LED Light Pollution: Can We Save Energy and Save the Night? (2015) | Hacker News Reader

LED Light Pollution: Can We Save Energy and Save the Night? (2015)

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50 pointsrfreytag45 comments

They replaced the old lighting with white LEDs on my block a couple months ago.

First off, it actually makes it MORE difficult to see (now that the trees have leaves) than the orange light did. The LEDs are so much brighter that the contrast makes the shadows even deeper than they used to be, and your eyes can't see anything that's in shadow.

Secondly, it makes it much more difficult to sleep. My windows are ABOVE the lights (which face downwards), and it's like trying to sleep in daylight. I can't imagine what it's like on the floors below. My sleep has definitely suffered.

Why are streetlights shining up anyways? I see these curved glass installations everywhere. The light shines way above street level. At a minimum, this seems like a waste of energy, let alone the annoyance. In residential areas particularly, they should be very tightly constrained. And output adjusted to aid in night vision, not attempting to provide full lighting.

I couldn't agree more that more attention should be paid to where the lights shine and how they affect night vision, but they don't even have to direct any light upwards to make It bright enough to affect sleep on the floors above.

Even with all the light emitted downwards, a narrow street with bright and closely spaced streetlights means that there's enough reflection off pavement, cars, building facades and windows, etc. that a huge amount of light is reflected back above the lamp.

Depending on where you and the trees are relative to the lamp, the leaves may lessen or exacerbate the effect. And overcast nights make it even worse because you get a second dose of reflection (from the entire metro area, much of which has been similarly "upgraded" to Hollywood interrogation spotlights... I mean, LED streetlights.)

It's not as if anyone was claiming this neighborhood was dangerous or scary to walk in at night. If I wanted to live in Times Square I'd live in Times Square.

I also noticed the shadow problem. And with some fixtures, the shadow itself can have a strange pixelated look - https://i.imgur.com/e0nReZ8.jpg

At the same time, the city looks much more beautiful to me under LED lighting.

Wow, that's an unpleasant effect!

Higher kelvin lights look so much better in my opinion. http://i.imgur.com/XHqUPOY.jpg

That also has a lot to do with the whole emission spectrum, not just where it falls on the black body curve.

Low pressure sodium, for example, is a very narrow wavelength spike [1]. If you look at your hands under this, they appear as a kind of nasty gray with veins sticking out. Awful color rendering. [2]

On the flip side, it doesn't scatter as strongly in the atmosphere, and the narrow wavelength band is much easier to filter out of measurements. So there's a tradeoff. If you don't care about dark skies, then phosphor-converted blue LEDs look like a pretty great idea. If you do, then make an informed decision based on the pros and cons of each side.

I'm in the lighting industry, and man has there been a lot of sillyness with LED uptake. Great for driving demand and pushing LED research and manufacturing forward, but you get tired of explaining that no, maybe fluorescent or metal halide would be a better tool for some jobs. We're getting to a point where it'd be very infrequent for me to suggest them now, but the last couple of years...

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

[2] http://www.lighting-gallery.net/gallery/albums/userpics/1134...

!Agree

I'm very excited to have stumbled on this article on HN, as I am presently working on a project in this space; focusing on better ways to specify lighting needs and discuss light pollution's impact on terrestrial telescopes and astronomy.

Its neat to see that understanding consequences of artificial lighting, especially wrt. blue light content, is gaining awareness in the market.

I've been consulting with a company, that designs lighting whose spectral profile match specifications representative of ecological, industry, and human needs of a region.

The other advantage that LEDs have is that it's really easy to do efficient fixtures with full-cutoff (no direct uplight), since LEDs are a directional light source.

You can get that with HID sources too, but it means wrapping the whole thing in a reflector and having a flat lens on that bottom that doesn't drop below the housing: http://www.galleryoflights.org/mb/gallery/albums/userpics/IM...

It's really the decorative pedestrian-scale street lights where cutoff is a problem. People like their friendly/traditional looking lanterns and glowing spheres.

If the existing was the left side and the new was the right, would you feel the same way?

I would definitely feel a lot safer on the left side, which is one of the main goals of night lighting.

Your eyes adapt, though. Compare the shadow patches on the right side versus the shadow patches on the left. The left side is much clearer in the light patches, but the right is more consistent overall (supporting what cauterized says above about shadows).

