Two factors have an impact to sky glow or light pollution, which are up-light and the lumen output (light level) of the fixture.
To address the up light, the majority of the new LEDs are “cobra-head” fixtures and they have received the best ranking – a “zero” – when it comes to the amount of up-light they produce. FortisAlberta’s fixtures are “Dark Sky” friendly with zero up-light, which means less light pollution and/or sky glow as the light is directed downward.
To address the lumen output, LEDs typically require approximately 47-58 per cent of the lumen output of the HPS light to achieve the same light levels on the pavement. This is due to the efficiency of the light source being able to direct the light where it needs to be versus the HPS light having a lot of wasted light and lack of control.
By eliminating the up light and reducing the lumen output of the light source, the LED significantly reduces light pollution.