Lighting lingo guide
Architectural lighting
Architectural lighting design is a relatively new field that combines architecture and engineering. It was recognized as a legitimate profession with the formation of the International Association of Lighting Designers in 1969. Its goal is to define spaces through artificial sources of light. Although lighting design is now part of certain architecture curriculum at universities, many lighting designers, like Gilles Arpin, emerged out of theatrical lighting.
Colour temperature
Colour temperature describes the temperature of white light, and is often measured in kelvin (K). Lower colour temperatures like 2,700 K or 3,000 K are considered warmer and have a golden tone. Higher colour temperatures that range between 3,500 K and, in the case of the Notre-Dame Basilica, 6,500 K are cooler and appear more bluish.
Optics
One advantage of LED luminaires is their excellent ability to deliver light where you need it, and only in that direction. Because other light sources are spherical, they emit light in all directions, and require a reflector around the bulb to capture the rays. This is where about 40 per cent to 50 per cent of the energy in traditional light sources is lost. LEDs can be configured with tight or large optics, or beam angles, that can be pointed toward a specific area on a building façade. Optics for round projectors like the Lumenbeam can be as narrow as six degrees or as wide as 80 degrees. For example, the three statues above the basilica’s entrance are lit using narrow sixdegree spots. To backlight parts of the towers, however, larger 40-degree angles are used to cover more area. For linear projectors like the Lumenfacade, another range of optics is available since beam angles are asymmetrical, coming from both the length and width of the fixture. On the Notre-Dame Basilica, slim optics of 10 degrees (length) by 60 degrees (width) are used to graze the surface. But to evenly envelop the church entrance in blue light, wider optics of 30 degrees by 60 degrees are used.