I have unread negative comments about this sloppy writing.
They also repeatedly use the word "intense" incorrectly. Intensity refers to candela. Not lumens or temperature.
> The original LED streetlights had temperatures of at least 4000K, which produces a bright white light with a high content of unseen blue light.
4000K is actually considered fairly mellow. Above 6000K, then things start to get blue. The earliest white LEDs were around 10000K and terrible.
> Now, however, LEDs are available with lower kelvin ratings and roughly the same energy efficiency as those with higher ratings.
And now the higher kelvin lights are even more efficient. White LEDs use phosphors to shift the blue light to longer wavelengths. This is a lossy process. Low-K tints require more phosphors and reduce efficiency. That said, 4000K looks so much nicer than 6000K that the loss is worth it.
> “As a species, we weren’t designed to see light at night,” Siminovitch said.
We've had mastery over fire for as long as we've been a species. Darkness is unnatural to humans.
Moonlight is around 4100K. So it is even more "natural" than 3000K. Should we blot out the moon next?
> it urged cities to minimize blue-rich outside lighting and recommended the use of LEDs no brighter than 3000K.
Confusing color temperature and brightness again.
And now from the AMA's press release:
> Recent large surveys found that brighter residential nighttime lighting is associated with reduced sleep times, [etc]
It seems no one has blinds in their windows. I always carry an eye-mask with me too, just in case.
The AMA press release is very low on actual content so I can't comment on most of it. They are smart enough to avoid mentioning the "blue light causes eye damage" myth for example, sticking to meaningless wishy-washy statements.
If the people raising a fuss over LEDs actually cared, they would have been campaigning against mercury-vapor and high-intensity-discharge lamps for the past several decades. A 4000K LED puts out way less blue light than either of those technologies.
> Moonlight is around 4100K. So it is even more "natural" than 3000K. Should we blot out the moon next?
I was on a hike in July during a full moon and those who were sleeping in open air (no tent or bivy bag) struggled to sleep through the night due to the moonlight.
This was in the North West of Australia, so daytime maximums were around 35C. It was too warm at night to zip your tent or bivy closed, so where possible you would try to position yourself so that you could shield yourself from the moonlight during the night.
There were quite a few afternoon nappers in the group until the moon waned a little by the second week.
Perhaps this is our bodies telling us something, a piece of our evolution. Perhaps we aren't meant to sleep in the open. We are easy prey at night. Sleeping in moonlight, out in the open, is dangerous for prey animals. A dislike for sleeping in moonlight might therefore be a survival tool. Those uncomfortable with moonlight were more likely to be sleeping under cover and less likely to be hauled off by lions.
Even worse is the extreme latitudes in summer! I tried sleeping under just a mosquito net in Alaska when the sun stayed up until 2am and rose again by 4. I brought a sleeping mask but found it hard to keep on, as we'd encountered three separate grizzlies earlier that day…
At lower latitudes, a full moon over snow is stunning and surreal when you can get away from local light sources - no flashlight required. Light at night (of appropriate color temp) is quite natural.
I sleep in a hammock on my balcony quite a bit and without covering your eyes it can be a real struggle when the moon is near full and the skies are clear. One thing mentioned elsewhere is the idea that darkness = safety. I can imagine that to be very true for humans.
I would also submit that Kelvin is not an appropriate reference for the colour of LED lights. Kelvin only makes sense when discussing blackbody emissions, it is essentially a description of temperature. LEDs do not create light via simple heating. Their spectrum is not the smooth blackbody curve that the kelvin scale suggests. It is in fact a combination of several strong emissions at narrow wavelengths that combine to fool our senses into perceiving white light.
Proper discussion of harmful emissions from LEDs should instead speak of intensities at a particular wavelength and perhaps ratios between wavelengths rather than an outdated reference designed for blackbodies.
While I agree with you from a standpoint of accuracy, Kelvin is still really useful. It also happens to map pretty nicely to how we perceive color.
The N-step MacAdam ellipse on a 2D CCx/CCy plane is what gets used when you dig into tint, but people love to reduce complex systems to a single number. And if you want a single number, temperature is the best we have.
