I had a recent look at the JW Speaker catalogue. There's at least a whole page dedicated to explaining color temperature. In it includes some color temperature ranges. Under the 3000K and less range the description, "Can fatigue eyes and make people feel tired" is given. Additionally, 5000K is promoted for improving driver "alertness" and "safety". I was under the impression that Mr. Speaker and his company were generally against this trend towards the blue. Has something changed? Has any research come out in support of high blue content white light for headlights?
J.W. Speaker Denouncing Low-CCT White Light?
- Thread starter cetary35
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5000K LED's in my flashlights most closely resemble sunlight from high in the sky. Sounds like a good choice for driving.
According to repeated studies from UMTRI, higher blue content 4000K HID and 4000K and above LED generated more glare. Their research showed the highest color temperature lights produced the worst glare. There was also more research done at earlier dates that showed similar results.
Furthermore, according to Daniel Stern, blue light is one of the least helpful colors of light at night. It tends to focus in front of our retinas rather then upon them. I've also, anecdotally, did the blue light test that Mr. Stern was talking about in the article. I used a blue pump SST-20 flashlight that I built. When I tried to see things in the dark with blue, objects did indeed appear to blur. So we have this 5000K LED light, whose spectral power is nothing like the sun, not even providing much useful light for the viewer.
All this is why I'm a bit upset with with J.W. Speaker at the moment.
No, they don't. Most 5000K LED's have a large blue spike and very little deep red. Their spectral power looks nothing like the sun. Even the highest end Optisolis emitters still have a pronounced blue spike.
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I wonder if they are influenced by any biased studies funded by an established industry.
I know that high output is cheaper and easier to achieve using cooler CCT. Im sure automotive lighting engineers will use whatever cost saving measures to meet both vehicle price point and legal requirements for headlights, and they aren't as concerned about quality of vision. As evidenced by the downright dangerous headlights on some vehicles, checking the box seems more important than meeting an arbitrary bar set by lighting enthusiasts, because not enough of their customers are asking for it.
I know that high output is cheaper and easier to achieve using cooler CCT. Im sure automotive lighting engineers will use whatever cost saving measures to meet both vehicle price point and legal requirements for headlights, and they aren't as concerned about quality of vision. As evidenced by the downright dangerous headlights on some vehicles, checking the box seems more important than meeting an arbitrary bar set by lighting enthusiasts, because not enough of their customers are asking for it.
(Seems like no one here is thinking those blueish headlights are useful)
My eyes must see different than yours, cetary. Spectral graphs certainly provide information but actually looking with one's eyes is what counts. Warmer CCT yields inferior contrast for me (warmer than ~4200K). If indeed cooler/more blue light keeps more people awake/alert, then that should over rule belief/opinion in graphs. How many times have night drivers fallen asleep at the wheel?
My eyes must see different than yours, cetary. Spectral graphs certainly provide information but actually looking with one's eyes is what counts. Warmer CCT yields inferior contrast for me (warmer than ~4200K). If indeed cooler/more blue light keeps more people awake/alert, then that should over rule belief/opinion in graphs. How many times have night drivers fallen asleep at the wheel?
5000k Flashlights are the worst, I have several "warm white" flashlights that I bought back around 2011-2012 from a company called Xeno, they use warm white Cree XML chips, and closely resemble halogen light color temperature. Much more pleasant and useful.
With 5000k light color rendering is horrible. For instance when I am grilling outside at night, I can't tell the readiness of the meat on the grille because the color is off.
With 5000k light color rendering is horrible. For instance when I am grilling outside at night, I can't tell the readiness of the meat on the grille because the color is off.
jtr1962
Flashaholic
Many studies have been done on visual acuity versus color temperature. Here are a few:
http://www.naturalux.com/High Color Temperature Lighting School Children_Highlighted.pdf
https://www.researchgate.net/public...he_Color_Temperature_of_the_Surround_Lighting
You want higher CCTs for headlights/streetlights to improve visual acuity, depth perception, and peripheral vision. Peripheral vision is important at urban driving speeds of 15 to 30 mph, but it's still useful even at highway speeds.
