LED Stage Lighting

A rock concert yesterday made me ponder on some of the differences between the old and the new ways of lighting a stage.

For some inexplicable reason, modern stage lighting seems not so much focused on illuminating the actual performers as on flashing harmfully bright and narrow coloured beams or flashes into the eyes of the unsuspecting audience at irregular intervals during the concert. How this practice can be even legal is probably a matter of ignorance on the part of lighting technicians and regulating authorities. Sometimes real laser beams are used.

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The new LED technology has both advantages and disadvantages.

+ LED uses less energy (if power factor is good) and lasts much longer (if drivers are of good quality and don’t get overheated).

+ LED floodlight does not emit heat in the beam direction as incandescent light does, so performers will not overheated from the lighting.

+ LED diodes are small and versatile and can be used for more creative effects if so desired (as exemplified at the London Olympics).

+ LED diodes are already coloured and directional and do not require coloured filters.

– LED light is much sharper and more laser-like than incandescent light. It’s a sort of digital light that is either on or off, with no softly glowing tungsten filament to ease the transition. It thereby lacks some of the charm of older types of stage lighting and gives a more high-tech effect that is less flattering to performers and much harder on the eyes.

– Cool white light it is horridly harsh, unflattering and a real mood-killer, compared to the warm sunny glow of traditional tungsten light.

– Blue, green and cool-white LED light can damage the retina if bright and beamed directly into the eyes.

My recommendation to stage lighting technicians:

• Rethink the practice of lighting up the audience at all. People come to watch the show, not to be illuminated themselves. Therefore lighting should be directed towards the stage, not be placed at the stage and directed at the audience. If lighting effects on or around the stage are desired, they should be only be decorative (e.g. non-directional, low-lumen dots or panes) and not illuminating.

• Avoid cool white light. Complement the coloured LEDs with halogen floodlights if you want performers to look good on stage. Just a few won’t add that much heat.

• Use blue light sparingly and don’t direct it into people’s eyes.

• Don’t use lasers. If you have to, don’t direct them at any living being.

• Don’t use strobe lights as this can cause epilepsy in susceptible people and is generally irritating.

For the audience I recommend bringing sunglasses as well as ear plugs in order to avoid eye damage until lighting designers have learned how the new technology can be used safely.

Good article about stage lighting with LED:

LED Stage Lighting – Why Buy RGB LED Stage Lights?

 

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Lamp Guide

Now that the market is being flooded with such a confusing profusion of different lamps to replace the incandescent bulb, it is more difficult than ever to find the right lamp for the right place.

Swedish national TV consumer program Plus last week tried to sort it out with the help of Kalle Hashmi at the Swedish Energy Agency, STEM. [1] My translation of his unusually informed and balanced recommendations:

• In closed luminaires it is not advisable to use CFLs as they get too hot which shortens their life. Where you have very short burning time, such as in a closet or the bathroom, the lamp life will shorten significantly if you turn it on and off a lot. In such a situation you could preferably choose a halogen lamp.

• If temperatures are too low [= outdoors in northern winters] the [CFL] lamp does not perform at its best. The lamp is made to function best in 25 degrees [C]. In such a situation we think the best option is to use an induction lamp. Very expensive but on the other hand it lasts 100 000 hours.

• When you get older, 60+, you need more light to be able to see, and our ability to distinguish colours and contrasts diminishes. Then we need to choose a light that solves all three problems.

• When it comes to contrast, for example, it is usually limited to reading text, black on white. Then you need to choose a CFL with higher effect, e.g. 15W and you can use a correlated colour temperature around 4000K, but only for reading.

• When in a situation where colour rendition is very important, where you need to match colours, then it is very important to use a mains voltage halogen lamp because it has much better colour rendering capacity. It can be a situation like cooking, where all colours seem matte to the eyes. So what an elderly person perceives as ‘brown’ may actually be burnt. With halogen you see better.

