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Thread: "Whiter" headlamps...CCT, CRI, SPD?

  1. #1
    Moderator Alaric Darconville's Avatar
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    Default "Whiter" headlamps...CCT, CRI, SPD?

    This thread split off from Ford Fusion LED headlamp discussion, trivial argument removed to focus on the meat of the matter.
    Last edited by -Virgil-; 10-02-2016 at 12:16 PM.

  2. #2

    Default Re: "Whiter" headlights...CCT, CRI, SPD?

    There is no single color that is defined as white, at least insofar as what the regulations say white is. White is the range of color that falls within the boundaries defined by FMVSS 108, to wit,

    White (achromatic). The color of light emitted must fall within the following boundaries:
    x = 0.31 (blue boundary)
    y = 0.44 (green boundary)
    x = 0.50 (yellow boundary)
    y = 0.15 + 0.64x (green boundary)
    y = 0.38 (red boundary)
    y = 0.05 + 0.75x (purple boundary)

    It looks something like this (closest graphic I could quickly find):


    But then, I rather suspect you knew all of that...

    Tom


    Last edited by -Virgil-; 10-02-2016 at 12:12 PM. Reason: clarification

  3. #3

    Default Re: "Whiter" headlights...CCT, CRI, SPD?

    FMVSS/SAE defines white light however everyone understands what the term "more white" means and many people not well versed in lighting are going to be absolutely confused when you tell them no white light can be whiter than another. Even reputable lighting companies like Osram use the term "whiter" when refering to higher CCTs in their descriptions meant for the general public and therefore I continue to use it too.
    Last edited by -Virgil-; 10-02-2016 at 12:13 PM.

  4. #4

    Default Re: "Whiter" headlights...CCT, CRI, SPD?

    It seems to me that such sensitivity actually lessens the opportunities for teachable moments and understanding among the newcomers.

    .33/.33 is considerably whiter than .50/.44. It might be beneficial to talk about the color spectrum that is 'allowable white'. There certainly are headlights that are whiter than others, legally so as in the case of compliant HID vs OEM halogen.

    Strident protest does not make it not so.

    Tom
    Last edited by -Virgil-; 10-02-2016 at 12:13 PM.

  5. #5

    Default Re: "Whiter" headlights...CCT, CRI, SPD?

    Quote Originally Posted by souperdoo View Post
    It seems to me that such sensitivity actually lessens the opportunities for teachable moments and understanding among the newcomers.

    .33/.33 is considerably whiter than .50/.44. It might be beneficial to talk about the color spectrum that is 'allowable white'. There certainly are headlights that are whiter than others, legally so as in the case of compliant HID vs OEM halogen.

    Strident protest does not make it not so.

    Tom
    You are exactly correct. I went and checked and both Philips and Osram use the term "whiter light" in their product descriptions, and that is a term that most people understand. People are not always speaking in deeply technical terms as found in the relevant SAE/FMVSS 108 portions. For all practical purposes getting down to such a strict level of accuracy is difficult when engaging in everyday conversations on a forum, and off-putting for new comers. Infact most people don't even know what CCT is let alone the exact coordinates of white light specified by SAE.

    There is nothing wrong with pointing out that in technical documents its not called "whiter light" but rather higher or lower CCT, but to just state blankly " No white light is whiter than any other white light." is really a useless statement when it is not accompanied by an explanation, or an acknowledgment that your point was understood.


    Last edited by -Virgil-; 10-02-2016 at 12:14 PM.

  6. #6

    Default Re: "Whiter" headlights...CCT, CRI, SPD?

    CCT may be the easiest, and somewhat more precise, way to convey the color of light. At least within a given context. I think a newcomer may be better able to grasp the idea of something glowing as it is heated to a given temperature more easily than they can envision a given set of Cartesian coordinates in a chromacity diagram.

    There is the conundrum that 8000K is 'cooler' than 4000K. That terminology should be stricken, as it is really 'kewler'...

    I find headlights that are greater than 4000K start to get uncomfortable for me at night. Daytime is no bother.

    Tom
    Last edited by -Virgil-; 10-02-2016 at 12:14 PM.

  7. #7

    Default Re: "Whiter" headlights...CCT, CRI, SPD?

