personality files. Here are some of my beefs with the currently proprietary personality formats:

• Not portable between platforms like consoles and visualisers.
• They take console makers valuable time to create. This can makes the personalities released poor quality, with errors and omissions in functionality.
• Fixture makers can change mapping and mode specs. More time spent updating files for every desk maker.
• New fixtures are being added to the market at a furious rate. Every CheepoSpot fixture needs a personality file for the four guys in the world that use the darn things.

The whole thing is so inefficient – why are we creating hundreds of different file types for different consoles and software when the fixture manufacturer could create one – just one personality file. And the correct one. And update it when they changed their firmware. Having proprietary personality files just seems like such a waste of everyone’s time.

Will it ever happen? Will the industry unite around some kind of XML personality file that will fulfil the needs of the simplest control desk and the worlds biggest lighting console?

The lighting business has agreed on DMX512 and the ARTNet protocol is one of a number of widely adopted standards that have been integrated into control equipment. The current mess is the confusion between different media servers and two way communication with different consoles. Getting media thumbnails displayed and other vital tools. But there may be hope on the horizon.

In reality, once one feature has appeared on one console it soon filters down to other makes BUT it is then implemented in each desk makers own “special” way. Let’s face it, the output of a lighting console ends up the same, no matter what gubbins gets between the human and the fixtures. The console makers are only really selling the interface, after all. Surely the differentiation between control only needs to be the interface and the level of functionality

The trouble with an ever more fragmented lighting control market is everyone is so busy trying to differentiate their own product that it sometimes seems like we are getting further from standardisation and away from efficient development.

As each console relies on increasingly advanced personality files, hopes of an integrated standard single file for fixture personality data seems to get further away?

Perhaps the next generation of lighting technologists, the On Stage Lighting readers, will take on the challenge of better standardisation in future lighting control. If you are keen, you might like to take a look at the details of ESTAs ACN (Architecture for Control Networks).

OK, so we’ve taken a quick tour of fixture personality data and you’ve waited patiently while I had a minor rant about standardisation in entertainment technology. Oh, and we have spotted the ACN cavalry far off in the distance. Hopefully, you will have a bit more of an understanding of another vital tool in modern stage lighting – fixture personality data.

With any luck, future development and adoption of ACN will sort out the communication of individual fixture personalities (assume somthing like an XML file), but in the meantime we are stuck with fixture personality files for a while yet.

If you have any thoughts on how the lighting industry should emerge from the sheds and into the 21st century world of development, put your comments in the box below.

Image by Samuel Stroubes

If this has helped you, consider buying me a beer and CLICK HERE to donate a few bucks to On Stage Lighting (why should I donate?). Thanks, - Rob

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The first in a series of articles about using modern intelligent lighting. This beginner’s guide to the moving light looks at common lighting effects and what’s inside the fixture itself.

When I started working with moving lights, the technology was fairly new and extremely mysterious. Now they have become cheaper, it seems like everyone had got access so some kind of intelligent light. Lighting techs are the kind of people that, given the chance, will rip the covers off any kit quicker than you can say “Leatherman”. But what if you are just starting out in lighting and don’t have access to any intelligent gear?

What’s Inside a Moving Head?

Let’s look at what a moving head can do and the technology inside.

Light Source – Bright, efficient and even.

The light source in a moving head needs to be bright and efficient. Normal tungsten stage lighting lamps don’t fit the bill, so an arc lamp is used. Arc lamps require a special power supply (part of the fixture) and light source is not dimmable. Discharge lamps also generate a lot of heat and UV radiation – these are controlled by shields in the lamp housing. A reflector rounds up the photons and points them in the right direction.

Dimming / Intensity – Fading.

Stage lighting needs brightness/intensity control – dimming, if you like. Because the lamps (bulbs) in most moving lights can’t be dimmed electrically, a mechanical method is used. The dimming shutter on a moving head is simply a motor driven, metal mask that gradually cuts down the light output. Dimming shutters are mounted as far from the light source as possible, at the “front” of the head.

Strobe Shutter – Fast moving on/off switch.

