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Energy-efficient lighting

Compact fluorescent and LED lighting can reduce both studio heat and required power in broadcast facilities. June 1, 2009

One thing about television: It is first and foremost an analog medium, even in its digital representation.

Now that I have your attention, or ire, let me explain. Television begins and ends with light. Lenses gather photons and focus them on sensors, which is undeniably an analog process (quantum mechanics aside). Even when computer graphics create the images, simulated lighting is used to get the human eye and brain to equate the CGI to the effects of light on real scenes. Images are thus captures. These are then transmitted and finally displayed, again turning electrons back into photons. This results in analog light that we perceive. Our perception might be time- and place-shifted from the analog experience, but it is nonetheless the purpose of television to replicate an analog perception of a scene. Indeed, one German word for television, Fernsehapparat, literally translated is “farseeing apparatus.”

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Without lighting, we would not be able to make images. Therefore, it seems logical to conclude that lighting for television (and film) is best done when it is not noticed — when it is replacing natural light in natural scenes so as to make the brain think that the images are constructed in the real world.

Energy-efficient fixtures have multiple benefits

Next to high-power transmitters, light has historically been the most voracious user of energy in a TV operation, not considering the time diversity usage patterns for a studio. In the early days of color television, the rule of thumb was that studios consumed between 50W and 100W per square foot of production space. In a 60ft × 80ft production studio, that amounts to more than 400,000W on the high end. Today, the NAB Engineering Handbook still recommends 55W, in any event a consequential amount of power to which one must add the power that HVAC systems contribute. Development of advanced camera sensors has contributed to a huge improvement in sensitivity, which allows lower light levels. Modern cameras list sensitivity 10dB better than a decade ago, and the transmission through lenses is better due to improved materials and much larger elements.

Lighting system technology took a large step toward improved energy efficiency when compact fluorescent studio lighting was introduced in 1981. Traditional incandescent lighting consumes up to 90 percent more power for equivalent light output. Heat generated is proportionally lower as well. There is no free lunch, of course. Dimming fluorescents requires special dimmers and, unlike point source lights like Fresnels and other focusable fixtures, they offer different artistic results. You would be hard pressed to light a TV drama with fluorescents, but a TV news set can be illuminated by mostly, or all, low-energy fixtures. Lighting with alternatives to incandescent fixtures is different enough that planning an installation and executing a lighting plan should be done by someone with experience.

The bulbs used in fluorescent fixtures are not the same as you would find in a hardware store. They are available for 3200? K applications as well as 5000? K. A second benefit is the exceptionally long life of at least 8000 hours. The net effect is a huge economic advantage in operating cost when all factors are considered.

LED — the path from consumer to broadcast?

Over the past year, there has been a lot of press about LED lighting for consumer applications. I have installed some myself with good results, albeit in a kitchen, not a studio. Automobile LED headlights and broadcast tower LED lights have become available recently. Their expected life greatly exceeds fluorescent, at 50,000 to 100,000 hours in some applications. Like fluorescent, they are not a point source at high power. Thus, for studio applications, they are more likely to show up in area lighting, cyclorama lighting and soft lights first. Several companies are now distributing fixtures with an array of high-power LEDs. They are very energy-efficient, and some are dimmable. A 50W LED luminary is reputed to put out the same light as a 650W Fresnel, though not the same pattern of illumination.

It is important to consider more than just the light level and operating efficiency, particularly with a new technology. When compact fluorescent technology first was used in television, many were skeptical that colorimetry and the throw patterns available would work for broadcast use. Experience has proved that it is a workable technology. LEDs need to be evaluated by the same inexorable approach. They inherently are not wide spectrum devices, but some manufacturers have developed proprietary packages, which include phosphor coatings on the package that provide better spectral response and more even illumination. LED lighting has penetrated photographic studio applications recently, and it is now starting to show up in broadcast fixtures.

At this time, LEDs have one serious trade-off that must be evaluated. Though they last an incredibly long time, they are very expensive. It is reasonable to expect that over time, as production volumes ramp up, the cost will come down. In no small measure this is because manufacturers are betting on consumer applications driving volume production rapidly upward. Like other pieces of the television puzzle, such as the camera, we benefit when huge amounts of research goes into consumer products that can be repurposed directly or leveraged into broadcast products.

Dimming 101

Lastly, controlling studio lighting with dimmers is a virtual requirement for effective creative control. For incandescent fixtures, dimmer sizes and types are highly evolved, and systems are quite standardized. Using newer high efficiency technologies renders large dimmers, in the multiple kilowatt range, rather redundant, or at least gross overkill. Dimmers appropriate for LED and compact fluorescent luminaries are available, and their capacity is appropriately a fraction of what we are used to dealing with.

Lower long-term cost, less environmental impact, with acceptable compromises is not a bad place to go in our energy-conscious economy.

John Luff is a broadcast technology consultant.

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