    Quote Originally Posted by Magio View Post
    I went and checked and both Philips and Osram use the term "whiter light" in their product descriptions
    Promotional material playing fast and loose with words and stretching the boundaries of the truth is not a new phenomenon. Philips and Osram also use phrases like "closer to natural daylight" in their product descriptions -- talk about stretching the boundaries of the truth. It's not realistic to say "Well, it's here in the product descriptions, so it's legitimate". That's a non-sequitur; the second thing doesn't follow on from the first.

    and that is a term that most people understand
    I would say it's a term that many people think they understand, but in fact their idea of what that term means is exactly what the marketers who wrote it want the consumers who read it to think it means. The lighting world is littered with words, terms, and phrases like this. "Full spectrum", "Closer to natural sunlight/daylight/skylight", etc.

    All that said, there is a legitimate use of the phrase "whiter light" that is readily understandable to people who don't know (or want to know) anything technical about light: it means light with less of a color cast than some other light. That could be less-orange, less-yellow, less-violet, less-blue, less-red, etc. But mostly that's not how it's used to sell lights. Mostly it's used disingenuously to refer to light that is equally or more colored than the comparison light, but in a different direction. Less-orange and more blue, for example. And that is not, in any real sense of the word, "whiter" -- it is bluer, which is most consumers' (deliberately faulty) "understanding" of what "whiter light" means.

    It really doesn't serve anyone (except the marketers and their employers) to perpetuate a falsehood on the grounds that a lot of people don't know any better than to believe it.

    CCT may be the easiest, and somewhat more precise, way to convey the color of light. At least within a given context.
    If what we care about is how the operating lamp looks when we observe it, then yes, we should talk about CCT. If what we care about is how things look when lit by the lamp, then no, we need to be talking about CRI and if we need to get more specific than that, we need to be talking about SPD.
    Last edited by -Virgil-; 10-02-2016 at 12:14 PM.

  8. #8

    Default Re: "Whiter" headlights...CCT, CRI, SPD?

    Quote Originally Posted by -Virgil- View Post
    All that said, there is a legitimate use of the phrase "whiter light" that is readily understandable to people who don't know (or want to know) anything technical about light: it means light with less of a color cast than some other light. That could be less-orange, less-yellow, less-violet, less-blue, less-red, etc.
    I can honestly say that whenever I have used the phrase "whiter light"( and what I have always thought that phrase meant) I have always had reference to the definition that the CIE gives to white light as a "colour stimulus that an observer who is adapted to the viewing environment would judge to be perfectly achromatic and to have a luminance factor of unity." In other words when I used the phrase "whiter light" I was reffering to a light source that was more nearly achromatic than a comparable light source, which is a legitimate usage of the phrase. I have never used it to refer to blue lights, or green lights, and I most definitely agree with you that that is an improper usage of the phrase.
    Last edited by -Virgil-; 10-02-2016 at 12:14 PM.

  9. #9

    Default Re: "Whiter" headlights...CCT, CRI, SPD?

    Quote Originally Posted by Magio View Post
    I can honestly say that whenever I have used the phrase "whiter light"( and what I have always thought that phrase meant) (...) I was reffering to a light source that was more nearly achromatic than a comparable light source, which is a legitimate usage of the phrase.
    Yes, it is.

    I have never used it to refer to blue lights
    Well, there's no need for that situation to continue...just sign on with Philips or Osram or any of the other makers as a marketer, and you, too, can earn money for convincing people that bluer lights are "whiter"!
    Last edited by -Virgil-; 10-02-2016 at 12:14 PM.

  10. #10

    Default Re: "Whiter" headlights...CCT, CRI, SPD?

    Quote Originally Posted by -Virgil- View Post
    just sign on with Philips or Osram or any of the other makers as a marketer, and you, too, can earn money for convincing people that bluer lights are "whiter"!
    Not interested in going down that rabbit hole, even though it pays good LOL
    Last edited by -Virgil-; 10-02-2016 at 12:14 PM.

  11. #11
    Flashaholic Marcturus's Avatar
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    Default Re: "Whiter" headlights...CCT, CRI, SPD?

    Quote Originally Posted by Magio View Post
    Not interested in going down that rabbit hole, even though it pays good LOL
    One has to wonder if they really do work in a fog-free office environment...
    "Thanks to a light color of 6000 Kelvin you won’t miss a single detail, even in sudden banks of fog."
    https://www.carlightblog.com/2016/09...-horror-story/
    Last edited by -Virgil-; 10-02-2016 at 12:15 PM.

  12. #12

    Default Re: "Whiter" headlights...CCT, CRI, SPD?