If we're talking about indoor lighting then in many cases it doesn't matter as much if you're optimizing seeing. Here it simply boils down to aesthetic preference. Obviously the ideal CCT can vary even for the same individual, depending upon the application, but I've found it doesn't vary by much, at least for me. I consider 5000K ideal. No matter where I'm lighting, once I get down to 4500K it starts to seem a little too warm but still tolerable (i.e. the Nichia 219s I modded one of my LED bulbs with). On the other hand, getting much over 6500K with any light source is too cool. I seem to tolerate higher CCT with LED sources as opposed to fluorescent, but 6500K is my limit even with LED. I think for most inidividuals there is a tolerance band. I highly doubt anyone who prefers, say, 2700K can tolerate 5000K at all, regardless of setting. And someone like me who prefers 5000K won't find any setting where they would want 3000K, or even 4000K. Low CCT causes me fatigue, along with diminished ability to see clearly.
Color rendering is another issue. The orthodoxy for headlights/streetlights, which I disagree with, is that CRI doesn't matter so long as it's at least around 70. For example, the blue spike mentioned is more of an issue with lower CRI LEDs. By definition the spike is much smaller as you reach CRI in the 90s for the simple reason it has to be. There's no way to have a large blue spike, and fudge the rest of the spectrum, which still obtaining a 90+ CRI. I suspect the concern with efficiency is the reason why we gloss over CRI for headlights, and especially streetlights. However, anecdotally I've found equivalent seeing at lower lux levels using higher CRI LEDs of the the same CCT as lower CRI. In theory then you could use high CRI, lower the illumination levels, get the same amount of visual benefit, and use about the same amount of power. Even better, the blue spike will now be much smaller due to the spectrum itself, and the lowered intensity. I'm unaware of any studies done on this subject, but I think it lends itself to one. I'd like to see the industry move solely to high CRI LEDs, both for indoor and outdoor lighting. At this point even with efficiency penalties relative to low CRI you're still at ~150 lm/W for CRI 90+.
Those who complain about lousy color rendering of ~5000K LEDs need to try CRI 95+ versions. You'll be able to cook steak just fine, and you'll also be able to render cooler colors accurately, which is something low CCT LEDs fail miserably at.
http://www.naturalux.com/High Color Temperature Lighting School Children_Highlighted.pdf
https://www.researchgate.net/public...he_Color_Temperature_of_the_Surround_Lighting
You want higher CCTs for headlights/streetlights to improve visual acuity, depth perception, and peripheral vision. Peripheral vision is important at urban driving speeds of 15 to 30 mph, but it's still useful even at highway speeds.
If we're talking about indoor lighting then in many cases it doesn't matter as much if you're optimizing seeing. Here it simply boils down to aesthetic preference. Obviously the ideal CCT can vary even for the same individual, depending upon the application, but I've found it doesn't vary by much, at least for me. I consider 5000K ideal. No matter where I'm lighting, once I get down to 4500K it starts to seem a little too warm but still tolerable (i.e. the Nichia 219s I modded one of my LED bulbs with). On the other hand, getting much over 6500K with any light source is too cool. I seem to tolerate higher CCT with LED sources as opposed to fluorescent, but 6500K is my limit even with LED. I think for most inidividuals there is a tolerance band. I highly doubt anyone who prefers, say, 2700K can tolerate 5000K at all, regardless of setting. And someone like me who prefers 5000K won't find any setting where they would want 3000K, or even 4000K. Low CCT causes me fatigue, along with diminished ability to see clearly.
