3 ms·

>and for any bulbs bluer than about 2500K CCT, ends up being awful at night. How so? And as I've posted previously, you probably shouldn't use anything below ~

>and for any bulbs bluer than about 2500K CCT, ends up being awful at night. How so? And as I've posted previously, you probably shouldn't use anything below ~4000K anyway if you want to have healthy eyes.

jacobolus 11y ago
Light in the blue part of the spectrum is very distracting in peripheral vision and causes more glare because it saturates rod and short-wavelength cone photoreceptors, and it causes the eyes to adapt to an expected higher light level, which wipes out night vision. For both drivers and pedestrians, blue-wavelength glare impedes vision into the shadows, causes distraction, and slows reaction times. If you want more reasons not to have blue-wavelength outdoor lighting at night, it also disrupts melatonin production and sleep rhythms causing all sorts of human health problems, heavily disrupts wildlife circadian rhythms (both animals and plants), and creates more light pollution, making life dreary for skygazers and amateur astronomers. The best outdoor lighting is low-pressure sodium lamps. High-pressure sodium lamps, “warm” incandescent lamps, and LEDs at a CCT of ~2000–2500K are also not too terrible, especially if well shielded and not too bright: In general outdoor lighting can safely be much dimmer than most cities make it, because human vision can adapt to extremely low light levels just fine. Bright white LEDs of ≥3500K CCT are absolutely awful outdoor nighttime lighting: unpleasant, unhealthy, environmentally destructive, and wasteful of energy. For more info, see http://www.csbg.ca/articles/APPLIED_SCOTOBIOLOGY.PDF http://www.csbg.ca/articles/APPLIED_SCOTOBIOLOGY.PDF and http://darksky.org/wp-content/uploads/bsk-pdf-manager/8_IDA-BLUE-RICH-LIGHT-WHITE-PAPER.PDF http://darksky.org/wp-content/uploads/bsk-pdf-manager/8_IDA-... (and the rest of http://darksky.org http://darksky.org)
- PepeGomez 11y ago
  Almost none of that is true, or it's only true if the lighting is designed incorrectly. Try to try it for yourself. The recommendation of using red light to preserve night vision is mostly a myth. While at the same absolute brightness red light indeed reduces night vission less, you need a much more powerful red light source to reach the same subjective brightness, which cancels out any potential benefit. The same is true for outdoor lighting. The eye is the most sensitive to ~505 nm blue-green light, so you need much dimmer white/blue-green light sources to reach equal visibility with orange ones, which both saves energy and reduces light polution. White LEDs are only a problem where no compensation was made for their higher subjective brightness. When LED lighting is used correctly, it's quite pleasant and it looks kind of like unusually good moonlight. No you can't use dim orange/"warm white" lights, because human vision can't night adapt to them, it needs the short wavelenghts for that which are missing from these light sources. It's not true that high color temperature LEDs are wasteful, on the contrary, low color temperature LEDs are inherently less efficient. Warm white will always be less efficient than more bluish light and there is nothing that can be done about that, since it's a feature of our vision. And what I meant in my previous comment is that it's likely that the exposure to unnaturally low color temperature light is what causes nearsightedness: http://www.nature.com/news/the-myopia-boom-1.17120 http://www.nature.com/news/the-myopia-boom-1.17120 and http://iovs.arvojournals.org/article.aspx?articleid=2127682 http://iovs.arvojournals.org/article.aspx?articleid=2127682
  - jacobolus 11y ago
    I’ve just spent several months researching this topic, and doing lots of informal experiments on myself and other people. In other words, I have tried it for myself. :-) If you’re somewhere in the SF Bay Area and want to discuss in more detail, I’d be happy to give a mini-lecture about the subject, or about human color vision more generally. At the typical brightness of streetlamps outdoors in most cities, humans are using photopic rather than scotopic vision (that is, using the “medium” and “long” cone photoreceptors), which is fairly sensitive to anything between about 500–650 nm. For photopic vision, the bright blue spike of a white LED provides almost no useful contribution to brightness perception. Under starlight or moonlight and no artificial lights, you would be correct, but that’s not the condition we’re discussing. If outdoor lamps cast no more total light in aggregate than the moon, then bluer wavelengths would be fine. In practice they are several orders of magnitude brighter than the moon, which means they saturate the rods and mostly wipe out scotopic vision. The cause of the nearsightedness epidemic (e.g. in East Asia) is children not going outside in the sun during the day. The details of the lamps they use at night (indoors or outdoors) are irrelevant to that. I became interested in this topic because the streetlamps on my street were replaced by white LEDs at ~4000K CCT, and they are truly awful. They cause extreme amounts of peripheral-vision glare, and they make the previously charming street feel like a prison yard or sad industrial warehouse. The previous high-pressure sodium lamps are so so soooo much better.
    - PepeGomez 11y ago
      > the typical brightness of streetlamps outdoors in most cities, humans are using photopic rather than scotopic vision Becase they would be useless otherwise. Take a 650nm led and a 500nm led and try turning them down slowly. The 650nm one will just go off with very limited, if any, dark adaptation. You will be able to see the led glowing, but the room won't seem to be illuminated. With the 500nm light, there will be a wide range to which the eye can adapt easily. >The cause of the nearsightedness epidemic (e.g. in East Asia) is children not going outside in the sun during the day. The details of the lamps they use at night (indoors or outdoors) are irrelevant to that. The evidence for light chromaticity seems to be more convincing. It's supported by animal models and it provides a plausible mechanism. The light intensity on the other hand is suggested by nothing but weak correlation, which could be bacause children who spend more time outside are on average exposed to less yellow light. You can have a rising/setting sun in your peripheral vision without it feeling unpleasent, the lights are either way too bright, poorly constructed or there is something wrong with your eyes. (a cataract maybe?)