    In a paper published by the National Highway Traffic Safety Administration, the legal authority of the United States of America, makes a dozen references to whiter light. Within this paper, they speak of white light being a range of color as required by Standard 108, and they reference the appearance of light color as seen by the human eye. Even so, if one of the worlds preeminent depositories of lighting knowledge is comfortable with the term, “whiter light”, it does seem that this illustrious website should be at least as tolerant and understanding when we mere mortals discuss whiter light.

    Through out the paper the writers state:
    “HIDs are not just more white (having less yellow content and more blue content in the emitted spectrum), but the light is generated in a different manner”, and “Their robust illumination performance and whiter, almost blue, color make them easily identifiable as a new source of glare.”

    “As introduced, the halogen lamps, generally, were not intended to be more intense than non-halogen headlamps; their only distinguishing characteristic was that they were whiter in color than other headlamps in use”, and “It is possible that our eyes are not necessarily reacting to the whiter light, but to the high energy spikes that rise above a background energy achieving the white light.”, along with, “The whiter light is offered as being closer in color to natural daylight, thus the claim is that drivers see better with the same amount of emitted light.”

    And in discussing newer bulbs, “These careful changes may continue to make the bulb interchangeable with an OEM design without noticeable consequence other than whiter light.”

    If such use complicates someones life, this same paper offers this:
    “For technical issues, please contact Mr. Chris Flanigan, Office of Safety Performance Standards, NHTSA, 400 Seventh Street, SW, Washington, DC 20590. Mr. Flanigan's telephone number is (202) 366-4918 and his facsimile number is (202) 366-4329. For legal issues please contact Mr. Taylor Vinson, Office of Chief Counsel, at the same address. Mr. Vinson's telephone number is (202) 366-2992.”
    Last edited by -Virgil-; 10-02-2016 at 12:15 PM. Reason: Remove a bunch of spurious font formatting

  13. #13

    Default Re: "Whiter" headlights...CCT, CRI, SPD?

    I believe that what is at issue here is not what are the most scientifically correct, meaningful, and useful terms, but rather what terms can I/we use as 'wrappers'.

    The I/we that I speak of are not lighting professionals with thousands of hours of specialized study and training. Rather, we are interested, reflective, studious and have a modicum of experience with automotive lighting. That experience, though, is usually based upon a sample of one (in my case, that being me). We have not the wherewithal to poll many users and witness many installations in all forms of terrain, ambient light and weather to obtain a broad background. We come here for that and come in the hopes that we can express what our interests and needs are without getting beaten with technical pedantry. Automotive lighting is but a facet of our lives, it is neither our lives nor our livelihood.

    SPD is a fine tool for comparing and understanding, if you can get the information. It also helps to know what works for you, the individual. You, the individual, are a part of the average but you may be almost a standard deviation off. That would make you different than the average that you are a part of. I have stated a preference for light that has quite a yellow cast. Perhaps I have a preponderance of long-wavelength cones in my eyes; I don't know. But it raises the question, then, what should the SPD be? Would I look for a light with an SPD that has more power distributed to the longer wavelengths? In formal vision testing, how would I react to a headlight that has a flat power distribution? A curve weighted toward the shorter frequencies?

    But at the crux of the matter is, if I am interested in buying a headlight or bulb, where would I get that information? If I can't get the information, of what use is my understanding of SPD? I have never seen SPD data for any commercial forward lighting application.

    CRI is an interesting number. I think it is a bit less esoteric than SPD. Generally speaking (though not entirely) it will tell me how well the light will accurately render color. But again, where do I get that information for a given headlamp or bulb? Am I limited to rules of thumb? LED ~ 80, incandescent ~ 95? Do I need to subscribe to a library of technical journals in the hopes that someone will test the new Sylvania SuperSilverStar Racing +666 and tell me that the CRI is, um, 20? I know that the LED lighting that I have installed throughout my house has a CRI of 82. I believe that the H9s in my Forester have a CRI of 95ish, as most do. Beyond that, I know twiddly twat about what the CRI of lamps and bulbs are; there is a dearth of information. This, too, I don't find in the manufacturer's information.

    I realize that, to the lighting cognoscenti, the use of anything less than scientifically perfect terminology is grating. It's imprecise. There is fear that it will lead to misperception and the perpetuation of myth and urban legend. However, those of us who are merely interested in the subject matter (and perhaps well read and above average in comprehension) find a need for 'wrapper terminology'. Granted, that terminology is not codified and so the communication is imperfect. A man with pointed ears once said "This thing you call language though, most remarkable. You depend on it for so very much. But is any one of you really its master?"