I'm curious what your suggestion might look like in practice because it would be even more complex than the MacAdam ellipse.
In practice, I could see a simple description of the intensity of visible along with a percentage of the 'bad' light within that intensity. That is an analog for how our eyes actually function. We have a retina that sees specific wavelengths, but an iris that regulates the amount of light hitting the retina based on an average intensity across the visible spectrum.
Harm comes to our eyes when 'unnatural' non-blackbody light plays tricks with the system. Looking at an eclipse isn't harmful because of some new light that only exists during an eclipse. It's because the darkness allows our iris to open despite the presence of harmful UV light. (The same goes for vintage sunglasses that don't block UV.) So to discuss the biological safety of light one needs, at a minimum, both the average intensity to judge how open the iris will be, and some reference for how much harmful light is present. Imho that can be expressed as an intensity and a percentage. An eclipse is a low visible intensity with a high percentage of harmful light. These blue-heavy LEDs could be similarly described.
CRI accounts for this, though it does not reveal the specific wavelength components. You can however be confident a 90+ CRI light source is not going to have an unexpectedly high intensity of any given wavelength.
What matters isn't color temperature, but the presence or absence of light in the range 360-405 nanometers, which activates certain neurons in the retina that suppress melatonin secretion. This light can be "unseen" because visual receptors don't respond particularly strongly to it, so it can be masked by much stronger emissions of yellow light. However, it still has an effect. Color perception is irrelevant in this case.
405nm is violet. 360nm is UV. Yes, we are sensitive to it. But white LEDs emit none* of either.
*Future generation of LEDs might shift from indigo (445nm) to violet to improve color rendition, but cost will go way up and efficiency will go way down so I doubt it will be common. And some stores are already adding UV LEDs to their lighting in order to make florescents really pop.
My city used old-style mercury-vapor street lights up until the early 80s. For those who have never seen these lights, they have a bluish-white appearance but emit light only at a few very specific wavelengths, and almost none in the red spectrum. The effect is that under these lights a red car would look strangely black while everything else more or less looked normal color. I loved the effect.
I have fond childhood memories of seeing my street bathed in the bluish-white light from these street lights, especially during those long winter nights when the ground is covered in white snow. I am quite certain that these street lights did not produce a generation of "physiologically unwell" people.
My city has now begun switching to LED lights and I think they look terrific.
These mercury-vapor lamps were used until 90-somethings where i used to live. People would say that until these bluish-white lamps were phased out by orange ones, people in the street would look as if they were dead; I would always counter with "they sure look as if they're alive now". Maybe because of childhood nostalgia I always preferred the bluish-white nights instead of that pervasive orange ones, especially during overcast winter nights where everything in thirty kilometer radius would become orange and unnatural. Clear nights with full moon were godsend.
But things are changing nowadays and our city also started using LEDs and by Moses, they are so much unbelievably better in all aspects! Even if they emit that "unseen blue" light, it is most definitely not worse than the insanely pervasive orange...
This is an obnoxiously dismissive comment build on ignorance and shoddy reasoning and an “I don’t care what you think just suck it up and stop complaining” approach to design/policy.
The moon is one (1) singular source of light with a known peak intensity, often blocked by trees or clouds, and only at its brightest one day every month. On a full moon night, the moon is high overhead, not directly in your field of view if you’re looking straight ahead.
LED streetlamps are a dozen or more point light sources, directly in the field of view, each one of them individually brighter than the moon. The 4000K LED streetlamps installed on my street last year have a very sharp spike in the short wavelength part of their spectral power distribution (come to my street and I’ll lend you some diffraction grating glasses to see the spectrum for yourself). The LED lamps are also incredibly bright, I’d say 2–4x the luminance of the prior streetlamps or the sodium lamps on nearby streets.
