This article looks at special considerations when using LED colour mixing fixtures, why they don’t always behave as you would expect and why photography (and photographers) can be hard work with your LED stage lighting. This is not a physics lesson – more of a lampie explanation in a muddy field at 2 in the morning.



In our colour theory article, we looked at simple principles of reflected colour . Advances in coloured LED technology, interest in saving energy and our downright “techieness” has led to the increased use of LED colour mixing fixtures for stage lighting.

This particular technology comes with it’s own set of issues around dimming and colour. If mixing Red, Green and Blue LED’s is supposed to create 16 million odd colours, why do you get some weird colour results from costumes and sets? More the point, why do I keep getting accosted by photographers and camerapersons (?!).

Colour theory again.

Colour Perception

Without boring you with endless graphs about spectrums, let’s look at the broad priniciple of seeing colour. A normal human eye can percieve light wavelengths of the visible light spectrum ( around 380nm to 740nm) that, as displayed on a spectral graph, creates a nice friendly looking curve.

The CCD in a digital camera can detect visible colour ranges, but it’s spectral graph is a bit different. Digital cameras in particular can struggle with certain saturated colours, even with the “correct” white balance.

Light Sources and Reflected Colour

In Colour Temperature, we looked at the levels that different parts of the light spectrum emitted by different light sources such as tungsten and daylight. These have an effect on the amount of colour that is reflected back at the eye or camera. How to control that was detailed in Colour Correction and colour temperature often seems to be the centre of a photographers universe.

The spectrum of light colour bounced back is down to colour of both light source and target. Sometime these are in harmony, sometimes not.

So, we have a 3 way equation. The spectrum emitted by the light source, the reflection from the target and the perception capabilities of the eye/camera.

What’s special about LEDs?

I don’t know much about making LED’s but for whatever reason, they can have a less “rounded” spectrum output than say a tungsten light source with a gel over it. This create “spikiness” in the spectrum graph. One particular blue wavelength is stronger that the other blues etc. Green LED’s often have a higher spectrum output altogether, compared to Red or Blue ones.

This can cause particular colours to appear to “zing” out or make sets and costumes unexpected shades of odd.
The addition of Amber LED’s (RGBA) goes some way to smoothing out the spectrums for some colour mixes and manufacturers are producing improved LEDs. LED packages have their own colour spectrum graph, the cheaper ones are the worst offenders. Something to bear in mind when your Cheapo PARSplats are creating colour havoc and driving the snappers mad.

While trying to find some easy to understand illustrations on this, ETC announced last week that they were welcoming LED guys Selador into the fold. Luckily for us, this article has some useful graphics.

What is the colour temperature of LED stage lights?

This is asked by photographers a lot. They are happy knowing that Tungsten is 3200 K and Daylight is 5700 K and have equipment set up to deal with this. Of course, the actual colour spectrum emitted by any lighting fixture is a variable set of wavelengths of different strengths. This is true of LED fixtures, including “White” LED’s. Even setting a white balance with one LED state, doesn’t help much the minute you crossfade to something else.

Manufacturers sometimes refer to the Colour Rendering Index (CRI), particularly with wider spectrum sources such as white LEDs. Though not without it’s own limitatons, the CRI could be thought of as an indicator of the amount of the spectrum a light source emits. A tungsten light source has a CRI of 100, while those horrible streets lamps that are no use for reading maps (Low Pressure Sodium) might have a CRI of less than 5. There is some basic information on CRI here.

So, the actual colour temperature of LED stage lights is not particularly relevant. Individual LED’s have a spiky spectrum graph and colour mixing with cheap LED PAR Cans can create all kinds of chromatic weirdness. Add to that that fact that a digital camera is not as high spec as the human eye ,you might feel a bit sorry for your photographer.

That’s before we even get to video cameras, PAL/NTSC and gamut.

LED’s, Dimming and Cameras

If stills photographers have to deal with the ghastly colours your rig is firing about all over the place, video cameras can go one better.

Dimming tungsten lighting, the electrical waveform is chopped rapidly and the filament cools down to a lower intensity level while remaining lit. The dimming in discharge lamped moving heads is provided by the physical cutting down of light output using a mechanical shutters.

Dimming LED’s using variable electrical currents is inefficient and isn’t good for the LED. For this reason, many LED lighting fixtures use techniques such as Pulse Width Modulation to control light output. This flashes the LED on and off at different speeds, creating a change in perceived brightness.