• CFLs are not the answer to all our prayers. When it comes to colour rendering they are not as good, and they also contain mercury. LEDs will be the dominating technique, but it’s better to replace low voltage spotlights with LED spotlights than replacing standard bulbs for general lighting.

My comments: Good advice all of it, except for the recommendation to use cool-white CFL for reading.

Some research suggests that contrast decreases rather than increases with higher correlated colour temperature (blueness) and that certain blue wavelengths may harm rather than help in cases of macular degeneration. [2] The small traces of UV which some naked CFL tubes emit may at close range may also worsen cataracts and skin conditions. [3] If you sit closer than 30 cm for more than an hour per day, the the British Health Procection Agency recommend that you use a covered CFL with an extra outer bulb. [4] 

I would instead recommend frosted incandescent or halogen for reading, as clear bulbs tend to give disturbing light patterns on the page and most LEDs are either too dim or too directional. Unfortunately, thanks to the European Commission, that’s no longer an option.

Replacing spotlights with LED is a better idea as LEDs are already directional by nature and perform better as reflector lights than as omnidirectional light trapped in a bulb – if you don’t mind the slightly lower light quality and paler colours which can be seen clearly in this comparison between ‘warm-white’ & ‘daylight’ LED and incandescent downlights:

More tips:

For those who prefer a daylight-simulating light, despite the lower contrast, white LEDs are naturally cool-white already and need no special phosphor mix like CFLs to achieve a daylight look.

But daylight lamps usually look best in the daytime. At night the cold light can look and feel more unnatural when contrasted against the dark as we humans are traditionally used to firelight at night (though cultural and individual preferences may vary).

• Where warm-white incandescent type light with perfect colour rendering is needed, there exists no replacement other than halogen (which is also incandescent). No CFL or LED has that special sunny feel and warm glow which makes colours come alive. 

 In traditional environments with antique furniture and art, CFLs and LEDs tend to look particularly out of place, whereas they may look acceptable with more contemporary designs, even if a bit dull. 

• When it comes to mood lighting of your dinner table, cosy corner or favorite restaurant, CFL and LED have zero romance factor whereas the warm light of halogen or incandescent spots on dimmers will complement candle light and create an attractive, romantic and relaxing atmosphere.

In rooms where you’re mostly sitting down and relaxing (like the living room), use many low-watt (7, 15 or 25 watt if incandescent) lamps placed low around the room, e.g. on walls, tables or in windows, rather than one bright ceiling light. Can be complemented with floor reading lamps and ceiling floodlights to be turned on when needed. Avoid up-lighters and torchieres.

• Around children, I’d use only warm-white LED lamps (which are cool to the touch) or low watt frosted incandescent bulsb in enclosed & shaded luminaires. CFLs contain mercury and can break and should therefore never be used around children or pets. Clear halogen lamps can get too hot, bright and glaring. One exception is IKEAs Snöig series of desk, walland floor luminaires where the halogen lamp is well protected from curious fingers and eyes.

• For night-lights, I recommend LED. Even if you only save 6 watts per lamp, they’re usually on all night, every night, and come in different colours. 

• Coloured lights, e.g. holiday lights, car and traffic signal lights, stage lighting etc. can be replaced by LED. LEDs come already coloured in various colours and are often ideal due to their smallness, low energy use and lack of excess heat. Paying for premium quality incandescent light, only to filter out most of through a colored glass, is truly a waste! 

Detailed home lighting and lightbulb guide:
The Lamp Guide

More lamp comparison photos:
Snarkish Forum
Newest Lightbulb Tech Combines Advantages of Incandescent, Fluorescent, and LED
LED Tints

TreeHugger CFL guide:
Be Careful When You Shop For Compact Fluorescents

EU Commission’s interactive & multilingual Bulb Selector

Lighting design tools:
GE Lighting Style
Philips Lighting Design tool

References:
1. Plus, SVT, 17 sep 2009 http://svtplay.se/t/102796/plus
2. Artificial Lighting and the Blue Light Hazard
3. SCENIHR: Light Sensitivity
4. HPA – Emissions from compact fluorescent lights