Talk:Selective yellow

Colourbox presentation

It's MESSY having the a color box showing a color that is not the color the article is about. My suggestion is that someone familiar with color theory should figure out an RGB color that LOOKS LIKE selective yellow to the average human eye, make the box THAT color, and give it some name like "visual approximation of selective yellow" or something.

I tend to agree. But the Color WikiProject has made a rod for its own back by demanding absolute colour coordinates for all its colours — but any coordinates we give would be inherently wrong. But as long as the text explains that the coordinates given aren't valid, I suppose it'd do.

I'm not much of an expert in colour theory. I can give you the sRGB coordinates for the centroid of the proper colour definition (with B being negative). But I'm not sure what the best way to map that into the sRGB gamut is, to keep the hue as perceptually close as possible. At a guess, drawing a straight line between D65 white and the centroid in the CIE XYZ or CIELAB space, and choosing the intersection with the edge of the sRGB gamut?

Although from what I recall of my fiddling when creating the article, that choice would still look quite orangey on many monitors (certainly on my LCD monitors). --KJBracey 09:03, 9 December 2005 (UTC)

Okay, I've created a new approximation by that method, as various sources suggest it's an appropriate technique. Still quite orangey, but definitely more yellow. On my monitor, I'd say it looks like a not bad hue approximation to the yellow lamps I've seen (although it's definitely not pure enough). --KJBracey 10:46, 9 December 2005 (UTC)

Excellent.

Now, I could do the same for Amber (color), as at the moment the swatch there is actually more yellow than Selective yellow. I did put the UNECE definition on there, but I didn't touch the swatch. I'll compute the same approximation for the UNECE definition, and propose it as new swatch. As after all, isn't one of the main times people use "amber" as a colour in traffic lighting? --KJBracey 10:55, 9 December 2005 (UTC)

I think so... DanielCristofani 14:37, 9 December 2005 (UTC)

Colour box still looks way too orange on all six monitors I've viewed it with. It's a little difficult to nail down a single visual approximation of selective yellow, because it is a colour range, not one specific colour. That said, a pure centric yellow (in CMYK space, 0% C, 0%M, 100%Y, 0&K) is a very close visual approximation of the light colour under discussion. Here are the calculated values for such an approximation:

Selective yellow (desaturated approximation)
Color coordinates
Hex triplet	#FFFF00
sRGBB (r, g, b)	(255, 255, 0)
HSV (h, s, v)	(60°, 100%, 100%)
CIELChuv (L, C, h)	(97, 107, 86°)
Source	[Unsourced]
B: Normalized to [0–255] (byte)

I think it is more appropriate to approximate the colour of the light (as it would appear when projected on e.g. a white surface) rather than trying to describe the colour of whatever filter is used to attain that colour (e.g. headlamp lens or filter balloon, reflector coating, etc.), for the appearance of such optical elements is very widely variable depending on the filtration technique used and the filter's placement within the optical system.

I have also gone through and updated/corrected the discussion of presently-pending ECE proposals regarding selective yellow light, and of the primary reason for its use (there is no Rayleigh Scattering of blue light with water droplets in the size range encountered in common fog, rain and snow—the primary glare and scatter locus of blue light is in the human visual system.) Scheinwerfermann 22:56, 16 December 2005 (EST)

The UNECE colour specifications are for the final output of the light, not for the filters.

Indeed not much filtering is needed, as the 2900K tungsten light source is pretty damned yellow to start with. See white point. The pure sRGB yellow you've shown there is far too lemony/green, but on the positive side, it's brighter. The colour mapping problem we have is that we cannot get close to the necessary hue on an sRGB display without surrendering a lot of brightness - the page background is near full intensity, and we can only go yellow by removing blue. My approximation tried to get the colour right (being a colour article) at the expense of brightness, even though the visual effect is odd - we're on a display with a very blue white point (D65), and on top of that, the encyclopedia's default background is a pale blue relative to that, and if your using Windows XP its default window interface is a rich blue. Any accurate colour you put on that background will look perceptually orangey. Doubly so when the colour swatch is necessarily darker than the background - totally unnatural. But this is an encyclopedia, so surely we should give technically correct information?