    When I am figuratively standing around the water cooler having a conversation with someone who sure seems to be knowledgeable, I'm going to say "...anything much 'whiter' than conventional halogen bothers me.." and am going to be comfortable that it will be received as, "Yeah, I know what you're saying. Conventional halogen's CCT is comfortable, has a good CRI and the SPD works. If it works for you, it works. Shorter wavelengths in the white spectrum can be tiring, especially to an old guy like you."

    In an in depth conversation I'm more likely to talk about CCT, illumination source's position within the white boundaries, wonder about CRI and never mention SPD. I'm going to be interested in what the pattern looks like, as I have preferences on cut-off configuration and pattern shots can be telling off off-axis color crap. I'm going to be interested in bird's eye diagrams and road shots, as I have needs that relate to what I drive, how I drive, and where I drive. Less wrapper, more content.

    Tom
    Last edited by -Virgil-; 10-02-2016 at 12:15 PM. Reason: sp

  14. #14

    Default Re: "Whiter" headlights...CCT, CRI, SPD?

    Quote Originally Posted by souperdoo View Post
    SPD is a fine tool for comparing and understanding, if you can get the information.
    Generally we can't get precise SPD information for any given lamp, but that won't matter unless/until someone puts out a headlamp with unusual SPD characteristics. Without that happening, it's enough to know that the SPD of automotive HID and LED headlamps tends to be deficient in red and heavy in blue.

    But at the crux of the matter is, if I am interested in buying a headlight or bulb, where would I get that information?
    Usually we don't go shopping for headlight bulbs on the basis of their SPD, if only because we don't have a choice. Filament bulbs (including halogen) have a smooth SPD that is strongest in the reds, weakest in the blue/violet, and the line connecting the red end to the violet end of the spectrum is pretty a pretty straight slope. Some bulbs have blue coatings that tweak the spectrum a little by suppressing yellow; this is of no benefit in terms of ability to see, but it greatly benefits the maker's bottom line because it creates a platform for marketing babble ("whiter", "closer to daylight", etc).

    CRI is an interesting number. I think it is a bit less esoteric than SPD. Generally speaking (though not entirely) it will tell me how well the light will accurately render color.
    That's correct.

    But again, where do I get that information for a given headlamp or bulb? Am I limited to rules of thumb?
    Yes, and again, that's all that's needed unless/until someone puts out something unusual, like an LED headlamp with high CRI. As with SPD, we don't go shopping for a headlight bulb by CRI, because we don't have a choice. Halogen bulbs are close to 100, HIDs are mid-70s, and LEDs are high 70s to low 80s.

    This is different than shopping for lights for use in the home, office, retail store, gallery, etc -- in those cases, CRI is a selection criterion that can be specified when choosing HID, fluorescent, and LED lights.

    Do I need to subscribe to a library of technical journals in the hopes that someone will test the new Sylvania SuperSilverStar Racing +666 and tell me that the CRI is, um, 20?
    No. It's a halogen bulb, so its CRI is close to 100.

    When I am figuratively standing around the water cooler having a conversation with someone who sure seems to be knowledgeable, I'm going to say "...anything much 'whiter' than conventional halogen bothers me.."
    That's unfortunate. You'd be doing yourself and your listener a favor by saying "bluer" instead, because that's what you actually mean.
    Last edited by -Virgil-; 10-02-2016 at 12:15 PM.

  15. #15

    Default Re: "Whiter" headlights...CCT, CRI, SPD?

    Quote Originally Posted by fastgun View Post
    In a paper published by the National Highway Traffic Safety Administration, the legal authority of the United States of America, makes a dozen references to whiter light.
    Yes, it does. Note that document you're quoting from is not a "paper", as such.

    “HIDs are not just more white (having less yellow content and more blue content in the emitted spectrum)
    Improper usage remains improper no matter how many instances of it we can find. This is kind of like people referring to earthquakes as "five point six on the Richter scale" or people talking about color temperature in "degrees Kelvin" or people saying "Nukyellur" when they mean nuclear, or people saying "It's a doggy-dog world" when they mean dog-eat-dog, or people pointing to a carrot and saying "That's a stapler".

    Light that has one color cast instead of another color cast just plain is not "whiter". Words mean things, and that's not what that word means.

