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Lights--by their very nature and makeup--deteriorate over time. It is a proven fact that poorly maintained lamps lose at least 10 percent light output per year. Factors such as weather, surrounding temperature and use and maintenance all play a role in the rate at which a lamp ages. Consequently, lamps lose the ability to give off the same amount of light they gave the previous day. To increase the life expectancy of lights and avoid an accumulation of dead spots on courts, several maintenance protocols should be followed.
Defining A Foot-Candle
A foot-candle is a unit of illumination used to measure the light output in candela per square foot, according to Tennis Courts: A Construction and Maintenance Manual, written by the United States Tennis Association (USTA) and the American Sports Builders Association (ASBA). This unit of measurement is still used at many recreational sites to evaluate the light output of court lamps. Terms and other units of measurement--such as lux, lumen, candlepower and radiance--all help build the discussion on defining a light source, but the usual measurement is foot-candles. (While I could digress here for a moment and attempt to sort out some of the debate on the measurement of light, I will leave that discussion for another day.)
The USTA and the ASBA have recommended average levels of foot-candles for tennis courts. Recommendations are based on the type of play on the court: