Feature Article - October 2004
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Let There Be Lighting

How to illuminate the world inside and outside your facility

By Kyle Ryan


EXODUS

Even or uneven, Schaumburg's Olympic Park had no lighting system in place. A relatively new construction, the park was built in phases as funding became available. Light controls are being housed in a concession stand that's under construction.

"We decided that we have such a demand for a lighted athletic fields that by utilizing the lights, we'd get some extra time," Otto says. "Basically what you end up doing when you have a big tournament, your last game is over by 8 o'clock. We can extended those hours to 11…That gives us three additional hours per field if you're in a tournament. That's three additional games per field, so that's pretty substantial."

Otto says light levels on the softball fields tend to be around 50 fc in the infield and 30 in the outfield, which is about a recreational level. Because the soccer is different (bigger ball, eyes more focused on the ground), Otto says they keep light levels on the soccer fields to about 30 fc.

The more light needed for outdoor areas, the more issues come up with light pollution, especially when there are nearby residential areas.

Pollution generally comes in three forms: sky glow, trespass and glare. Sky glow happens when light aimed upward (or reflected off the field surface) creates a low-level glow. Any resident of a major city knows the result: few visible stars.

Whitman has encountered readings on field surfaces showing that as much as 10 percent of the light gets reflected off the field. With sports (especially baseball or softball), a certain amount of sky glow is necessary so players can track balls in the air. Otherwise the balls disappear in the dark and become visible only a second before impact. Sky glow can be controlled by special visors that restrict light traveling above the fixture.

Light spill occurs when light travels into areas outside the boundaries of the field.

Schaumburg's strict lighting regulations dictate no more than one foot candle's worth of light can strike a park's property line. Luckily for Olympic Park, its 72 acres aren't near a residential area, but Otto and company remained cautious and purchased fixtures with special shields to eliminate spill. The shields restrain the light beams to certain areas and can be set to contain light within specified space.

While Whitman describes light spill as easily calculated and reduced, he admits that glare isn't as easily subdued. Glare is light that's in sharp contrast to the area surrounding it.

Glare and light spill aren't even measured the same way. Spill light is measured by illuminance, light falling on a surface. Glare is measured by the intensity of the luminance, that is, the concentration of light in a certain area.

"Typically residents object mostly to glare issues," Whitman says. "But the bad thing is since people are all different, different people are affected in various manners by the same amount of glare…There's not a really easy way to measure glare, what actually bothers people. It's a very subjective thing."

Glare isn't invincible, though. Whitman's firm set a glare standard that proved so effective the city of Seattle adopted it: The luminous intensity of a fixture is calculated, then engineers limit it through mathematical calculations.

"Most people don't do these kinds of calculations when they do a sports field, and that's why there are so many terrible sports fields," Whitman says. Those are the kinds of fields people remember, and those memories spark opposition to park lighting.

"Typically a big problem with sports fields is the amount of glare coming from the field is not limited, and people can see it for miles around," Whitman says. "Properly designed fields, they're very unobtrusive. It's not that they don't have some glare impact, but they're very unobtrusive."

One of the "obtrusive" aspects of outdoor recreational sports facilities are light poles. Standing above the trees, they are gawky necessities. Nearby residents, when they grudgingly allow lights to be installed often insist the poles be short so not to harm the area's aesthetics.

Such a setup creates greater light-control issues, according to Whitman and the International Dark-Sky Association, a advocacy group that monitors light-pollution issues. Lower mounting heights require a higher angle for aiming the lights, which sends more light off-site. Taller poles for mounting lights reduce the angle of the light's aim, keeping the beam focused on the ground.

"That's a little bit counterintuitive because most people are familiar with, in terms of area lighting, parking lots and streets," Whitman says, adding such lights become less obtrusive as you lower them. The beams go straight down, and as the lights get closer to the ground, there's less spill light. So why can't sports fields be the same way?