I never liked the term BLOG - but it's here to stay.
I have written a lot of material for various discussion groups and some of these articles have proven to be somewhat popular - even argumentative. A lot of people have asked that we resurrect some of these. Since these articles helped form the raison d'être of our company, readers may like to know "where we came from".
Most reductions in light pollution and nuisance lighting can be achieved with minimizing glare. (It is hard to argue for an increase in glare.) and, to not allow light trespass. (It is hard to argue that a manager or landowner should impose their illumination on neighbours.)
The counter argument is that suitable luminaires are not available, but in fact they have been around for over 1½ decades.
Since LEDs are the "new thing", there should be a hard limit of NO correlated colour temperatures >3000K (2700K ± 300). This minimizes low ecological and human health impact. (It is hard to argue against human health.) By the end of the summer 2015 all major producers will have CCT of 3000K or less as an option (emitting <10% of light <500 nm - the same a HPS). And the IDA Dark Sky Friendly designation will be in full effect. (They posted this requirement at the summer's end of 2014 and gave companies 1-year to comply, they must removed this popular marketing attribute from all literature.)
Illumination levels should also be reduced, but it is not easy to defend a lower than IESNA recommendation. (However, some cities have decided to illuminate at about 1/2 IESNA levels when they use Full Cut-off luminaires - with no apparent increase in the rates of crime or accidents.) However, if the glare (<10% of the light in the glare zone) and light trespass (beyond property boundaries) criteria are followed, the impact of high illumination will be on the cost of electricity and the cost of large expensive light fixtures, which should be a good deterrent.
In my studies over the years I find it amazing how different people can be. They differ in more profound ways than just ethnicity. Our differences are more than skin deep. However research only becomes practical when you test the impact of only one variable at a time. This ensures we test a single phenomena, but it may limit the applicability of the results. And, practical constraints that limit the extent of the study may invalidate some results.
Here is an example. Our daytime vision uses three types of “cone” cells – one for each of the three basic colours (blue, yellow and red). Each cell of these three receptors has the same sensitivity to light, but that does not mean we see light the same. Our sensitivity to colour is a function of the “number” of each type of receptor. Our sensitivity to blue light is low because they make up only 6% of the total “cone cells”. However, yellow and red are more problematic.
The ratio of yellow to red cells can vary between individuals by, at least, 1.5:1 to 1:1.5! A number of published works state that we are 2X more sensitive to red than yellow light. This seems to have been due to earlier studies with a limited number of subjects. Personally, I have trouble seeing with red light. As an amateur astronomer, I was always told to use red light at night, so I did – even though I couldn’t see very much. I now know that I am one of those with relatively few red receptors.
A lot of studies are based on undergraduate university students who volunteer to be test subjects to help earn a credit or extra money, and it is VERY difficult to get more than a dozen or so students. (I was one of them.). (This biases the results to young, smart and relatively healthy individuals – not the average human.) So in many (?) cases the research results may not reflect humans as a whole and “common sense” that has developed over generations should carry more weight. (My grandmother always said that the sleep before midnight was the most important. We now know why.) [Modern “Big Data” sets may help with this as long as the test protocols are identical.]
However, we have also learned that just because “a lot of people” are fine with X-lux levels or X-spectrum of light does not mean that it is all right to impose these conditions on others. The wisest course is to minimise the disruption to the natural world – fore which we have evolved – a Hippocratic Oath for social planners.
Regarding a definition of a “disturbed” circadian rhythm (CR); a shifted phase can still have a significant impact if it puts the body out-of-step with constant social schedules and the natural environmental cycles. The ramifications can be severe depending on the behaviour or activity and the amount of the CR phase shift. A simple example most of us have all experienced is staying up late before a morning exam, or jet lag.
I define “low impact” as that which has minimal impact on wildlife and human health. We did a lot of work studying the effects of natural and artificial light at night. Interestingly – even the light of the Moon affects plants and animals, but with the Moon, these effects are cyclic whereas artificial light is constant. High-impact lighting affects almost all life including humans simply because the ecosystem evolved over the eons to tolerate and even exploit the anonymity provided by darkness. Changing the night environment alters the cues to normal behaviour and even the biochemistry of most life forms.
Low-impact does not mean no-impact, so care must be exercised when using light in an otherwise natural setting.
The attributes of light that affect the ecosystem are the spectrum, brightness, extent and timing. I have published a few works on this. The Lighting Research and Technology Journal has one of them (Lighting Res.Technol.2014;Vol 46:50–66).
We experimented with a “compliant” luminaire and found that it provided remarkably good visibility. We now sell these lights to ecologically sensitive areas that must cater to late-night visitors. Unfortunately, city managers have been told that they “must have” CRI>80 and “at least” IESNA illumination levels. They also think that the glare that results from most LED fixtures is “necessary” for visibility. In a limited number of situations this may be true but there are a lot of “half-truths” being spread around that confuse and dupe the uninformed.
Humans are well adapted to the environment so problems can result if we change it unless we are careful. We now know enough to do much better, but this requires a change in product promotion, which in some cases may demand "back-tracking" our marketing mantras.
