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Comment by sp332 | Hacker News Reader

The low color quality, specifically the very warm hue, is a feature for nighttime lighting. Blue light messes with sleep cycles of humans and animals.

The very narrow spectrum benefits astronomers because it's easy to filter out light pollution from low-pressure sodium lamps.

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Just wanted to point out that the choice municipalities have made for street lighting is not really an LED technology limitation as much as different evaluation criteria.

For example, while sure, OSRAM advertises/sells street lighting LEDs that are broad spectrum (131 lm/W) [1] they also sell single-color LEDs like these amber ones that are actually even more efficient (141 lm/W) with an emission range almost entirely within 600-640nm [2].

This is almost as tight a range as LPS (which looks like about 580-610nm) [3], and it beats out HPS considerably [4].

[1] https://www.mouser.com/new/osram/osram-street-lighting-solut...

[2] https://www.osram.com/os/ecat/OSLON%C2%AE%20SSL%20150%20GA%2...

[3] http://www.flagstaffdarkskies.org/low-pressure-sodium-lighti...

[4] https://en.wikipedia.org/wiki/Sodium-vapor_lamp#/media/File:...

This was a big deal in Tucson for a while. It used to be that there was a city ordinance that mandated public outdoor lighting was all sodium lamps because it was super easy for the local observatory to filter out that one frequency of light.

Warm white LEDs exist, with color quality exceeding that of sodium vapor in every way, but cities often use blueish LEDs because they're cheaper and more efficient.

Relevant Technology Connections video: https://www.youtube.com/watch?v=wIC-iGDTU40

Warm white LEDs put out a broad spectrum. That's a feature for most illumination use cases, but it's hard to filter out of a telescope.

As a person who has spent a decade as an amateur student of human color vision, let me state emphatically that “color quality” is a horrifically bad criterion for choosing nighttime street lamps. Nobody should be trying to read a book or critically evaluate photographs in the middle of the road at 3AM.

Street lamps should include as little short wavelength light as possible and should otherwise be as even (this means: use more lamps spaced closer and placed at lower height, diffused and shielded from the side) and dim as possible, so as to avoid causing distracting glare in people’s peripheral vision, and avoid causing high contrast between areas directly under the lamps and areas in shadow. Human vision is amazingly good at adapting to very low light levels. After adaptation, humans can navigate the environment by e.g. starlight, but at any rate can see just fine under sodium lamps.

But the way cities roll out LED street lighting is to put a small number of widely spaced very intense blue lamps high up in the air, not diffused and with little shielding from the side.

Every parameter has been optimized (pessimized?) for blasting away people’s night vision and causing enough glare to make seeing into the shadows all but impossible.

Extremely low color temperature LEDs would be fine, but don’t really have any especially great advantage over sodium lamps. (Except maybe for getting some government subsidy money?)

I thought the wider spectrum of light coming from LED streetlamps means they can be run at a lower brightness to provide the same visibility, which means less overall light pollution (less reflection back upwards) and less power usage.

The little wild creatures don't appreciate that visibility. If the recent report on biodiversity loss bothered you, avoiding LED outdoor lighting is one easy action to take locally.

There's not a lot of biodiversity on the streets anyways, so that's not a big deal. but the little wild creatures do appreciate less light in the woods, which is what you get from less light pollution.

The light polution glow from cities can be seen from about 100 miles or so, so it's not a localized problem.

How does this compare to a full moon?

I assume animals have evolved to deal with that.

Not all month long. They've found that frogs won't sing if it's too light, making it hard to woo a reproductive partner.

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