Color rendering is another issue. The orthodoxy for headlights/streetlights, which I disagree with, is that CRI doesn't matter so long as it's at least around 70. For example, the blue spike mentioned is more of an issue with lower CRI LEDs. By definition the spike is much smaller as you reach CRI in the 90s for the simple reason it has to be. There's no way to have a large blue spike, and fudge the rest of the spectrum, which still obtaining a 90+ CRI. I suspect the concern with efficiency is the reason why we gloss over CRI for headlights, and especially streetlights. However, anecdotally I've found equivalent seeing at lower lux levels using higher CRI LEDs of the the same CCT as lower CRI. In theory then you could use high CRI, lower the illumination levels, get the same amount of visual benefit, and use about the same amount of power. Even better, the blue spike will now be much smaller due to the spectrum itself, and the lowered intensity. I'm unaware of any studies done on this subject, but I think it lends itself to one. I'd like to see the industry move solely to high CRI LEDs, both for indoor and outdoor lighting. At this point even with efficiency penalties relative to low CRI you're still at ~150 lm/W for CRI 90+.
Those who complain about lousy color rendering of ~5000K LEDs need to try CRI 95+ versions. You'll be able to cook steak just fine, and you'll also be able to render cooler colors accurately, which is something low CCT LEDs fail miserably at.
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jtr1962
Flashaholic
Same with me. I HATE anything much warmer than 4000K for the same reasons.
And yes, we want drivers to be wide awake at night. High CCT lighting helps in that regard.
LED Color Chart | Temperature Differences, 6000K, 5000K LED
Color of the LEDs is influenced by many factors, such as materials, construction and type of LED chips they use. Our experts explain the most popular LED colors and specs. Keep reading to find out the LED temperature differences, info on how to understand color chart and see comparison of 6000K...
halo-headlights.com
I'm not as much concerned about what shade of brown the buffalo is standing in the road 100 meters away as I am seeing there's a buffalo standing in the road 100 meters away...
But if the buffalo is standing in front of a brownish background, good color rendering could make the difference between an effective swerve or a totaled vehicle.
I recently acquired a Fraz Labs flashlight with that Hi CRI Samsung 351 (or other) that is 5000K and when shining it during the day (sun is relatively high) it is a very similar color temperature and rendering to the cast of the sun. Using firelight flashlights (4000K is not really firelight color temperature) at night, life seems more pleasant and comfortable, right?
I recently acquired a Fraz Labs flashlight with that Hi CRI Samsung 351 (or other) that is 5000K and when shining it during the day (sun is relatively high) it is a very similar color temperature and rendering to the cast of the sun. Using firelight flashlights (4000K is not really firelight color temperature) at night, life seems more pleasant and comfortable, right?
Your studies aren't about driving. The only car headlight related study that promoted the use of blue-enriched white light was one done by Sylvania that showed a near insiginificant improvment in seeing ability in the out of focus periphery.
This study done by Nancy Clanton showed the highest CCT LED street lights performing nearly the worst in target detection tests. The visibility tests involved taking people as passengers in a moving car and having them visually identify objects on the road surface. The test speed was 30mph. The 4500K LED performed nearly the worst. The 3500K LED in Test sites 4 & 5 and the 3000K induction at test site 1 performed the best. This study is much more immediately relevant to driving then children sitting in a classroom, and this study is more recent to. It also tests newer lighting technologies out in actual streets. The tested seeing distances, at only 18 inches, of your studies isn't reflective of the seeing distances of driving either.
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kerneldrop
Flashlight Enthusiast
^^ can I like this 22,348,997 times?
I seriously doubt that.
In my office I have "Neutral while" fixtures, they are pure while around 4100-4300k. At home everything is soft/warm white, around 3000k. I absolute can not tolerate 5000k anywhere except headlights, and even then I preferred 4100K HIDs over current trend of 5000k LEDs.
I think most street lamps around here in NYC are actually 4300K LEDs. Not sure about their CRI rating, but they are much better than old high pressure sodium lamps or mercury lamps that they used in the past.
I don't know how many, if any, flashlights out there are available with high CRI. There are barely ever any warm white flashlights anymore to be found. I have my favorite warm white Xeno flashlight, with a removable diffuser, its super versatile, I absolutely love it and use it all the time. It is probably 75-80 CRI, but for a flashlight the quality of light is excellent.