The promotion of white light luminaries began with the desire to more effectively display colours and provide daytime "quality" lighting throughout the night. This trend has continued with the marketing of white CF and LED products. However, the industry's marketing machine is slower to react than the research and engineering departments, and this can result in "bad press" and potential loss of business as consumers learn more about the adverse impact of lighting products.
White light certainly shows off an automotive retail lot, but this "punch" is becoming subdued with the more ubiquitous use of white light. As more cities convert from an amber high-pressure Sodium lamps to white light we are loosing the colour contrast that is so important for advertising and urban navigation.
Within the last decade significant advances in medical knowledge have revealed the adverse affects of short wavelength light at night on human and animal health. However with the industry's focus on white, the current product lines provide no options to avoid these effects. It seems very few industry leaders know of the recent discovery of photochemical image of light on our health. This knowledge results from the discovery of detectors in our eyes that directly affect the nocturnal timing of our body functions. They are primarily affected by short wavelength (<500 nm) light, which makes light look white.
In speaking with the industry, LED light sources can be made to reduce the light's impact on our health, but these are not made available by most companies. PRomoting the non-white "amber" light would counter the marketing thrust for white outdoor lighting. The CSbG EcoLight is the only readily available alternative to white light luminaires.
Plants evolved to expect the spectrum of sunlight, though there are more specific colours that can do the job almost as well – but this is getting into the more complicated study of a plant's action spectrum. More important is the timing, or schedule of the light and what type of plant is being grown. Are the plants short-day, long-day or day-neutral? We usually assume plants want what we what. But in fact they don't. Indeed, what we want may not even be good for us?
A lot of research has been done on plants and the impact of nocturnal lighting. In some cases artificial lighting is used in green houses to enhance growth. Trees determine the season by the length of the night. If the night is short, then it must be summer. Artificial light at night (ALAN) in autumn “fools” the tree into thinking it is still summer (short dark period) and this can delay or inhibit its preparation for winter - leading to stress or death.
Of course this has to do primarily with temperate zone plants. Some plants are insensitive to ALAN and are not affected by ALAN. It gets down to the climatic zone and whether the plant is a “long-day plant, a short-day plant, or a day-neutral plant (you can Google these terms). The key point is that all life has evolved with a dark night. In the last century we have begun to illuminate the night and this has fundamentally changed the environment. The vegetation we see in a city is quite different from what we see in the country. We are only now (the last few decades) started to study and discover the adverse side effects of artificial light.
The CSbG EcoLight has a much lower effect on plants than white light at night. Its spectrum avoids the short wavelengths that partially mediate the plant's response to light.
Our society permits and even encourages citizens to do some “crazy things” that are well known to be really bad for us (driving cars fast, smoking, drinking, eating a lot, and so on). They are permitted because people choose to do them (it is a democracy). However as professionals, we should help encourage our clients to take a more constructive route. Just because we “want” something, does not mean we “need” it. Having kids teaches this lesson very quickly!
And so it is with outdoor lighting. Just because some citizens want to flood light their property all night long - regardless of its affect on their neighbours, does not mean that bylaws should permit it. The same argument applies to commercial lighting and municipal lighting.
People point to safety and security to justify the "need" to illuminate large areas but they ignore the adverse side effects, and selectively ignore published research to the contrary. Without an active security system, outdoor lighting does not protect your property; rather it puts it on display. Similarly, a pedestrian standing in a patch of light is not safe, they are on display and blind to what lurks in the shadows.
The CSbG EcoLight is well shielded to prevent light trespass. This also prevents the glare that can prevent people from looking "beyond" the light into the shadows.
Liability and litigation are often used to justify current hight-impact lighting policies. What surprised me, and others who have looked into it, is the lack of any litigation caused by lighting issues – even when it is attempted in association with a wider claim.
It is not surprising this is the case since we are inundated in the press with general “reports” about litigation. The law is also a rather complicated issue since there are different limits: negligence and gross negligence, nonfeasance, misfeasance and malfeasance, Governmental Immunity from Tort, the Anns Principle, the difference between “policy” and “operational” arguments, the weight of AASHTO guidelines, and so on. (I apologise for mixing jurisdictions, but this helps to make my case).
Even what we may consider to be common sense liability is complex since there are overriding laws that absolve actions of governments (federal and local) from liability. Our research has failed to find ANY successful lawsuit involving lighting – in Canada or the USA. Even a long burned out streetlight at the scene of a fatal accident involving a pedestrian did not result in the city from being found at fault.
One general conclusion is that if a lighting policy is in place, and it is reasonably followed, the city is not liable. This includes illumination at levels significantly below that of the IESNA guidelines.
This was in response to a posting in a "discussion" forum. Although this seems to be a marketing post, I feel I must point out the shortcomings of most current luminaires.
ALL manufacturers have focused on lumens/watt, but the quality of the illumination has suffered because of it. The “only” attribute most luminaires have that addresses sustainability is that if you replace very old lamps the user will save a lot of electricity – this is true. However, They do not do so well against new HPS luminaires.