Because the new lamps are brighter, cities save money by using fewer of them, spaced more widely. This causes the light to be less even than past streetlamps, meaning some parts of the street are intensely illuminated and other parts are in shadows. The lamps are shielded at the top, but they shine out to the side at a very wide angle, meaning they still cause a ton of glare from a block away or more. When originally installed they had poor shielding in the direction of people’s second-floor bedroom windows. They’ve since fixed that problem and only people on the first floor still have light shining directly into their windows.
Seeing these and objects they illuminate in your peripheral vision causes the eyes to become bright-adapted (i.e. entirely knocks out night vision) making objects in shadow appear darker than under other lighting, and the whole scene to have very high contrast. (It takes something like a half hour to become dark-adapted once again.) The glare is extremely distracting. Overall they make the street feel like an industrial warehouse.
The light is not like fire, or past streetlamps.
Beyond that, the new lamps are not more energy efficient than modern sodium lamps. Indeed, if you make them more than twice as bright, they use substantially more energy than well made sodium lamps.
When I walk my dog at night I’ve taken to wearing orange safety glasses (basically plastic filters which block out the short-wavelength part of the spectrum). That I can see noticeably better after blocking half the light put out by these streetlamps indicates that there is some problem with their current design. (With the orange glasses, my rod vision continues to function properly.)
LED streetlamps should be at ~2700K CCT or below, with almost no light in the blue part of the spectrum. They should be no brighter than past streetlamps. They should be placed close together and not too high up, and shielded to mostly direct their light downward rather than sideways.
Under such circumstances they would be fine. (LEDs aren’t an inherently bad technology. They have the advantage that they last longer without needing to be replaced. This saves money for city maintenance departments.) Unfortunately current models on the market don’t meet those criteria.
Same story for car headlamps. The current LED headlamps are a safety risk (blinding pedestrians and other drivers with the glare). LED technology could be used to make fine car headlamps; it’s the ones currently on the market that are terrible.
Yes, I was a little glib. But nonetheless life on Earth (not just our species) evolved with a 4100K light source at night.
You are confusing color temperature with how the lights are installed. If your streetlights were 4000K and spaced properly you wouldn't have an issue with them. The penny-pinching distribution (high lumens, wide angle, distantly spaced) of lights chosen by your city is at fault. That layout will create maximum glare and is the most miserable layout imaginable since distant lights will always be shining directly in your eyes.
I have spent 10 years studying color science. I know what color temperature is. I’m just explaining why the moon is a poor analogy. I have an issue with bright short-wavelength light sources at night, regardless of lamp configuration. It knocks out night vision.
There is a wide literature (dozens if not hundreds of research papers) on this topic. It’s not exactly some deep mystery.
The lamp configuration just makes things worse (and the use of fewer, brighter lamps provides much of the economic incentive to install the new lamps, along with federal subsidies).
Do you mean that there are places where street lights with other technologies are replaced with LEDs by leaving every other lamp post empty?
That is a problem that LEDs could enable (by making very bright lamps available) but is not really a problem of LEDs but a problem of using any bright light source wrongly.
My understanding is that the use of lower-energy and more durable light sources provide most of the incentive to install new lamps. I.e. electricity bill is lower and you need to change the lamps less frequently which reduces maintenance cost.
They rip the poles out, and replace them with fewer new poles (taller, wider spaced, with brighter lamps).
This makes the installation cost more attractive to the city.
The electricity bill is (potentially) lower if you replace very old lamps with LEDs at the same brightness.
The best sodium lamps are quite efficient though, so LEDs have only marginal advantage compared to replacing the old lamps with newer sodium lamps. If you make the LEDs dramatically brighter, then they actually end up using more electricity.
I haven’t seen any especially convincing numbers about an LED lamp project that saved on electricity bills. I’m not an expert in the subject though, and I haven’t looked too deeply into digging up data.
As others have noted, we sleep poorly under strong moonlight.
I live in a very rural wooded area, and I can leave my blinds open except when the moon is at its brightest -- I sleep very poorly if I don't use blackout curtains.
Perhaps the fittest humans were the ones who stayed the most awake and aware of nocturnal predators during the brightest nights of the month?