Another sleeper issue with rapidly changing light and dark patches is that if you manage to get them to flicker around 10-14Hz (driving through light+dark patches), you're going to provoke the occasional photoresponsive epileptic seizure. This has been seen in some roads in France where the trees were spaced in such a way that when the sun is low in the sky, it creates such a flicker. I don't know what the rate would be for driving along that road at a normal rate, but I'd be curious to find out. If it's a relatively short road, it would be unlikely to flicker long enough to provoke a seizure, even in the right frequency ranges.

>Your eyes adapt, though.

Not to the point where one would feel as safe on the right as they do to the left.

>the right is more consistent overall

That's because of the fixtures--there's a reason they are causing lens flares while the left side isn't.

If "feels safe" is our goal, we're gonna be chasing those taillights forever. :/

I live on an incredibly well lit block in a very well lit part of SF. [0] I'm a couple of blocks away from a substantially less well lit block. [1] It's much more enjoyable to walk through the less well lit block than the more well lit ones. I expect that it's significantly nicer for the folks living in the apartments on that block, too.

Light pollution also affects people who aren't astronomers. :(

[0] Seriously, you can easily read a book on the street in just about any part of the TL. On my block, the fixtures are 50->75% as bright as daylight.

[1] That is to say, you'd have to strain your eyes to read a book on that section of the street.

>It's much more enjoyable to walk through the less well lit block than the more well lit ones.

I'm guessing this isn't the Tenderloin.

It's as much the North TL as my block is. The "dark" block is actually unique in the area; the surrounding blocks are significantly more well lit. You have to travel significantly deeper into Nob Hill to find more blocks that are that dark.

I often idly wonder if it's kept that dark because of the tranny (and non-trans [0]) hookers that work the area.

[0] Does it count as trans if it's only crossdressing? Labels are weird, man. :)

To the downvoters: You should understand that I don't see the drug dealers and prostitutes on the streets as a blight on the city, but rather as business men and women who are often rather pleasant to talk to. :-)

I strongly suspect that the TL is where dealers and prostitutes are encouraged to move to by the SFPD. (Largely because the TL turns into an open-air drug market around midday and an open-air drug and prostitution market towards the evening, and has continuously done so for the past ~5.5 years I've been living here.) This is -in my eyes- a positive feature rather than a bug.

>Seriously, you can easily read a book on the street in just about any part of the TL. On my block, the fixtures are 50->75% as bright as daylight.

I HIGHLY doubt that.Sunlight provides ~98,000 lux[1], while common street lighting is around 15 lux [2]

[1] https://en.wikipedia.org/wiki/Sunlight [2] https://www.use-ip.co.uk/datasheets/lux_light_level_chart.pd...

Perceived brightness after pupil dilation is what matters. If you can easily read a book then it's already too bright to sleep.

Am I the only one who doesn't feel safe when exposed to blindingly bright lights with lots of deep shadows around me?

I'd much prefer a more evenly lit road, with lights that don't blast away any night vision you might have.

> feel a lot safer

What's more important, perceived or actual safety?

Why would they be different in this scenario? One side is brighter with more accurate colors.

The article points out research that indicates that brighter lighting doesn't have a measurable effect on either crime or car safety.

I'm skeptical that there is enough data to be so sure.

Some say it's better for drivers avoiding pedestrians: http://www.osram.com/osram_com/news-and-knowledge/led-home/l...

While others say it makes them feel safer: http://www.treehugger.com/urban-design/friendly-streets-stud...

Does feeling safer matter? Increasing comfort is good, but it could also encourage more pedestrian activity and "eyes on the street" to dissuade crime as well.

Sure, feeling safer matters. But in a neighborhood that's already extremely safe and residents feel safe, you don't need glaring white lights to accomplish that. Slightly brighter lights than the sodium ones, sure. But "brighter" and "feels safer" can be accomplished while keeping them at a warm temperature and somewhere halfway up the scale from dim, instead of cranked all the way up to glaring.

Besides, as I mentioned in a previous comment, the blindingly deep shadows produced by the higher contrast of the bright lights makes me feel LESS safe because I now can make out less of what's around me.

And finally, feeling safe in and of itself doesn't have that much value, as anyone who disapproves of the TSA's security theater or the NSA's surveillance will gladly explain.