As videos cameras use the the rapid capturing of still images to produce moving pictures, the possiblity of a conflict between the different cycles can cause strobing on camera. Most sophisticated (and expensive) LED systems have improved dimming cycles but again cheap imported LED fixtures can be a bit rough. Some of them even strobe to the naked eye!. A short term solution is to adjust the levels of the LED fixtures until the strobing is not so noticable on screen.

Take Home Points

• Colours from light sources reflect from coloured surfaces.
• LEDs have spiky colour spectrums.
• Cheap LEDs are cheap for a reason.
• Photographers will always complain about your lighting.
• Don’t start a discussion about colour theory at 2 in the morning.

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

You May Also Like:

• Colour Temperature
• Colour Correction Filters – More Stage Lighting Gels
• Reflected Colour in Stage Lighting Design

As LED technology becomes cheap, using LED stage lights is a hot topic in the world of stage lighting. The possibilities of using a low power, high brightness LED light with colour mixing capabilities seems hard to resist but how do you control your LED lights? Stage lighting controllers vary widely in both cost and features so On Stage Lighting considers cheap led light control using your existing lighting desk.

Image by Tim Morgan

Are LED stage lights “intelligent”?

The term “intelligent” in stage lighting usually refers to the remote control of the lights using sophisticated systems to adjust different parameters in the fixture such as colour, gobo and effects. The intensities of the LED’s themselves are under the remote control of the lighting controller, as are any onboard effects such as strobing or colour chases that come from within the “brain” of the LED fixture itself. LED stage lights do not require the use of a normal lighting dimmer- they just need power and control signals.
So, LED stage lights fit into the “intelligent” lighting category.

Do I need a special LED lighting control?

Led stage lights are usually controlled using the DMX 512 protocol that is widespread in the entertainment industry. Any lighting controller that can output DMX will be able to control LED fixtures. The fixtures themselves have a “fixture personality” or DMX map, and this tell us which DMX channel is used for. Control channels could include: Red, Green, Blue, Amber, (some LED colour mixing fixtures have another colour, in addition to the RGB model), Effects etc.
So, you don’t need a “special” LED light control. You could use a conventional DMX lighting desk, even a manual one (a lighting control with no “scene” memory).

Like the desk I’ve already got at [insert venue here]?

Yes. Unlike more complex “intelligent” lighting kit, LED fixture personalities are fairly simple. They often use 6 DMX control channels and can be controlled on a little as 3 (1=red, 2=green, 3=blue). Using a simple lighting desk to control moving lights effectively is difficult, but controlling LED stage lights is easier and a conventional lighting desk can do it. A tiny lighting control with 6 faders could be used as an led lighting desk for 20 fixtures – provided they were all set to the same DMX start address and you don’t mind them working in sync.

Conventional stage lighting controllers mix their faders levels using Highest Takes Precendence (HTP) which is great when using colour mixing LED lights. Fade up “Blue” and add the “Red” channel and you get a genuine mix of those to colours (they give you a sort of magenta colour) that fades up and down with the control faders. Intelligent lighting controllers can use both HTP or Latest Takes Precedence (LTP) so check how the LED fixture channels are being mixed – I would choose HTP for most uses.

What is the best way to control LED stage lights?

The best way to control LED stage lighting depends on:

• The amount of flexibility you need. Does each unit need to be individually adjustable?
• The rest of your lighting rig. Have you got other fixtures to control such as moving lights?

If you have 96 dimmers, 20 LED battens, 10 LED PARs and 10 moving lights, you will want to use a dedicated moving light control. But, if you only need to change the colour of a few LED PARs , you don’t need a complex LED lighting controller. Make sure that you also look at what available in PC based DMX lighting control software.

Don’t forget – many LED stage lighting fixtures also have a number of programs built into them to allow colour control, static or chases, that can be used with no lighting controller at all. These are usually called “Stand Alone” mode and are great if you need to just set up your LED lights and go.

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

You May Also Like:

• DMX PC Lighting Software – Cheap Stage Light Controllers
• Led Moving Light Review – Studio Due NanoLED
• Lighting Desk Basics – Beginner’s Guide to a Stage Light Control – 1

The Studio Due NanoLED (.pdf) was shown as this years PLASA Show 2007 in London amongst a truckload of LED stage lighting fixtures that are coming on to the market. So what’s up with this tiny, manic waggly LED thing?

LED moving lights are a marriage of two stage lighting technologies popular at the moment, the moving light and RGB colour mixing using LED. Much stage lighting technology development at the moment seems to be a technical answer to a problem that may not have been asked yet! //end of cynical old LD mode.