    “As introduced, the halogen lamps, generally, were not intended to be more intense than non-halogen headlamps; their only distinguishing characteristic was that they were whiter in color than other headlamps in use”
    That's actually not the case. The entire reason for halogen headlamp technology coming to the USA was that the maximum allowable high beam intensity was doubled from 37,500 to 75,000 candela per side of the car. Without halogen technology, it was not possible to achieve the higher intensity without unreasonably high filament wattage, and so the first halogen headlamps on US roads were the high beams in the four-round and four-rectangular systems -- remember, this was in 1978, which was still in the era when all US vehicles had either two or four round or rectangular sealed-beam headlamps. These were both more intense and brighter than the previous non-halogen high beams, so a driver would be "zapped" a lot harder by someone who failed to dim to low beam. (More detail, if you want it, is in this paper). That probably caused some of the complaints referenced in the document you found.

    A brief time later, inexpensive high/low-beam halogen sealed beams were developed. These, on low beam, are the ones the writer of that document (long retired from NHTSA, as is Taylor Vinson) refers to as having not been intended to be more intense than non-halogen headlamps. He's right as far as that statement goes: the design brief for halogen low beams was not "keep the wattage the same and give the driver more light" as had been the case in Europe almost 20 years prior. Instead, the US design brief was "keep the performance legal and reduce the wattage". For example, the type 4000 sealed beam (5.75" round, high/low beam, non-halogen) had a 60-watt low beam filament and a peak intensity of 24,000 candela. Its halogen replacement, the H5006, had a 35-watt low beam filament and a peak intensity of 19,000 candela. That's 20% less intense, but those halogen lamps provoked glare complaints. The public sometimes put those complaints in terms of "whiter" light, but what they were actually objecting to was greater glare intensity from the new halogen lamps.

    The beam pattern from many halogen sealed beams was quite a lot blurrier and "noisier" than from a non-halogen sealed beam. In manufacturing a non-halogen sealed beam, the filaments can readily be precisely focused with respect to the reflector, so the hot spot (high-intensity zone) can be maximized and optimally placed while minimizing light in the glare zone (above and to the left of the hot spot). Because there is nothing between the filaments and the reflector, stray light is minimal. With a halogen sealed beam, you're installing a "burner" (glass capsule containing filaments). You can't focus the filaments relative to the reflector, because you don't have access to the filaments -- only to the outer surfaces of the burner. So the focusing procedure necessarily changed from adjusting filaments to maximize the hot spot and minimize glare, to adjusting the burner to get the glare level under the legal maximum. Furthermore, the glass capsule itself introduces a significant amount of stray, unfocusable light because of filament reflections off the capsule walls and the glass pinch and filament support anchor bar. And while non-halogen sealed beams had filament shields that did a very complete job of blocking waste light that would cause glare and backscatter by going from the filament directly through the front lens, the vast majority of halogen sealed beams did not. They had an opaque coating on the front of the halogen burner, which does a partial job but still allows a significant amount of waste light. So all those factors together meant that the halogen sealed beams, even though they tended to put less light on the road for the driver on low beam, really were more glaring than the non-halogen sealed beams everyone was used to.

    This got worse with the 1983 introduction of replaceable-bulb headlamps in the US -- the low beam intensity cap of 5,000 candela straight ahead of the lamp, which had been in place for many years, gave manufacturers fits when making halogen sealed beams for the focus reasons just described, was deleted from the specifications for replaceable-bulb headlamps.

    So that's what was causing the bulk of the glare complaints; it wasn't that people were saying "I object to the whiter light", it's that they were saying "I object to the glare from these whiter lights". It might be a fine distinction, but it's an important one. And also important is that in this case, "whiter light" really was completely accurate. The halogen sealed beams had less of an orange-yellow color cast to the light than the non-halogen lamps, and they did not have any other color cast. So they really were whiter -- less colored. That is really very completely different from the issue at hand when that document you're quoting was written, which was HIDs versus halogens. In the tungsten/halogen case you have two lamps with very similar SPD and CRI, but the new one has less of a color cast. In the HID/halogen case you have two lamps with very different SPD and CRI, and the new one has a strong blue color cast.

    Keep in mind that when that document was written, NHTSA's position on the matter was that because all headlamps have to meet the same glare limits, there is no basis for complaint that one kind of headlamp is more glaring than another. Even before UMTRI research (corroborated four years later in this study) found that headlamp light of a given intensity with a higher blue content produces a 46% stronger subjective glare response than headlamp light of that same intensity with a lower blue content, NHTSA's position was not technically defensible, though it was an industry-friendly position. (also see an earlier UMTRI study on the matter, if you're interested).
    Last edited by -Virgil-; 10-02-2016 at 02:17 PM.

  16. #16

    Default Re: "Whiter" headlights...CCT, CRI, SPD?

    There is another aspect to this that I think may be being overlooked and it may or may not apply in this case, and that is the meaning of words is not immutable.

