A call to improve London's lighting at night

Re:A call to improve London's lighting at night by quickthrowman on Thursday March 18, 2021 @01:05PM (#26504863)

LED lights do in fact have the ability to do different color temps, some fixtures have tunable color temp as well. In my home, I use lamps that output 2200-2700K depending on the dimmer setting. Lower color temps output less lumens per watt, and the goal of exterior lighting is generally to improve visibility, hence the 4K color temp.

Here’s a cutsheet for a Lithonia wall pack fixture showing the different options, there’s also a chart showing what the lumens per watt is based on the color temp: https://img.acuitybrands.com/public-assets/catalog/1008038/w...

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Re:A call to improve London's lighting at night by MayeulC on Thursday March 18, 2021 @02:28PM (#26505848)

The color a LED emits is given by the choice of materials (specifically, the band-gap, with E=hν, ν being light frequency https://en.wikipedia.org/wiki/Band_gap#Light_emitting_diodes... )

"Tunable" LEDs are just multiple LEDs, the goal being to change the emission peak. Peak wavelength can be mapped onto a black body temperature trough Wien's law (λpeak =2.8e-3/T) https://en.wikipedia.org/wiki/Wien%27s_displacement_law

I don't really know how the mapping is done, though, as there are different ways to map it since the LEDs won't have the same emission curve as a black body.

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