On Stage Lighting recently got to put some of these units through their paces in the UK.

Technical Stuff

The NanoLED moving light has 14 3W LED’s arranged in array on the front of a unit with a cute moving yoke with pan and tilt control. The fixture has the 3pin DMX In and Out connectors and a menu screen and four buttons to control the settings, like many moving lights.

Out of interest, the maximum 12 DMX channels of control for this LED moving light are:

• Ch1 = Red – Intensity of the Red LEDs.
• Ch2 = Green
• Ch3 = Blue
• Ch4 = Strobe/Rainbow – Preset LED colour and strobe effects
• Ch5 = Pan Coarse – Control of sideways movement
• Ch5 = Pan Fine – Fine control of moving light Pan (many lighting controls have a feature to easily access fine control.
• Ch7 = Tilt Coarse – Up and Down movement of LED
• Ch8 = Tilt Fine
• Ch9 = Dimmer – An overall LED intensity master control. Some LED fixtures don’t have this feature meaning that, to lower the intensity of the whole fixture, you have to fade down each set of Red, Green and Blue LED’s – boring.
• Ch10 = Motor Speed – Control of the movement speed can be adjusted. Some basic moving light controls have poor or non-existent DMX fading capabilities that can overcome by setting the “Mspeed”.
• Ch11 = Fade Speed – Similar to Mspeed, this can be used to set the fade rate of the LED intensity.
• Ch12 = Reset – Reset Functions and other housekeeping.

In Use

The Studio Due NanoLED is neat, stylish and QUICK. Because it is so lightweight, the LED head can move quickly, although slow movement effects were best achieved using the Mspeed control, as DMX fades on the Pan/Tilt Coarse channels were a bit steppy/jerky.

The LED colours are good enough and mixed well on a surface a little way from the fixtures. The rainbows and strobes are useful if you don’t have a high end professional moving light controller or any time to program effects.

A problem I have with LED moving lights is that, because they use an array of LED’s, you don’t get to see a single colour point source. If you put an amber gel in a PAR can, when you look at the PAR can, you see Amber. With LED array moving lights you see a load of Red and Green LEDs. This spoils your looks when pointing your lights back towards the crowd.

The way to get a single colour light source from an LED array is to fit a highly diffused lens (not available for this moving light at the moment). But this stops any beam throw from the lights and is more useful for the “look” on television.

The brightness of LED’s in stage lighting, and now LED moving lights, is a question in the industry at the moment. Yes, they are fantastic, efficient and a great leap forward. But don’t expect this little moving LED to blow away your small PARs in the brightness stakes. Why Buy LED Stage Lights looks at some of the pitfalls of using LED fixtures.

Because this LED moving light is so small, it is best used in bulk. Two fixtures in your DJ rig will add a couple of colour changing beams to your truss (but not the cheapes way of doing it), but 20 of these units in a light curtain with smoke or haze better.

I can see a high tech replacement for the 9way PAR36 Areo (or ACL – AirCraft Lights) behind the drum riser.

Cue smoke!!!

More at LED Stage Lighting

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

You May Also Like:

• LED Light Control – DMX Controllers for LED Stage Lighting
• Moving Light Control – Groups – Lighting Desk Basics 3
• Moving Light Control – Palettes – Lighting Desk Basics 4

LED lighting for stage and theatrical use has never been so cheap to buy. It seem like every major stage lighting manufacturer has dived into the LED lighting fixture market while cheap imported lights mean that even a small band or DJ can get a slice of the RGB colour mixing action. On Stage Lighting has a guide for anyone thinking of buying and hoping to learn more about LED stage lighting fixtures.

Why Buy LED Stage Lights?

High Powered LED (Light Emitting Diode) technology means that we can now use those funny little glowing things that used to live on the front of your television, in theatre shows, live music gigs and corporate shows. LED fixtures have many advantages over “old fashioned” lanterns that make them attractive in stage lighting.