Also, the white light is the most impactful spectrum you can use at night. It has been documented to degrade the ecological balance and has been shown, at one extreme to reduce human health, and at the other extreme there are very strong links to various aliments including hormonal cancers. So users may save a few dollars in electricity by at a significant environment and social cost. This is not “sustainable” in the general definition of the word.
I am familiar with a few XXXX products. The quality of the illumination on two applications was significantly reduced when they replaced the existing HPS luminaires. There was a significant increase in the glare and light trespass due to poor shielding. And the increase in illumination level actually increased electrical usage. Although other manufacturers are offering lower CCT LEDs, XXXX continues to insist on 4000K – claiming that lower temperatures “look yellow”. They definitely do not. You have to go to a CCT in the low 2000K range to begin to see “yellow” at typical road illumination levels.
So although “sustainability” is a honourable attribute, marketing “spin” has corrupted its true meaning.
Roadway luminaires are not in the centre of our vision but they still compromise visibility because of off-axis light scattered in windshields, eyeglasses and especially within our eyes. Even light sources more than 30-degrees from our viewing axis compromise our vision due to thes effects and bleaching our rod cells.
Luminaires that use the ovoid lens to scatter light create glare in this way. The Full Cut-Off (FCO) luminaires are MUCH better. However most LED fixtures can be worse than the older HID FCO luminaires. On several demonstration projects the glare from the LEDs was, in my opinion – terrible. And, these were not cheep luminaires!
Although the manufacturers claimed they were FCO, the amount of light that was emitted in the 80 to 90 degree from nadir glare zone seemed to be much more than the 10% limit. This may have been due to the high perception of glare that is caused by white light, or the data was “massaged”.
I understand that luminaires approved for Hawaii are closer to Sharp Cut-off with much less than 10% in the glare zone, and our luminaire has similar shielding. (Virtually no light shines beyond the target area.)
So proper shielding can be incorporated but the metrics used to rate luminaires do not adequately take good shielding into account. Manufacturers with good shielding for their luminaires cannot compete in the typical urban market because of “hardwired” requirements for higher-glare fixtures. The best some of us can do is to demonstrate our products and let municipal engineers judge if their city would benefit from less glare.
Astronomers have always used red light when they needed to see better at night without undermining their night vision. This worked well with red-filtered incandescent lamps, but the new red LEDs work very differently, and this age-old advice is no longer helpful.
Incandescent bulbs emit a broad range of wavelengths beginning in the blue and increasing across the visual spectrum through the red and into the infrared. Filtering out what little blue light there was still a broad enough spectrum to be seen by most of the daylight colour receptor cells in the retina – the L-cones (red sensitive) and M-cones (yellow sensitive). These account for about 94% of all the cone-cells in the retina and provide good visual acuity for reading. Some people have more L-cones tan red-cones while other people have the opposite mix.
Red LEDs emit a narrow band of red light that can be seen by only the L-cones. This reduces our visual acuity to less than ½ that for filtered incandescent light.
Amber LEDs can be seen by both the L- and M-cones and so preserves our visual acuity. Our sensitive night vision cells also detect this light, and it will affect our night vision, but this is also a good thing. Much less light is needed to read and recognize shapes with amber light than with red LEDs.
You may read more about this in a paper I published in Sky and Telescope Magazine for June 2016.
Glare from a light fixture is inevitable but understanding where it
comes from can be helpful in reducing its impact.
The key point is the need for good optics. Without reasonable optics, the light distribution is lambertian (it is bright perpendicular to the fixture’s window, which then decreases closer to the horizon), and the 1/r2 decrease in the illumination on the ground with distance. Optics can at least partially compensate for these two terms.
In my experiments, I identify two regions in the illumination pattern, which are somewhat defined by the location of the observer. One involves the luminance (brightness) of the luminaire and the other the luminance of the ground.
With the observer in the main illuminated area (target area), the lamp of the luminaire is visible and produces a lot of glare. This light is illuminating the ground. As you walk away from the luminaire, eventually the sharp cut-off of [my] luminaire hides the lamps and reduces the glare to nearly zero. However, the light that shines “below” my eyes continues out to illuminate 25% to 50% farther from the luminaire. The ratio of the "glare distance" to "illumination distance" is related to the height of the observer's eyes, and the mounting height of the luminaire. The glare will usually be less for a walking pedestrian than a sitting motorist. Either way, the shielding of the luminaire should put this glare as far from the “centre of our field of view” as practical.
Another contribution to glare is the apparent size of the light source. Spreading out the light in the fixture and thereby reducing the apparent intensity of the source will reduce the visual impact of the glare. This can be done with well designed diffusers. Instead of seeing a single bright spot or array of bright spots - as produced by typical LED luminaires, the observer would see a glowing patch.
So this suggests a different perspective. If you are in the target area, then you will see the lamp and experience glare. The key point in glare control is to ensure that the lamp is only visible from the target area and not many “pole heights” down the road or second story bedroom windows, where the contribution to illumination is minimal and the glare approaches the centre of our vision.