I agree we want some way of showing the colour in context in a natural setting to give a less technical reader a better idea, and I think your photographs serve that purpose very well. By the way, are selective yellow driving lamps legal anywhere? --KJBracey 10:48, 17 December 2005 (UTC)

Certainly the UNECE colour specs are for the final output and not the filter, but the colour box you've posted does not present a visually accurate representation of either a lighting device that produces selective yellow light, or of that light itself. I do not use XP or any other blue-background setup. The difficulty we're having here isn't so much that we can only go yellow by removing blue, for that's exactly how selective yellow light is created. The problem we're having is fundamental, as you mention, to the limitations of sRGB. I'm not sure there is a satisfactory solution to this one. Anything we show as a colour box is just not going to be right, so technically correct information isn't an option, and we're just debating subjective preferences for how to work around that. My position is based on the fundamental difference between amber (now yellow) and selective yellow, as defined by ECE (and by SAE, for that matter): There's very much less red/orange allowed in selective yellow under both colour regulations. I think that ought to be the main thrust of the point we're trying to convey.

Selective Yellow driving lamps are generally legal wherever selective yellow headlamps are or were permitted. Offhand, that means Japan, France, The Netherlands, Switzerland, etc.

Finally, your comment that my proposed colour box is too lemony/green seems based on mental comparison to the output from lighting devices equipped with filament lamps. There exist (believe it or don't!) automotive HID D2S and D2R lamps ("bulbs") made by Philips that produce selective yellow light in compliance with the ECE definition of that colour. These are marketed primarily in Japan. I have a few here on the test bench, and they produce a distinct and strong lemon-yellow light output. Contrary to what seems logical, the output is not green, except at initial startup before the halides vapourise. --Scheinwerfermann 13:37, 17 December 2005 (EST)

Selective yellow
Color coordinates
Hex triplet	#E3FF89
sRGBB (r, g, b)	(227, 255, 137)
HSV (h, s, v)	(74°, 46%, 100%)
CIELChuv (L, C, h)	(96, 75, 99°)
Source	[Unsourced]
B: Normalized to [0–255] (byte)

Amber
Color coordinates
Hex triplet	#FFB169
sRGBB (r, g, b)	(255, 177, 105)
HSV (h, s, v)	(29°, 59%, 100%)
CIELChuv (L, C, h)	(78, 81, 42°)
Source	[Unsourced]
B: Normalized to [0–255] (byte)

White
Color coordinates
Hex triplet	#FFFFFF
sRGBB (r, g, b)	(255, 255, 255)
HSV (h, s, v)	(0°, 0%, 100%)
CIELChuv (L, C, h)	(100, 0, 0°)
Source	[Unsourced]
B: Normalized to [0–255] (byte)

Red
Color coordinates
Hex triplet	#FF3337
sRGBB (r, g, b)	(255, 51, 55)
HSV (h, s, v)	(359°, 80%, 100%)
CIELChuv (L, C, h)	(56, 159, 12°)
Source	[Unsourced]
B: Normalized to [0–255] (byte)

Okay, the problem isn't that we have to remove blue, the problem is that we're working in the presence of lots of other illuminants, with a blueish white point (ever seen a room illuminated just by a TV from outside a house - very blue!), rather than in the dark. So we look yellow, just as "white" headlamps do in daylight.

I think the main reason I feel quite strongly about the way I produced the swatches is because the Color WikiProject insists on having those RGB, CMYK etc values on their pages. Now, for most of their colour articles, any numerical values are basically nonsensical, except for a few cases where the "colour" is an HTML specified one or something. But in this case, there is an official definition of the colour, so the RGB values should be calculated on some sort of rational basis.

Now, the way I've calculated it at present, I'm pretty confident that if you took a monitor calibrated to sRGB, filled the screen with my RGB value, stuck it in a dark room and compared it to a piece of white paper illuminated by a selective yellow lamp, it would be the optimal match. Or, looking at it another way, if you wanted to strap an LCD monitor to the front of your car, and use it as a foglamp, those RGB coordinates would give you the best chance of getting away with it. It's colorimetrically optimal, if visually poor. I'm not in a position to do that test though. :(

Given that we're working with a D65 white point here, maybe we should attempt to compensate. Using this color calculator, selecting A as the reference white and requesting Bradford adaptation (its default), I get the swatches here. Selective yellow is using the same colour as before, white is illuminant A (ie incandescent tungsten, which is pretty much central within UNECE's white definition), amber is somewhere in the amber definition, likewise red. What do you say to these? I'd rather do it with the white point at something like 3200K, which I believe is more representative of a halogen lamp, mind.

I'm fascinated that people are actually producing yellow HIDs. Aftermarket? As headlamps or fogs?

Eeek! Your new selective yellow is fairly close in hue, but is far, far too desaturated. Your amber is salmon pink.