Noticed in my parents' town with their recent deployment. The LED lights appear to be more tunable and/or actually tuned, to put light on the street while keeping it off of houses.
So, "blue" whatever. If you are keeping my yard dark so I don't have to pull the shades just to block out the light, well, win!
Of course, other areas that still feel the need to light up every square centimeter because security, YMMV.
I'll add that I find the current LED streetlight colors better than the orange sodium vapor "malaise" that we've grown so accustomed to.
"It is estimated that a “white” LED lamp is at least 5 times more powerful in influencing circadian physiology than a high pressure sodium light
based on melatonin suppression. Recent large surveys found that brighter residential nighttime
lighting is associated with reduced sleep time, dissatisfaction with sleep quality, nighttime
awakenings, excessive sleepiness, impaired daytime functioning, and obesity. Thus, white LED
street lighting patterns also could contribute to the risk of chronic disease in the populations of
cities in which they have been installed. Measurements at street level from white LED street lamps
are needed to more accurately assess the potential circadian impact of evening/nighttime exposure
to these lights."
This follows tit-for-tat the story of every other street lighting development in the past. It gets invented, implemented, lauded and then disappointment sets in. At least according to a fairly exhaustive book on the topic called Disenchanted Night: The Industrialization of Light in the Nineteenth Century[1]
No. The lights aren't effective at keeping sleepy people more awake in the moment. They're effective at disrupting sleep over time by disrupting the hormonal system.
They should be banned in favor of lower-color-temperature lights.
It's not exactly banning an outdoor light so much as regulating outdoor lights for the sake of public health.
And yes, it is reasonable to do so. For one, everyone's got to share the same streetlights. For two, if these lights really are harmful to sleep, then the cost of using lights that are engineered to not produce certain wavelengths is probably minuscule compared to the net public benefit, even if you only want to limit the criteria being considered to things that are easily assigned a cash value.
Mandating Flux on phones, on the other hand, is a very different proposition in every way but the most superficial of similarities. People can make their own decisions about their phone's color scheme, and those decisions don't really affect anyone else in any direct way.
Maybe it's just me, but Twilight never felt as pleasant as f.lux and redshift do on my PCs. Instead of changing the screen color, it seems to add a red layer over the content.
If you've got a phone supported by CyanogenMod, it has a very nice mode called "LiveDisplay" which will adjust the phone screen's colour temperature on the fly based on time of day and both the brightness and colour of the ambient light.
As phrased, it also sounds really far-fetched since cataracts are not a disease of the retina. Maybe that's a problem with the phrasing and not the claim, though.
I think there's some miscommunication here. Certainly, it's possible for light to damage the retina. It's likely that blue light is more apt to cause damage because it's higher energy. This doesn't mean that LEDs producing a larger blue component are more damaging than LEDs (or other lights) with a smaller blue component. It's entirely possible that at the intensity artificial light is used for indoor and street lighting, how much of the light is blue is irrelevant.
I didn't read this entire article, but it seems to be discussing the general mechanism of light damage. There was no reference to LEDs. I'd want to see something that gave reason to believe that the blue in LEDs poses a threat.
Edit:Adding LED to the search results in many spurious sources in 1st two pages, with a single NIH study. Again, more reading required:
http://ehp.niehs.nih.gov/122-a81/
This particular topic falls into the same category as 'phone radiation & brain cancer' news, where claims are made, proven, disproven and so on. If either proves true enough, we'll all be in the same boat together, I guess.
just look up 'welders eye' or 'corneal flash burns' or 'photokeratitis'
high intensity UV light most certainly causes both corneal and retinal damage, both acute and as an ongoing effect over time.
i have never seen nor can i find any reference to visible blue light. i think* that heavily phosphored leds with high CRI and low color temp do emit quite heavily above visible and translate it down. so maybe there is some leakage?
No one disputes that sufficient light can damage the eye. The question is whether there's any evidence that LEDs cause damage to the eye sure to the higher percentage of blue light.
The fact that exposure to extreme amounts of light can damage the eye is not evidence for the claim that LEDs at typical brightness damage the eye.