• Low Power Consumption – Because the LED uses a fraction of the power of an normal lightbulb (lamp), the power consumption of LED lighting fixtures is very small, meaning you can use a lot of fixtures on small power supply such as a 13A domestic socket. This is great for small band lighting rigs and the disco/party DJ.
• Low Heat Radiation – Although LED stage lighting does produce heat, the fixtures produce light without getting extremely hot. Modern stage lighting lamps produce more heat (and light) than they ever have and this has been coupled with improved lantern casings to minimise the risk of burning the operator. There are, however, some environments where the low heat properties of LED stage lighting are desirable.
• Lightweight and Portable – The hardware that LED fixtures are packaged in does not need to be heavy and, although the various power supplies and elements all add weight, LED units are usually fairly light.
• Colour Effects – The most common way for LED lights to be used for stage lighting purposes is using a combination of different coloured LEDs. A fixture with all three three lighting primary colours, Red, Green and Blue (RGB) LEDs blended together in different combinations gives the lighting designer loads of colour choices. This is using a principle called Additive Colour Mixing, where the coloured LEDs mix on any surface that reflects the light.
• Small and Compact – LED lighting fixtures can be made in small, discreet packages which suit applications where size and brightness are important such as exhibitions stands.
• High Brightness – This really comes down to the ratio of light brightness to power consumption. The new high powered LEDs are very bright considering small amount of electrical power they use.

So, What Types of LED Lighting Fixture Might I Choose?

For the purposes of stage lighting, the RGB colour mixing (see above) capabilities of the LED fixtue is it’s selling point. The main forms are in a lighting batten, a long strip with an array of red, green and blue LEDs or in a compact array that produces a beam of light, similar to a conventional PAR can or a Floodlight. The batten are useful for lighting up flat areas, such as a wall or backcloth, while the PAR / Flood fixtures will give you a beam of light, similar to their conventional stage lighting relatives.

Moving Light technology has also joined the LED bandwagon, with LED arrays being packaged in all shapes and sizes of “waggly” LED Moving Head fixtures. Another stage and theatrical use for the LED is in a large, screen-like array which can be used to show colours, patterns and moving images like a low resolution television screen.

How Do I Control My LED Stage Lighting?

Stage lighting is usually controlled using the standard DMX512 protocol, and LED fixtures are no exception. Different DMX channels control the Red, Green, Blue while other channels may deal with overall instensity or special chases and effects. The LED lights are linked to the DMX signal chain in the same way as other intelligent stage lighting fixtures and do not require extra dimmers to control them.

If you don’t have a DMX lighting controller, many LED stage lighting units can be used in “standalone” mode or can have control locally, using a simple controller/power supply that enable you to change the colour and run simple effects.

What’s the catch about LED stage lights , then?

LED stage lighting is cheaper than ever, uses less power, is smaller and doesn’t get hot. It also offers you a range of light colours, without using lighting gels. What more do you want?

Well, there is a few things you might want to know about LED stage lighting, before you go out and buy a van full.

• LED arrays can’t “focus up” like a conventional lantern. Because there are many sources of light in the fixture, you can’t get a sharp spotlight or project a gobo using an LED fixture.
• The “endless” colour choices have limits. Different LED stage lights have various colours that they just “don’t do”. A good quality white light is one of them. Because of the way that all three colours (RGB) are mixed, a good even white light is near impossible to achieve with most fixtures.
• LED lighting fixtures are bright – but not that bright. Although power for instensity-wise LED stage lighting fixtures are really efficient, they do lack the punch of their conventional lantern relatives (for the moment). A PAR can with LEDs in it is nowhere near as punchy as a PAR64 CP62 (or even a PAR56, for that matter).
• Intensity drops off quicker over distance. Or at least , it appears to. Because most LED lighting units have neither a lens nor a reflector, the light they produce scatters and struggles to maintain intensity when thrown much of a distance.
• Colour mixes better over distance(?). Because the three coloured LEDs need to mix on a surface to create an even light, this mix improves further away from the light source. This produces the dichotomy of a fixture that colours mixes well when it is too far way to mantain a good intensity.
• You get what you pay for. All LED stage lighting fixtures are not the same. Even though you can buy them cheap doesn’t mean that you should and all of the above points are more apparent in cheap LED lighting fixtures. A good quality lighting manufacturer will always be more expensive but, in general, the quality of the light and fixture will be far superior.

While having their faults and limitations, DMX controlled LED lighting fixtures are an important development in the techonology of stage and theatre lighting. They expand the armoury of the lighting designer and will help save the planet – a bit. If you have any thoughts on LED stage lighting or have a question to put to On Stage Lighting, please use our comments box below.

Click here to see a range of LED PAR fixtures and LED Battens

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

You May Also Like:

• What Stage Lighting Should I Buy? Intelligent Or Conventional Lights?
• LED Light Control – DMX Controllers for LED Stage Lighting
• Led Moving Light Review – Studio Due NanoLED