Most moving lights also have a second shutter for strobe control, the rapid on/off action . The shutter strobe doesn’t dim, it just cuts out light. Very quickly.

Focus and Beam Control – The useful stuff that gives you control over the light output.

Even a 500w fresnel has some beam control, it’s what makes it useful. Moving spot fixtures have focus (sharpness) and/or zoom (bigger/smaller) functions, controlled in the usual manner – moving lenses. Spots also have Iris capability and some contain beam shaping shutters, which can cut off and angle edges remotely. Clever stuff.

Moving Wash or Beam lights (waggly PAR cans) give you the useful characteristics of a PAR lamp, beam width and oval angle (similar to spinning a normal PAR). These effects are created using glass frosts and adjustable brushed silk wheels within the fixture.

Colours – Changing colours without getting up a ladder

There are two kinds of colour control available in moving lights. Fixed colours and variable colour mixing. The two systems have pros and cons and many intelligent fixtures use both systems.

Fixed colour – Produced by one or more rotating colour wheels within the fixture. The light is filtered through special dichroic glass plates to produce the colour. Fixtures with 2 fixed colour wheels can overlay 2 dichroics, making a new colour using subtractive colour mixing. The advantage of fixed colour is that it provides good saturated colours such as Red and Dark Blue. The downsides are the limit to the number of colours available to the lighting designer. With a moving light “in view” (ie, on) the colours “clunk” don’t fade into place but clunk, often running through unwanted colours in the wheel.

Colour Mixing – A wide range of colours are produced using variable CMY subtractive colour mixing. Three gradiated colour “flags” are controlled to filter different amounts of the secondary visible light spectrum. The three colours Cyan, Magenta, Yellow when mixed in different quanties make a wide range of useful colours that can be faded into place. The down side to CMY colour mixing is there is some saturated colours it just can’t do.

Gobos – Old technology, great effects.

Gobos are still a great stage lighting effect and moving spot lights have gobos built in. One or more gobo wheels are hidden away inside, some rotating. A fixed gobo wheel is simply a large rotating plate with the gobo patterns punched around it. Rotating gobos are mounted in a more complex wheel that “indexes” (rotates) the gobo, as well as slotting a new one into the path of the beam. The gobo mechanism on a moving light is situated near the focal centre (the gate) and two gobo wheels can be laid on top of each other to get some interesting effects, especially with the focus function.

While there are many moving lights with “old fashioned” metal gobos inside, there are more advanced gobos around. Many are etched glass or dichroics that make coloured pictures possible, as well as much more intrictate designs. More slides than gobos, really.

Prisms and other Effects – With all that lot stuffed into a small casing, it’s a wonder there is room for more. Prisms that split the light into multiple beams, FX wheels and other bits and pieces. These lighting effects are based on traditional methods in stage lighting, automated and put into a moving head. Again, a relatively simple formula of motor driven moving parts.

What about actually moving this Moving Head, eh?

Ok, so you got to here and wondered why we hadn’t talked about this intelligent lighting actually moving. Well, I don’t know what to tell you. It moves. One motor makes it go side to side, the other motor up and down. The man on the street has gotten used to seeing waggly lighting, beams moving around doin’ stuff. “Robotic” lights are no longer interesting just because they look like magic. However, being able to direct a moving head to different points in space or make dynamic pictures in the air is powerful tool in your armoury.

So, now I know all about moving lights?

To use intelligent lights, you need to know what a moving head can do and how. As a user or operator, understanding the mechanics will enable you to get the most out of the equipment, the image at the top shows a reeded glass gobo, prism and colour given the soft focus treatment. All the little wheels, motors and bits of glass inside grind away inside creating looks that can be magical on the outside.

In the next part of the series, we will have a look at the more technical mechanics of a moving head with some pictures. If you have any questions or comments about this basic guide to moving heads, put them in comments box below.

If this has helped you, consider buying me a beer and CLICK HERE to donate a few bucks to On Stage Lighting (why should I donate?). Thanks, - Rob

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• Moving Light Control – Palettes – Lighting Desk Basics 4
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