I'm not an eye doctor. It was explained to me that LEDs output blue wavelengths not present in the natural environment. Our eyes filter out many wavelengths but never saw these during evolution so the light goes right through their filters. The energy then dissipates in your eye and causes damage.
I thought this was already common around the world, say in Europe.
Where 4 lane / artery / highways get brighter, whiter (bluer) lights, while 2 lane feeders and smaller roads have warmer yellow lighting.
It produces an interesting nighttime aerial effect as the color indicates the nature of the street.
I can't find any source to corroborate so I'd love if someone with more worldly travel experience could corroborate.
I first became aware of the phenomenon playing Cities: Skylines, a European developed city builder game which features the multi-colored street lights in European skins.
IDK, but this could simply be an effect of bigger roads getting more frequent upgrades, and/or bigger roads tolerating a larger cost per light since the total cost per meter of road is already higher.
Have more faith in European engineering and regulation, it's something we excel at :-)
There are 9 grades of lighting, ranging from that required on a motorway interchange, through urban motorways, rural motorways, major roads, etc, to residential areas.
I'm head of engineering for a company that designs outdoor luminaires for industrial environments, but not street lights. We use LED and other technologies. Like so many things in life, there are aspects of the AMA directive with potential cause for concern, but also combined with a mixed bag of scientific underpinnings. If you have specific questions about LED physics or human vision, I'm happy to give them a go. I also can speak to some of the literature behind the AMA position paper.
Essentially any LED bulb that you can buy is a blue diode with a down conversion phosphor. The composition of the phosphor, and the relative amount of blue light vs. phosphor emissions shape our perception of color temperature for these LED sources.
Due to an effect called metamerism, our brains can perceive the same apparent color from sources with different underlying spectral power distributions (power vs. wavelength).
So in a sense, the color temperature of a black body does not have much underlying connection with the spectral power distribution of LED lamps.
With that substantial caveat, the lower the correlated color temperature of the bulbs that you purchase, the less of the overall spectral power is from the diode, and the more from the phosphors.
If there ends up being a link to blue light exposure for circadian effects then bulbs with lower CCT that have more emission from the phosphors are the safer bet.
I second this recommendation, although it is worth pointing out that they are not that bright even on full. Fine for going to bed but maybe not the only thing you want on a cloudy day. The sunset mode is really nice too, and I really really wish there was a way to hold at the pink color when it is nearly off. If you could get strips of that color to circle the room that would be excellent.
The flip side of lights that disrupt melatonin is that they can be good for you when you first wake up if natural light is not that strong in the morning where you are (or you aren't exposed to much of it when you first wake up).
While that may improve sleep, it may also made driving less safe. With blue light it is easy for eyes to focus. In fact there is a theory that significant increase in myopia during the last 100 years is caused by eye work under artificial light without blue color, like from ordinary light bulb...
Edit: I should have written "without blue light in spectrum eyes work harder". Basically any deviation from the spectrum of Sun have cosequences for eyes performance long term
Apart from psychological effects, there is no reason why blue light should be easier to focus (the change in refractive index for different wavelengths is marginal).
I've worked on a few street light retrofit projects and the AMA warning is a little overblown and frankly immediately outdated.
This is off the cuff, but it comes down to circadian rhythms being influenced by the color of light. Before artficial light, the sunrise and sunset have a softer light with a lot more red wavelength in it. This would correspond more closely with the color of light from an incandescent, like 2500-3000 Kelvin. The mid day light has a lot more blue wavelength in it relatively, where it is much more of a White light, I think daylight is like 15,000K. The high pressure sodium, HPS, lights have an orange light in the 2,200K range. The majority of LED street lights being installed are 4000-5000K, so they have a lot more of the blue light. Essentially the blue light tricks your brain into thinking it's mid day and messes with your sleep patterns.
The first generations of LED street lights could really only effectively make the 4000-5000K light. With new generations coming out every 3 months or so though they have been able to create models that can generate the 2500-3000K warm red light, but they're not quite as energy efficienct as the 4000K lamps, maybe 10% or something. The 2500K is actually better for the Dark Sky movements as well and a lot of cities are moving to specify these warmer temperature for those reasons.