    To make this simple(since I'm typing on my phone) words were given a meaning by someone, but as often times is the case, certain people use it as a slang word with a totally different meaning than the word originally had. Eventually the slang term is all everyone knows and the original meaning gets lost.

    In the case with the term "whiter light" if 90%(an arbitrary percentage) of the people who use the words everyday including the government, major corporations, and a host of other people, are using it to mean "bluer light", and that's all most people understand it to mean, wouldnt it eventually get to the point wherein it would be pointless to insist that the word means something that's almost obsolete now?
    Last edited by Magio; 10-02-2016 at 02:24 PM.

  17. #17

    Default Re: "Whiter" headlights...CCT, CRI, SPD?

    Virgil,

    Thank for the discourse and for the links.

    I note one thing with "BLUE CONTENT OF LED HEADLAMPSAND DISCOMFORT GLARE" that seems odd. If you have insight, perhaps you could comment.

    In this experiment the headlamps were arrayed directly in front of the subjects at a distance of 40 meters, with the LED lamps in the central positions and the others to the right and left of center. The subjects were to look at a point situated below the lamps. The lamps were never re-positioned during the experiment.

    It would seem that a more realistic experimental set up would be to have the lamps each positioned ~4 meters to the left of the subjects' vehicle center-line, out 40 meters, with the subjects focusing on a spot directly in front of them at a distance of 40 meters. This set-up would more accurately reflect the on-road positioning and more accurately present the glare signature of the lamps. I recognize that it is color they are testing, not lamps, but still seems an obvious point to question.

    I continue to read.

    Tom

  18. #18

    Default Re: "Whiter" headlights...CCT, CRI, SPD?

    Quote Originally Posted by Magio View Post
    There is another aspect to this that I think may be being overlooked and it may or may not apply in this case, and that is the meaning of words is not immutable.
    That's a never-ending argument between linguistic prescription and linguistic description. Entire academic careers have been built on staking positions in that argument. We're not going to solve it here. :-)

    if 90% of the people who use the words everyday including the government, major corporations, and a host of other people, are using it to mean "bluer light", and that's all most people understand it to mean, wouldnt it eventually get to the point wherein it would be pointless to insist that the word means something that's almost obsolete now?
    This question has no "right" answer because neither answer is realistic. On one hand, words have to have agreed (i.e., standardized) meanings for language to work. On the other hand, languages die if they stop evolving. There is no clear point anywhere along the continuum that is the "right" balance between the two positions; everyone has to make up their* own mind where to draw the line. "Nukyellur" is correct because a lot of people say it? No, it's popular and still wrong. It bears no resemblance to the actual word (nucular). "Doggy-dog world" is correct because a lot of people say it? No, it's meaningless even though it sounds vaguely like the actual saying (dog-eat-dog). "Whiter actually means bluer"? No, it's not the case any more than "stapler actually means carrot"...no matter how many people believe it. That's my opinion; you may choose, if you want, to give up and let people wallow in ignorance because you think it's pointless to try to educate them.

    *That right there is a perfect example: prescriptionists would argue that "everyone has to make up their own mind" is ungrammatical, because "everyone" is singular and "their" is plural. Descriptionists would counter that the supposedly correct construction, "everyone has to make up his own mind" is sexist, and other fixes for it like "everyone has to make up his or her own mind" are awkward, so "their" has been adopted as a single non-sexist word.

  19. #19

    Default Re: "Whiter" headlamps...CCT, CRI, SPD?

    In "VISUAL EFFECTS OF BLUE-TINTEDTUNGSTEN-HALOGEN HEADLAMPBULBS" the set-up is simulated headlights 3.66m to the left. Makes sense.

    Tom

  20. #20

    Default Re: "Whiter" headlights...CCT, CRI, SPD?

    Quote Originally Posted by souperdoo View Post
    In this experiment the headlamps were arrayed directly in front of the subjects at a distance of 40 meters, with the LED lamps in the central positions and the others to the right and left of center. The subjects were to look at a point situated below the lamps.
    It would seem that a more realistic experimental set up would be to have the lamps each positioned ~4 meters to the left of the subjects' vehicle center-line, out 40 meters, with the subjects focusing on a spot directly in front of them at a distance of 40 meters. This set-up would more accurately reflect the on-road positioning
    The point of the experiment was not to simulate an on-road position, it was to examine discomfort glare reactions to different kinds of light. Given what they were studying, there is nothing incorrect about how they set up the experiment.

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