Talk:Selective yellow
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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)
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- 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)
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- I think so... DanielCristofani 14:37, 9 December 2005 (UTC)
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- 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:
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| Selective yellow (desaturated approximation) | ||
|---|---|---|
| — Color coordinates — | ||
| Hex triplet | #FFFF00 | |
| RGBa | (r, g, b) | (255, 255, 0) |
| HSV | (h, s, v) | (43°, 255%, 255%) |
| a: 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)
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- 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?
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- 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)
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- 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.
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- Selective Yellow driving lamps are generally legal wherever selective yellow headlamps are or were permitted. Offhand, that means Japan, France, The Netherlands, Switzerland, etc.
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- 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)
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| Selective yellow | ||
|---|---|---|
| — Color coordinates — | ||
| Hex triplet | #E3FF89 | |
| RGBa | (r, g, b) | (243, 255, 137) |
| HSV | (h, s, v) | (?°, ?%, ?%) |
| a: Normalized to [0–255] (byte) | ||
| Amber | ||
|---|---|---|
| — Color coordinates — | ||
| Hex triplet | #FFB169 | |
| RGBa | (r, g, b) | (255, 177, 105) |
| HSV | (h, s, v) | (?°, ?%, ?%) |
| a: Normalized to [0–255] (byte) | ||
| White | ||
|---|---|---|
| — Color coordinates — | ||
| Hex triplet | #FFFFFF | |
| RGBa | (r, g, b) | (255, 255, 255) |
| HSV | (h, s, v) | (?°, ?%, ?%) |
| a: Normalized to [0–255] (byte) | ||
| Red | ||
|---|---|---|
| — Color coordinates — | ||
| Hex triplet | #FF3337 | |
| RGBa | (r, g, b) | (255, 51, 55) |
| HSV | (h, s, v) | (?°, ?%, ?%) |
| a: 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?
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- Eeek! Your new selective yellow is fairly close in hue, but is far, far too desaturated. Your amber is salmon pink.
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- 3200K would indeed be a reasonable white point upon which to stake calculations, since we have to pick one and go with it.
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- Of tangential interest, I'm told that single-emitter LEDs are unable to produce selective-yellow light.
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- 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)
[edit] 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)
