“The beam spread of a floodlight is defined as the angle, measured in degrees, between points on a candlepower distribution curve which are 10% of the average maximum candlepower.” The beams are defined by the National Electrical Association in the chart below.
For floodlights that are not a circular pattern: The NEMA numbers may indicate the “H” horizontal width and the “V” vertical width of the beam. Example: 5H x 1V – Type 5 Horizontal and Type 1 Vertical indicates that the beam is horizontally wide [between 70° and 100°] and vertically narrow [ between 10° and 18°].
NOTE: MagniFlood DOES NOT recommend the 10% of maximum beam theory for quality engineered layouts, rather 50% of maximum beam should be used. Uniformity gives the best lighting results, although intensity should also be a consideration [10% of maximum beam candlepower is a percentage recommended by the Illuminating Engineering Society.]
The diagrams below are the angular ranges that define the five basic roadway distributions that are used for roadway lighting. They represent the area of distribution of a half maximum candlepower They represent the area of distribution of a half maximum candlepower isocandela trace within the longitudinal range in which the point of maximum candlepower falls.
Preferred width 15°, Acceptable range 10° to less than 30°
Preferred width 25°, Acceptable range 20° to less than 30°
Preferred width 40°, Acceptable range 30° to less than 50°
Preferred width 60°, Acceptable range 50° or wider.
Distribution is 360° which is symmetrical around the luminaire.