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Some cities are taking another look at LED lighting after AMA warning

washingtonpost.com

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Re: Some cities are taking another look at LED lighting after AMA warning

#51

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…

What temperature LED light should I have for my bedroom?

I have a Philips sunrise alarm clock that looks like a lamp.

I recommend that. It is a great lamp colour temperature and way to wake up.

Re: Some cities are taking another look at LED lighting after AMA warning

#52

I've worked on a few street light retrofit projects and the AMA warning is a little overblown and frankly immediately outdated.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…

> 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.

Re: Some cities are taking another look at LED lighting after AMA warning

#53
post #29

Let's break down their claims. > 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 6…

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.

Re: Some cities are taking another look at LED lighting after AMA warning

#54
post #46
post #15

Earlier quoted context omitted.

The blue light also burns out retinae. It's been linked to cataracts. It seems like an industrial regulation is needed to me.

Citation? That's a bold claim. 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.

A quick goog of blue+light+retina+study brings up quite a few legit sites. The one I am going to read for my edification on the subject:

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3144654/

Re: Some cities are taking another look at LED lighting after AMA warning

#55
post #21
post #12

Earlier quoted context omitted.

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.

>They should be banned in favor of lower-color-temperature lights. As the article indicates, they are less effective at disrupting sleep than a LCD monitor or smartphone. If we're banning an outdoor light for being less disruptive than your phone, should we also mandate Flux style warm color phones at night by law?

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.

Re: Some cities are taking another look at LED lighting after AMA warning

#56
post #50

Earlier quoted context omitted.

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…

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 p…

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.

Re: Some cities are taking another look at LED lighting after AMA warning

#57

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…

What temperature LED light should I have for my bedroom?

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.

Re: Some cities are taking another look at LED lighting after AMA warning

#58

Yes! I am not crazy! Seriously, do we really need lights that make the city as light as in the day? I'd rather give my retinas a rest.

> as light as in the day

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.

Re: Some cities are taking another look at LED lighting after AMA warning

#59

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.

Re: Some cities are taking another look at LED lighting after AMA warning

#60
post #46
post #15

Earlier quoted context omitted.

The blue light also burns out retinae. It's been linked to cataracts. It seems like an industrial regulation is needed to me.

Citation? That's a bold claim. 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'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.
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