3200K would indeed be a reasonable white point upon which to stake calculations, since we have to pick one and go with it.

Of tangential interest, I'm told that single-emitter LEDs are unable to produce selective-yellow light.

Yeah, I was fascinated to find yellow HIDs from a major/reputable manufacturer. See Here (translated Here) for the Philips version. They're marketing it as "3000K", which of course is complete nonsense (light not of a colour found on the blackbody curve not having any applicable Kelvin temperature), and the picture on the page is of standard ordinary bulbs. Here is an auction for a pair of them; you can see not only the burner itself (which has a multilayer dichroic coating to produce the selective yellow light) but also a few pictures of the lamps in use and the resultant beams. The photos are a good match for what I have observed with these burners in lamps on my test bench. They are sold for aftermarket use in Japan and other Asian countries, where vehicle-in-use regulations are extremely lax regarding headlamp modifications.

--Scheinwerfermann 15:03, 18 December 2005 (EST)

Yellow headlights still allowed in Europe / the EU? They are in The Netherlands.

Although there is 'talk' on this issue, the actual article still suggests road-use of yellow headlights not being allowed in Europe, or under EU-regulations. Dutch legislation, as published by the official government-body 'RDW', however, clearly states road-use of yellow headlights being allowed, for both cars and motorcycles, as well as lorries and buses. I've been using conventional non-halogen yellow bilux/duplo-bulbs in the headlights of my old Citroën for years, and it passes it's mandatory yearly safety-check-up every time, with fore-mentioned bulbs in place. Would anybody be able to edit the article towards stating more clearly what is actually allowed, regarding the use of yellow headlights, in all the countries effected by UNECE-regulations?

Reginald P. 19:12, 15 February 2007 (UTC)

The UNECE rules a basis upon which national and trade rules are built. As I understand it, it works like this...

The Netherlands is free to permit whatever it likes on cars. However, if it were to manufacture cars with yellow headlights, then those cars would not obtain UNECE type approval. And as such, other countries' legislation may then use that as a basis to refuse their import and registration.

EU membership then takes things a step further - the EU as a whole is a signatory to the UNECE regulations, and its own EU-wide regulations are based upon them. If a EU-manufactured car meets EU approvals (which are basically the same as UNECE approval), then an EU member is required to allow its free import. Thus the Netherlands cannot require yellow headlights, as that would be preventing manufacturers from importing type-approved white-headlight cars — a restriction on trade.

Someone can now correct me. An explanation of all this is really needed in the World Forum for Harmonization of Vehicle Regulations article. --KJBracey 16:09, 26 February 2007 (UTC)

Link

Please tell me what is in that link that cannot be included in the article. --Legionarius (talk) 19:48, 31 December 2007 (UTC) And while we are discussing this link, could you please detail who is the author or the references he uses in his article? It looks like just a site to sell lighting products.--Legionarius (talk) 19:59, 31 December 2007 (UTC)

You're right, per WP:EL the link didn't belong. I re-removed it. --Scheinwerfermann (talk) 20:04, 31 December 2007 (UTC)

Much better as a reference. Thanks.--Legionarius (talk) 20:08, 31 December 2007 (UTC)

Disadvantages of selective yellow headlamps

Reading the article now you have to wonder why every car isn't still equipped with selective yellow (especially as I'm French and lived through the change from yellow to white as a kid, I even remember my dad removing the yellow filters on our Peugeot 405 station wagon in the early 90's) since it seems to be a better color than white. So, why was it banned on new cars ? Aesma (talk) 14:29, 27 July 2012 (UTC)

You're right, this is definitely an incomplete article. It's a very good start; it presents the definition, the putative raisons d'être, the history, some good photos and references to some apparently reliable sources, but no discussion of why it was not widely adopted outside the Francosphere. This will be somewhat tricky to write up in an encyclopædic manner, because unfortunately some difficult-to-support cultural factors came into play: whatever other reasons there were -- and there were some -- Germany spent many years bitterly fighting to get rid of selective yellow headlamps solely because the idea was French. For anyone who is educated and/or experienced in the long history of reciprocal German/French cultural rejection, this is easy to believe and understand. Unfortunately, it is very difficult to support to the standards required by this project. Nevertheless, at least some aspects of the supercession of yellow headlamps by white ones ought to be appropriately supportable without much difficulty.

