The lights are on in the afternoon to keep the light levels high enough for the broadcast cameras. If there are clouds, or the sun starts to set, the light levels could dip causing problems for the cameras and the viewers at home.
Requirements for stadium lights
1）The safety performance of lamps and accessories should comply with the relevant standards.
2）The lighting protection level of stadium lights and lanterns is in line with I lamps or II lamps with metal casing grounding.
3）Luminaire efficiency: high-intensity gas discharge lamp not less than 65%, grille fluorescent lamp not less than 60%, transparent protective cover fluorescent lamp not less than 65%
4）The lighting of lamps and lanterns should be compatible with the installation height, location and lighting requirements of stadium led lighting. Light beam and medium beam lamps should be selected for an outdoor stadium, and medium light beams and wide beam stadium lights should be selected for the indoor gymnasium.
5）Lamps and lanterns should have anti-glare measures, and stadium lights and accessories should meet the environmental requirements. Lamps and lanterns shall be of high strength, corrosion resistance, and electrical accessories to meet the requirements of heat resistance.
6）Lamps installed at high altitude should be selected with light weight, small volume and small wind load coefficient.
7）Fall prevention measures for stadium lights