There are a whole bunch of other things going on as well. The road way lighting standards were designed around the light patterns of a HPS lamp and haven't been updated to reflect the light patterns possible with LEDs, hence a lot of LED projects have too bright of streets.
For the sleep pattern issues, when you're installing LED lights in your home, you want to put the warm lamps, 2500-3000K, lamps in bedrooms and such. Then for living spaces or offices you'd want to put the 4000K lamps to help keep you awake during the day. There are also lamps/fixtures available that will automatically tune the color output of the light to be in sync with the outdoors to help keep circadian rhythms in sync.
> This is off the cuff, but it comes down to circadian rhythms being influenced by the color of light. Before artficial light, the sunrise and sunset have a softer light with a lot more red wavelength in it.
That is right, which is why I have a nice project to use a heliostat with optical fibre to use as daylighting for a house interior.
The colour temperature shall have a nice warm glow in early morning and evening, which shall aid sleep preparation. I'll publish a log if I believe the project is successful.
Set it and forget it is the best smart house technology.
It's got nothing to do with intensity, which would be impossible to achieve, for all practical purposes. The article misused the word here. Rather, it's about color temperature.
I think this problem is overblown, because I've not heard similar complaints leveled against mercury-vapour lamps. I've grown up around them nearly all my life.
When you replace 1:1 vapor laps with LEDs an adequately lit parking lot becomes lit like a stage.
Though to your color temp point, if we could get lower color temperature that'd be great. IIRC red LEDs are much more efficient than full spectrum anyway.
All the studies I've found seem to say something along the lines of "blue light disturbs sleep", which seems like exactly the needed effect if you're driving at night.
The light has an effect during the night as it blocks the melatonin hormone from kicking in. It takes about an hour of darkness for the hormone kick in and make you sleepy. On very long occasional drives it's probably safer to trade some sleep disturbance for a more wakeful drive. If it's your daily commute it'll probably mess up your sleep.
Somewhat related, I've always wondered why outdoor solid shutters or blinds are a given in some countries/regions but nowhere to be seen in others, even though some residential areas are extremely polluted by artificial light at night.
Those were historically used to prevent damage to window panes, not block light. They are popular in areas that were settled when glass was very fragile/expensive and receive strong winds. Pre-glass, they were used to keep weather from blowing through the house.
I had LEDs installed in the streetlight in front of my apartment in Brooklyn a few months ago and my living room is now awash with this light. It's terrible. I noticed my sleep time pushed further and further back and I've resorted to supplementing melatonin regularly so that I can fall asleep earlier than 2 am. I've complained to the city and have considered moving since I don't think NYC will swap ours back.
Please, put in blinds. If you have blinds, put in curtains to catch the light that spills around the blinds. If too much light goes through the blinds, upgrade to window shades. If that isn't enough (or you don't want to spend any money on interior decorating), get an eyemask. If $2 for an eyemask is too much, drape a t-shirt over your eyes.
I don't find it unreasonable to want to have my curtains and windows open after sundown.
My bedroom is at the back of the house and feels like a cave, as is common for NYC bedrooms, so it's not the light in my eyes that is the issue. Having a delayed melatonin release due to the light is more my concern.
That's assuming city services go to all neighborhoods evenly, which certainly isn't the case unfortunately. Most of Brooklyn is covered now, but only 1/3 of Queens and none of The Bronx other than highways have been converted.
Because of your eye's sensitivity to different frequencies, the "warmer" colors require more energy for the same effective lighting. Hence, highway departments choose the "daylight" option to save energy.
I'm sure the LED manufacturers will take full advantage of this opportunity to create "true-light healthy LEDs", for which they can charge double or triple.
You can already get some (actually really nice) LEDs for your house that change color to lower temperature (more orange/red) as they dim, mimicking the effect of dimming incandescents. It does make for a nice cozy atmosphere. As you say, they're not cheap, but I'd consider them strongly if I were redecorating.