Back to JW Speaker, their products are certainly on a warmer spectrum. I have a JW Speaker adaptive headlight on my motorcycle, along with a set of cheap chinese passing lights, and the headlight is visibly warmer - probably around 4100k vs 5000k on the passing lights.
jtr1962
Flashaholic
We're not talking about blue-enriched white light, whatever that's supposed to mean. We're talking about white light, which generally is accepted to mean broad spectrum illumination in the range of ~3000K to 6500K. On the lower ends of that, most people perceive "white" light to be yellowish, while they perceive the high ends to be bluish. The center, generally from 4500K to 5500K, is perceived by most as pure white. This also happens to be the CCT which the human visual system was designed to operate optimally at, whether for close-up or distance seeing.
Now here's where it gets interesting. You have the human eye photopic and scotopic responses. In between is the mesopic response, which is relevant to headlights and streetlights.
Photopic, Mesopic and Scotopic: Definitions and Relevance to Lighting Calculations
Summary: The terms photopic, mesopic and scotopic refer to three ranges of human vision adaptation level, which differ in anatomical response, spectrum and their effect on visual acuity. The Illuminating Engineering Society of North America (IE...
support.agi32.com
Research has found that white light that is "cool" in appearance, with more energy in the short-wavelength (blue-violet) part of the spectrum, appears to be brighter than white light that is "warm" in appearance, with more energy in the longer (orange-red) part of the spectrum.
Research has also shown that at medium-to-high (photopic) light levels it is easier to discern small details under a light source that has more blue in the spectrum (cooler in appearance).
Finally, in several experiments at mesopic light levels, researchers have compared foveal vision and peripheral vision under HPS and MH luminaires at mesopic levels. They found that the color of the light source didn't affect direct vision, the ability to see details when looking directly at the object. However, in a simulated roadway application (no vehicles to run over the subjects!) where they tested peripheral vision, they found that the subjects had faster reaction times under MH than under HPS, all other conditions being equal. Unlike the effects found at medium and high light levels, this is a rod effect; the rods, most responsible for our peripheral vision, are more sensitive to the "cooler" wavelengths of the MH lamp.
The study you linked to appears to be designed to support what was already a foregone conclusion, namely that 3000K streetlighting is best because that's what the city of SD decided to require. I can tell you right now that this type of lighting is lousy compared to, say, 4500K, based on my personal experience with it. NYC installed LED streetlights starting in the mid 2010s. The standardized on low 4000s, maybe 4200K or 4500K, I forgot which. This was a huge improvement over the former high-pressure sodium, which killed peripheral vision, gave everything a flat, non 3D appearance, and made the citiscape appear dirty and yellow. Unfortunately, because some of the new fixtures were either excessively bright, or had light trespass, a vocal minority complained. They associated the whiter light with the problems, not the higher intensity or optics of the fixtures. As a result, the city put in 3000K on many side blocks, although it thankfully kept the whiter lights on major arterials and highways. Big mistake. For any given intensity, 3000K looks dimmer. And it results in reduced peripheral vision, depth perception, and visual acuity compared to the original LED lights. I'm not the only one who feels that way:
Street-light CCT debate will continue, but it is misguided (MAGAZINE)
Maury Wright deliberates over the continued debate surrounding LED street light CCT and outdoor lighting guidance that has been offered by multiple parties.
www.ledsmagazine.com
We have written about the debate over LED street-light color temperature or CCT. I remain convinced that cooler CCTs, perhaps in the 4000K range, are optimum because I believe we see better at night under such conditions.
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jtr1962
Flashaholic
The 4300K LEDs are great. Unfortunately, they changed the lights on some side streets to 3000K for misguided reasons. People were associating valid complaints like light trespass due to poor fixture design, or excessive intensity, with "whiter" light. A minority of complainers forced the change on the rest of us, even though some surveys showed most liked the 4300K better. Thankfully they at least kept them on the arterials. Now I'm trying to get them to switch them back on the side streets, my reason being public safety. I can't see as well with the 3000K lights, both because they're lower wattage and lower color temperature.
I'm barely old enough to remember the mercury lamps. Those got switched out in the early 1970s. Almost everyone immediately complained about how awful and dim the high-pressure sodium were.
