
LED Light Pollution: Can We Save Energy and Save the Night? (2015) - rfreytag
http://spie.org/newsroom/1015-led-light-pollution
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cauterized
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.

~~~
21
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](https://i.imgur.com/e0nReZ8.jpg)

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

~~~
cauterized
Wow, that's an unpleasant effect!

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post_break
Higher kelvin lights look so much better in my opinion.
[http://i.imgur.com/XHqUPOY.jpg](http://i.imgur.com/XHqUPOY.jpg)

~~~
bluthru
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.

~~~
vacri
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.

~~~
bluthru
>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.

~~~
simoncion
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.

~~~
mmel
>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](https://en.wikipedia.org/wiki/Sunlight)
[2] [https://www.use-
ip.co.uk/datasheets/lux_light_level_chart.pd...](https://www.use-
ip.co.uk/datasheets/lux_light_level_chart.pdf)

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

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clumsysmurf
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...](https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-21-9-10612&id=253009)

Anyone know if this system is seeing widespread adoption?

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f_allwein
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...](http://www.space.com/20615-darkened-cities-night-sky-
imagined.html)

~~~
aaron695
Totally fake. And obviously so. Wiki how many stars you can see them estimate
how many are in the photo.

~~~
f_allwein
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.

~~~
koube
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.

~~~
ImprovedSilence
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.

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stuaxo
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.

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arcaster
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.

~~~
sp332
If that's really a concern, LEDs don't have to be white.

~~~
upofadown
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.

~~~
ars
> 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.

~~~
upofadown
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.