jacobolus 11y ago

Light in the blue part of the spectrum is very distracting in peripheral vision and causes more glare because it saturates rod and short-wavelength cone photoreceptors, and it causes the eyes to adapt to an expected higher light level, which wipes out night vision. For both drivers and pedestrians, blue-wavelength glare impedes vision into the shadows, causes distraction, and slows reaction times. If you want more reasons not to have blue-wavelength outdoor lighting at night, it also disrupts melatonin production and sleep rhythms causing all sorts of human health problems, heavily disrupts wildlife circadian rhythms (both animals and plants), and creates more light pollution, making life dreary for skygazers and amateur astronomers. The best outdoor lighting is low-pressure sodium lamps. High-pressure sodium lamps, “warm” incandescent lamps, and LEDs at a CCT of ~2000–2500K are also not too terrible, especially if well shielded and not too bright: In general outdoor lighting can safely be much dimmer than most cities make it, because human vision can adapt to extremely low light levels just fine. Bright white LEDs of ≥3500K CCT are absolutely awful outdoor nighttime lighting: unpleasant, unhealthy, environmentally destructive, and wasteful of energy. For more info, see http://www.csbg.ca/articles/APPLIED_SCOTOBIOLOGY.PDF http://www.csbg.ca/articles/APPLIED_SCOTOBIOLOGY.PDF and http://darksky.org/wp-content/uploads/bsk-pdf-manager/8_IDA-BLUE-RICH-LIGHT-WHITE-PAPER.PDF http://darksky.org/wp-content/uploads/bsk-pdf-manager/8_IDA-... (and the rest of http://darksky.org http://darksky.org)

PepeGomez 11y ago
Almost none of that is true, or it's only true if the lighting is designed incorrectly. Try to try it for yourself. The recommendation of using red light to preserve night vision is mostly a myth. While at the same absolute brightness red light indeed reduces night vission less, you need a much more powerful red light source to reach the same subjective brightness, which cancels out any potential benefit. The same is true for outdoor lighting. The eye is the most sensitive to ~505 nm blue-green light, so you need much dimmer white/blue-green light sources to reach equal visibility with orange ones, which both saves energy and reduces light polution. White LEDs are only a problem where no compensation was made for their higher subjective brightness. When LED lighting is used correctly, it's quite pleasant and it looks kind of like unusually good moonlight. No you can't use dim orange/"warm white" lights, because human vision can't night adapt to them, it needs the short wavelenghts for that which are missing from these light sources. It's not true that high color temperature LEDs are wasteful, on the contrary, low color temperature LEDs are inherently less efficient. Warm white will always be less efficient than more bluish light and there is nothing that can be done about that, since it's a feature of our vision. And what I meant in my previous comment is that it's likely that the exposure to unnaturally low color temperature light is what causes nearsightedness: http://www.nature.com/news/the-myopia-boom-1.17120 http://www.nature.com/news/the-myopia-boom-1.17120 and http://iovs.arvojournals.org/article.aspx?articleid=2127682 http://iovs.arvojournals.org/article.aspx?articleid=2127682
- jacobolus 11y ago
  I’ve just spent several months researching this topic, and doing lots of informal experiments on myself and other people. In other words, I have tried it for myself. :-) If you’re somewhere in the SF Bay Area and want to discuss in more detail, I’d be happy to give a mini-lecture about the subject, or about human color vision more generally. At the typical brightness of streetlamps outdoors in most cities, humans are using photopic rather than scotopic vision (that is, using the “medium” and “long” cone photoreceptors), which is fairly sensitive to anything between about 500–650 nm. For photopic vision, the bright blue spike of a white LED provides almost no useful contribution to brightness perception. Under starlight or moonlight and no artificial lights, you would be correct, but that’s not the condition we’re discussing. If outdoor lamps cast no more total light in aggregate than the moon, then bluer wavelengths would be fine. In practice they are several orders of magnitude brighter than the moon, which means they saturate the rods and mostly wipe out scotopic vision. The cause of the nearsightedness epidemic (e.g. in East Asia) is children not going outside in the sun during the day. The details of the lamps they use at night (indoors or outdoors) are irrelevant to that. I became interested in this topic because the streetlamps on my street were replaced by white LEDs at ~4000K CCT, and they are truly awful. They cause extreme amounts of peripheral-vision glare, and they make the previously charming street feel like a prison yard or sad industrial warehouse. The previous high-pressure sodium lamps are so so soooo much better.
  - PepeGomez 11y ago
    > the typical brightness of streetlamps outdoors in most cities, humans are using photopic rather than scotopic vision Becase they would be useless otherwise. Take a 650nm led and a 500nm led and try turning them down slowly. The 650nm one will just go off with very limited, if any, dark adaptation. You will be able to see the led glowing, but the room won't seem to be illuminated. With the 500nm light, there will be a wide range to which the eye can adapt easily. >The cause of the nearsightedness epidemic (e.g. in East Asia) is children not going outside in the sun during the day. The details of the lamps they use at night (indoors or outdoors) are irrelevant to that. The evidence for light chromaticity seems to be more convincing. It's supported by animal models and it provides a plausible mechanism. The light intensity on the other hand is suggested by nothing but weak correlation, which could be bacause children who spend more time outside are on average exposed to less yellow light. You can have a rising/setting sun in your peripheral vision without it feeling unpleasent, the lights are either way too bright, poorly constructed or there is something wrong with your eyes. (a cataract maybe?)