One point that merits some research: I am under the impression that yellow headlamps were not banned on new cars; when France dropped the requirement for yellow headlamps in 1993, they did not adopt a requirement for white ones; the change was that new cars with white headlamps could be registered in France and old cars could have white headlamps instead of the yellow ones they came with. One still occasionally sees a car with yellow headlamps in France, and my understanding is that even a vehicle newer than 1993 may be equipped with yellow headlamps as long as they are of a type that complies with the applicable regulations. However, I do not have a direct source available to support this belief. The French Wikipedia article on headlamps says:

Lors de la guerre 1939-1945, la France a adopté les phares jaunes (…) avoir des 
phares blancs sur une voiture immatriculée en France avant janvier 1993 était
passible d'une amende). Ce système fut abandonné, au profit des phares blancs
en janvier 1993 et ainsi d'une meilleure harmonisation européenne, mais il reste 
légal pour tous les véhicules.

which, for our non-Francophone participants, means during WWII, France adopted yellow headlamps (…) having white headlamps on a vehicle registered in France before January 1993 was a traffic infraction. This system was abandoned in favour of white headlamps, for better European harmonisation, but [yellow headlamps] remain legal for any vehicle. However, there is no citation provided for this assertion. It would be good if someone could have a look at the French national requirements and see what they have to say on the matter. Are you in a position to do so?—Scheinwerfermann ^T·_C23:16, 27 July 2012 (UTC)

Update Never mind, I found the applicable French regulation, amended as of 2008 and currently in force, which reads (in French, of course) […]tout véhicule à moteur doit être muni à l'avant de deux ou de quatre feux de route émettant vers l'avant une lumière jaune ou blanche […] tout véhicule à moteur doit être muni à l'avant de deux feux de croisement, émettant vers l'avant une lumière jaune ou blanche. This translates as "Each motor vehicle must be equipped at the front with two or four high beams emitting white or yellow light in a forward direction (…) each motor vehicle must be equipped at the front with two low beams emitting white or yellow light in a forward direction". So yellow headlamps are still legal in France regardless of the production or registration date of the vehicle. That will be good information to include in the article. —Scheinwerfermann ^T·_C01:23, 28 July 2012 (UTC)

Thanks for your answers. I didn't mean that old cars had to change color, it's true that you sometimes still see old cars with yellow and as I like old cars I even think that for classics they should stay that way (now I guess if it's a BMW, switching to white makes sense reading your answer). Now, putting yellow lamps on a new car, I don't know. Sure the law says it's legal, but that may mean that a manufacturer can certify a new car with yellow lamps, not that you can change the color yourself. In France pretty much any modification renders a car illegal unless you pay for a new certification, a costly process, the same one you need to do if you import a car that is not sold locally. In practice I doubt you would get into trouble, and even insurance companies would probably turn a blind eye, but you never know. More importantly it would be interesting to find sources for the process that led to the European law, the motivations of each party. I can say that white was instantly popular, which may not have been the case if we had known it was a "German diktat". The novelty of white lamps made cars with yellow ones dated overnight. Aesma (talk) 13:58, 28 July 2012 (UTC)

The direct records of the relevant standards-and-rules body (GRE) are generally accessible, but only back to 2000 online. I will make some enquiries and see if I can get access to the earlier records. Having attended meetings of that body for a good number of years, I recall a great deal of unvarnished animosity towards the yellow lights on the part of the Germans, phrased in terms denigrating to the French. These remarks, of course, were generally not made on the record—they were made over coffee or lunch or dinner when the real work gets done at such meetings.

This 1976 study will serve as a good reliable source for expansion of the article with regard to colour of light emitted by headlamps specifically (vs. front fog lamps, a yellow-advantage of which is already well supported in the article). Page 12 gives a good itemised list of the factors at work, concluding with "In view of all the factors for perception, which might influence motorised road traffic, the colour of light is unimportant. Yellow and white light are equivalent." That appears (by reference to the rest of the literature) to be theoretically sound, though the study notes (p 16) that a reliable 1954 study found seeing distances were 2-3 metres longer with yellow light. That study would be worth digging up.

