The quarterback fades into the backfield and heaves the football at a receiver near the end zone. Is it a touchdown? Fans don't know for sure, because they can't see the poorly lighted fringes of the playing field.

A badly illuminated sports field can be frustrating not only for student athletes who have to compete on it, but also for administrators trying to balance the need for better lighting with all the other facility demands placed on a school or university.

Older sports facilities typically used inefficient incandescent lighting. But improvements in lighting fixtures and lamps have made it easier for schools to upgrade athletic facilities with lighting that provides more illumination for less money.

Making the switch Metal halide lamps are generally considered the best choice for sports fields, says Gonzalo Aguilar, an electrical engineer in El Paso, Texas, who has designed lighting systems for several sports fields in the Ysleta Independent School District. Aguilar recommended metal halides for Ysleta's football fields, which were plagued by inadequate and inconsistent lighting.

Metal halides, a form of high intensity discharge (HID) lighting, emit five times the amount of light produced by incandescent lamps without giving off the intense heat associated with incandescents. They also produce color rendition that is superior to other HID lighting, such as high-pressure sodium vapor lamps, which deliver a "peachy" color.

A 1,500-watt metal halide lamp provides the best balance of upfront costs and efficiency, says Aguilar.

Having enough lighting is crucial for schools who want to televise their games. Aguilar says many older fields are illuminated at 30 footcandles. He typically recommends levels of 70 footcandles in his designs.

Besides increasing light levels, an effective sports lighting upgrade should try to achieve as much uniformity as possible-no dark spots.

Uniformity is measured as a ratio of the brightest part of the field to the darkest part.

"You want to get that number as low as possible," says Aguilar.

Lighting design can help achieve greater uniformity by aiming the lamps correctly and distributing the light in different patterns-a combination of wide and narrow beams.

Computer programs help lighting designers determine the precise horizontal and vertical angles of all the lamps that will deliver the most uniform and efficient lighting.