Edit: it's confusing that a cool blue light is a high temperature, and a warm orange light is a low temperature.
It is a confusing story, and not well supported by actual facts or studies. So I wonder about these things, who has it in for street lights? Crooks obviously it makes their life harder (and it mentions in the article that police are getting better witness descriptions under LED lights). And presumably the folks who made the old Mercury Vapor lights. Which happen to have about 1/10th the cost to make as LED lights but seem to sell for the same amount, so perhaps their margins are getting squeezed uncomfortably. Power companies of course, who could depend on the electricity load coming from inefficient street lights finding that one of their biggest consumer at their lowest utilization time is cutting their power requirements by 33% or more. That has to hurt you really don't want to turn off base load during the night. And of course people who liked the look of their street before and now are sad because it looks different[1].
[1] When people switched from coal fireplaces to gas heat a common complaint was that it didn't smell like home any more.
I remember reading here in Pittsburgh that the new street lights could be addressed individually or as groups and have their white points adjusted. I've never seen this in action and I haven't researched it further. But if they could be adjusted to be less blue, we'd still benefit from the energy savings.
Given that white LEDs rely on blue LED components, and blue LEDs are the most expensive and most delicate parts in these lights, one would think lowering the blue content should be a no brainer. More comfortable and cheaper all around.
I've had it with "warm, yellow" street lights. Redwood City, CA standardized on low-pressure sodium lamps decades ago. Other than the Golden Gate Bridge, almost nobody uses those deep yellow lamps any more. (The Golden Gate Bridge switched to high-pressure sodium in the 1970s, and LEDs recently, but put in amber lenses to maintain the old color.) Redwood City is finally going LED, and streets look much brighter.
I think they mean that there is a lot of blue light emitted, but it is not super obvious because they emit longer wavelength light as well (reds & greens).
Wouldn't filters or rough refraction surface help offset the risks? Of course, I kind of feel that in climates with snowfall, the bulbs that generate heat are probably better for keeping said snow from building on the street lamps/lights.
I'm not sure what the point was in the first place? Sodium lamps approach 200 lumens/watt. LEDs are whiter, but whiter light doesn't necessarily help you drive, does it? If the concern is colored signs, light the signs?
> unseen blue light
I have unread negative comments about this sloppy writing.
They also repeatedly use the word "intense" incorrectly. Intensity refers to candela. Not lumens or temperature.
> The original LED streetlights had temperatures of at least 4000K, which produces a bright white light with a high content of unseen blue light.
4000K is actually considered fairly mellow. Above 6000K, then things start to get blue. The earliest white LEDs were around 10000K and terrible.
> Now, however, LEDs are available with lower kelvin ratings and roughly the same energy efficiency as those with higher ratings.
And now the higher kelvin lights are even more efficient. White LEDs use phosphors to shift the blue light to longer wavelengths. This is a lossy process. Low-K tints require more phosphors and reduce efficiency. That said, 4000K looks so much nicer than 6000K that the loss is worth it.
> “As a species, we weren’t designed to see light at night,” Siminovitch said.
We've had mastery over fire for as long as we've been a species. Darkness is unnatural to humans.
Moonlight is around 4100K. So it is even more "natural" than 3000K. Should we blot out the moon next?
> it urged cities to minimize blue-rich outside lighting and recommended the use of LEDs no brighter than 3000K.
Confusing color temperature and brightness again.
And now from the AMA's press release:
> Recent large surveys found that brighter residential nighttime lighting is associated with reduced sleep times, [etc]
It seems no one has blinds in their windows. I always carry an eye-mask with me too, just in case.
The AMA press release is very low on actual content so I can't comment on most of it. They are smart enough to avoid mentioning the "blue light causes eye damage" myth for example, sticking to meaningless wishy-washy statements.
If the people raising a fuss over LEDs actually cared, they would have been campaigning against mercury-vapor and high-intensity-discharge lamps for the past several decades. A 4000K LED puts out way less blue light than either of those technologies.