Note the 1976 study does a good job of comparing visual acuity and glare with yellow and white headlamps (theoretically), but does not quite fully answer the question of whether yellow and white headlamps give equal or different safety performance (practically). To do such research would have required analysis of crash data for cars equipped with yellow vs. white headlamps. Perhaps the French national road safety people looked at that after the changeover; I don't know. If they did not do so at the time, then that study will never be done because there no longer exists a sufficient population of cars with yellow headlamps. Moreover, as the linked study states there is a filtration loss of (at most) 15% involved in producing yellow light. Does it matter? The study says probably not, and that is probably correct; it is well documented in the headlighting literature that changing the intensity by less than 15-20% has no effect on driver visual performance. But as far as I know there was no study comparing yellow and white headlamps of equal intensity (attained by operating the yellow lamps at higher than rated voltage to bring its photometric intensity up to that of the otherwise-identical white lamp, or by applying a neutral density filter over the white lamp to bring its photometric intensity down to that of the otherwise-identical yellow lamp). It is worth considering that most of the cars in the linked study had very low output 45w tungsten headlamps (with R2 bulbs); these must be considered quite inadequate on a simple mathematical basis for real-world road speeds no matter their colour; a study comparing the safety performance of yellow vs. white Xenon or high-output halogen headlamps might reach a different conclusion. It is also interesting that the 1976 study's finding that more-yellow/less-blue light produces less discomfort glare for any given intensity (see p. 48 near bottom of page) is reinforced by earlier studies (this one) and later studies (this one). Those together with the 1976 study does get us a good way towards a strong basis for some new paragraphs in this article. I will work on it as time allows; I'm sure others will as well.

As for the French legality situation: my understanding is that a type-approved part installed in a type-approved manner does not trigger the need to go through the controle technique again. So the vehicle owner who replaces his type-approved white headlight bulbs by type-approved yellow ones does not invalidate his roadworthiness certificate. That's how it works in Germany and the other European countries whose protocols I am familiar with; my familiarity with the French system is less intimate, though by anecdote I believe I am correct on this point. —Scheinwerfermann ^T·_C22:02, 28 July 2012 (UTC)

More

Have dug up some more useful sources and links. First off, take a look at page 81 of this French National Assembly record. §36597 has a Mr. Pierre Montastruc asking about regulatory harmonisation of vehicle lighting within the European Economic Community in February 1988. He says, "France is the only country in the European Community that uses yellow headlamps. White headlamps increase visibility for drivers and allows in particular for motorcycles to better be seen. They do not cause more glare than yellow headlights when they are aimed correctly. Are there plans to harmonise (French) vehicle lighting regulations with those of our European partners?". The response comes back "The choice and the retention of selective yellow for vehicle headlamps in France is guided by reasons of roadway safety. Experiments conducted in laboratories have shown that the selective yellow lighting produces less glare than white light does, at equal levels of illumination, for observers in conditions of glare corresponding to configurations usually encountered on the road. Furthermore, selective yellow light does not give rise to the annoying phenomenon of diffraction in rain or fog. This latter feature has also led to an almost universal use of yellow light in fog conditions for roadway and airport lighting. Moreover, the minimal filtration loss involved in using yellow rather than white, about 15%, is not the determining factor (in headlamp performance); Other parameters have a bigger effect on the real illumination; a 10% variation in supply voltage for example can vary the emitted light flux by 30%, the state of cleanliness of the headlamps can cut headlamp output in half, and a headlamp with a tungsten bulb produces 60% less light than a headlamp with a halogen bulb. Harmonisation within the EEC is accomplished since 1976 by a directive leaving the choice of headlamp colour to member states as long as all Community requirements for the approval of vehicles are met."

So that was the French government position as of 1988. Given the time scale on which pan-European harmonisation agreements are agreed and put into force, that would have been the timeframe during which the discussions were taking place in earnest in GRE and EC meetings. I suspect but cannot (yet) document that this remained the French government position right up through the end of the yellow-headlamp mandate, but given the voting structure of GRE and EC, France would quite easily have been outvoted by white-headlamp countries and not helped by any abstentions.

I did discover something very interesting about the Principality of Monaco. Take a look here at the top line. This is the road regulatory code for Monaco last updated in 2008. I can find no evidence of any newer revision, corrigendum, addendum, or amendment. Now take a look at the high beam headlamp requirement and the low beam headlamp requirement. Notice anything missing…like an allowance for white light, for example? At least on the books, it seems Monaco still requires headlamps to emit yellow light. —Scheinwerfermann ^T·_C21:00, 29 July 2012 (UTC)

Article that supports yellow

This article(http://www.dadrl.org.uk/health.html) states : "Blue and violet light has high energy and high phototoxicity causing temporal summations, increased glare, straylight, reduced contrast vision and Chromatic Aberration. Within the eye, there are no blue cones in the central retinal area, blue rays focus in vitreous body therefore blue light does not improve central vision. A Yellow Filter (420 - 450 nm cut off headlights, streetlights etc.) might improve contrast vision, reduce glare and straylight."

This info could be added to improve this page.

Red banner1917 (talk) 03:38, 14 February 2014 (UTC)