There is a photo "showing the difference in glare between poorly designed lamps and full cutoff lamps."

That reminds me of a lens design I read about back in 2013 that used TIR lenses

https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-21-9-10...

Anyone know if this system is seeing widespread adoption?

The advantage of light pollution is that you can get blown away if you do manage to find a dark spot in the countryside and see the night sky...

Here's an interesting art project that simulates what night skies would look like in cities without any artificial light: http://www.space.com/20615-darkened-cities-night-sky-imagine...

Totally fake. And obviously so. Wiki how many stars you can see them estimate how many are in the photo.

They're probably time-lapse photos. The captions don't say that a human observer would be able to see this much.

And openly so, as the artist combined pictures of cities with pictures of the night sky taken e.g. in the desert, but at the same latitude. So they are "fake" but plausible.

They're not plausible for a human, even out in the desert far from civilization. Light captured by a sensitive camera and long exposure do not represent what a human would see. Nearly all night time starscapes are enhanced past what a human would see in any situation.

Yeah, those photos seem to be a bit colorized with brighter than reality stars, but I'm willing to be overall density of visible stars would be the same.

A someone who spent considerable amount of time in his youth at dark sites observing with the naked eye, those pictures are not off by that much. To be fair, these are obviously pictures taken in very dry areas where there is no haze. But I have seen similar scenes with the naked eye in the winter before. I'm lucky enough to live in the countryside near the ocean and even though there is a fair amount of light pollution, in the winter I can go down to the beach and see the milky way in all its glory by looking out to sea. People really don't understand what they are missing. :-(

It's not that far off. You can see the Milky Way from the Adirondacks, about 200 miles from the first picture.

These have been made with 30 seconds exposures. But in dark places like Death Valley the sky looks pretty similar. You can easily see the band of the Milky Way with the naked eye.

Nightclubs have been ruined. Bright LEDs replace the old lines one for one, and instead of being dark, with bits of light it is almost like daylight.

I wrote a paper for a sociology class in college focussing not only on light pollution, but the fact that many historians believe that certain cultural and aesthetic attributes of cities and surrounding urban areas are lost when the warm glow of HPS lights is replaced with stark white LEDs.

If that's really a concern, LEDs don't have to be white.

Exactly this, I have seen "sodium" LED lights which replace HPS lights with a similar spectrum. Apparently this was to avoid replacing all of the lights at once, and by swapping them out as they burn out the city gets the full lifetime value of the bulbs. (yes the energy cost dwarfs that but not all cities want to front the upfront cost)

It's also helpful to have exterior LEDs that can change color on demand; for example, there are regulations in Florida on the coast as to what color lights you can use due to sea turtle nesting behaviors, but their nesting/mating is seasonal (and short window of time).

Kind of. The really high efficiency LEDs are blue. The problem is with the efficiency of green LEDs.

I suppose you could just use red and yellow LEDs and completely solve the circadian light problem. I think that such streetlights would be hard to sell.

You can cover the blue LEDs with yellow phosphor and get a subjectively "white" light, such as the Amazon Kindles. You could even cover that in a blue-reducing filter to make it much more yellow, but I don't know how bad the efficiency would be after all that.

> Kind of. The really high efficiency LEDs are blue. The problem is with the efficiency of green LEDs.

Hu? That's not true. Blue is less efficient, not more. The lower the wavelength the more efficient (toward the red side of the rainbow).

Also mono-color LEDs are MUCH more efficient than the ultraviolet ones with a phosphor (AKA white) ones.

If you wanted efficiency then have red and green in an LED, and that's it. You don't really need full color at night.

Each LED technology has an optimal wavelength. The current tendency is to use blue LEDs and then make white light with phosphors so the development is mostly on the blue LED technologies.

The green problem is caused by the lack of a technology. So you end up with bluish/green coming down from the blue side and yellowish/green when going up from the red side. That prevents really efficient RGB LEDs and makes the inefficient phosphor based white LEDs competitive. If you ever see a RGB LCD backlight you will see that there are more green LEDs than red or blue LEDs.

They don't. So why are so many municipalities installing the white ones, to the detriment of quality of life on residential blocks?

The same thing could have been said when we went from oil lamps to light bulbs.

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