I'm not aware of any country where they're legal. To some extent automotive lighting and signalling regulations are normalized on an international basis and you can almost certainly find a phrase similar to "all forward facing lights will be only of a white of amber color" in your countries lighting regulations.
Never mind the local cops will pull you over for yellow lights thus forcing yo uto spend a day in court having the judge read the regulation to the officer.
Nor does it help to show the officer at the time the relevant portion of the highway traffic act kept in the glovebox.
I took off the yellow capsules because of this which was a real shame, they worked SO well in nasty weather (most of the time here).
They are. They improve seeing range in curves and turns.
*good headlamps* are a real plus. There are good and bad HID and halogen lamps; a well-implemented lamp of either type is better than a poorly-implemented lamp of either type. Given equally good implementation, HID is preferable.
They still do offer these, known as "BiXenon" lamps. They don't work quite as you describe. Rather, there is a solenoid that moves the cutoff shield out of the light path within the BiXenon projector when high beam is selected. NB there is no filament involved in a Xenon headlamp.
Yes, nominally, but as with all aftermarket HID "retrofits" that involve HID bulbs adaptively based to fit in halogen headlamps, installing them is dangerous, illegal, counterproductive and collossally dumb. See
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Glare can also be a concern with higher-power bulb retrofits, though most all current and recent BMWs have good enough optics with well-focused low beams such that the use of e.g. Osram's 65w H7 bulb presents no problems and gives a large increase in seeing light.
Correct. ALL of them put out significantly less light than halogen bulbs with colorless clear glass. Properly-fed halogen bulbs are not "yellowish", that is marketeering crapola. The CRI (Color Rendering Index) of a properly-fed halogen bulb is between 99 and 100. That is the one and only colorimetric measurement that meaningfully influences visual performance in undisturbed environments (clear weather).
No, they can't. In the entire civilized world except for Japan, the only legally-approved HID light sources for car headlamps produce light with CCT of 4100k to 4800k.
Nope. There is nothing at all "closer to natural daylight" about the light from automotive HIDs; this is more marketeering crapola -- it is one of the many ways CCT ("Kelvin ratings") is hackneyed and misused in order to mislead the consumer. The CRI of the best automotive HIDs is between 72 and 74. The CRI of a properly-fed tungsten-halogen lamp is over 99. 100 is perfect. On a _practical_ level, this does not materially affect seeing performance under automotive HID light relative to TH light, but we do need to dispense with this "closer to daylight" noise.
Present automotive HIDs are contraindicated for fog lamp service, by dint of their SPD. There is a selective-yellow HID product from Philips, sold only in the Asian markets, that could be used to make extremely effective fog lamps.
Common mistake. The best present LED headlamps give performance nearly equal to the low-end HID systems, with **double** the power consumption of an HID system and triple the cost. The power consumption and cost will decrease with time, but it is an error to conflate the characteristics of high-power illumination LEDs with those of low-power signalling LEDs (e.g. the little green, red and blue indicators on your electronic equipment, dashboard, etc.). Too, the system power is increased by the necessary forced-air ventilation. Remember, LEDs produce significant heat on a per-lumen basis, and instead of being cast forward with the light beam, this heat is cast rearward at the junction. The heat must be exhausted from the rear, else overheat the junction, dropping light output significantly and threatening the structural integrity of the lamp housing. At the same time, heat must be supplied to the lens of an LED headlamp for melting snow, ice and condensation fog. This usually entails electric heating, which further ups the system power consumption.
Not likely. Over 75% of the new-vehicle fleet in the first world are still factory equipped with tungsten-halogen headlamps, and while HID and LED headlamps will gradually increase their market share, they are unlikely to comprise a majority of headlamps on the road in the foreseeable future.
Wrong. There is no Rayleigh Scattering of vehicle lamp light in roadway fog. Rayleigh Scattering (the effect that makes the sky blue) occurs only when the water droplets are smaller than the light wavelengths, and such is not the case (not by several orders of magnitude) in roadway fog. The advantage of yellow light in rain/fog/snow has to do with the human visual system, which has a very tough time processing blue light.
Despite this fact, "fog lamps are yellow" is wrong. Fog lamps are permitted to be white, selective yellow, or any color in between.
That's because of what Richard said: The automotive HID burner must be hammered VERY hard to reach its full intensity as quickly as it does, and that length of time is still around 60 seconds. The Xenon present in automotive HIDs is there so that they will produce light immediately upon switch-on, which is a legal requirement.
True, but it's important to remember that this is a *light source* efficiency advantage. It does not necessarily translate to a *headlamp* efficiency advantage. It's still down to the optical engineers, stylists and beancounters (not always in that order!) to determine how efficient the lamps will be. As mentioned in a previous post, there are good and bad HID and halogen headlamps. A good one of either type is preferable to a bad one of either type.
Legal regulations worldwide call for instant-on low and high beams (to greatly simplify the requirements, which are rather more complex).
Automotive HIDs take about 60 seconds to attain full intensity.
They are available for both LHD and RHD applications.
Not really...their performance is pretty similar to the good HID systems. Here is the isoscan of the Cibie CSR low beam Richard has been talking about:
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All the performance aspects of this beam (total flux, beam width, hot spot intensity and placement, etc.) are very similar to the good HID systems. This illustrates my point in an earlier post about the difference between light source efficiency (HID has an undispluted advantage) and overall system efficiency (totally dependent on optical engineering). Note also, the plotted low beam is very clearly for RH-traffic (LH-drive) usage.
For your perusal, the matching high beam is here:
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There are actually high spikes in the blue and near-violet of the SPD of standard-production 4100k-4300k automotive HIDs.
See the above two isoplots. There are other halogen headlamps besides these that perform similarly. Some of them even come on current and recent BMWs!
That is not necessarily the case. Remember how much you liked your yellow headlamps in bad weather, before you took them out of the car? Well, it doesn't matter where such filtration is applied (at the bulb, at the lens, at the windshield, at the driver's eyes), the effect is the same.
For any given intensity, the higher the blue content of the SPD, the greater the discomfort glare -- *WITHOUT* any significant corresponding increase in seeing performance. In the case of automotive headlamps, HID vs. halogen, the discomfort glare ratio with intensity held fixed has been found to approximate 1.46 (i.e., for any given intensity level, the HID headlamp produces 46% more discomfort glare than the halogen headlamp). There has been some discussion of using this effect in inverse fashion to optimize the effectiveness of emergent LED headlamps (i.e., tweak their SPD to contain less blue, permitting higher actual intensities without increased discomfort glare), but it has been drowned out by marketeers who demand that each new generation of headlamps be bluer and bluer and ever bluer because that's what they're geared up to sell.
Just as the population at large is split roughly down the middle into glare-sensitive and glare-nonsensitive individuals, so too is it split roughly down the middle into blue-sensitive and blue-nonsensitive individuals (not the same 50/50 split; i.e., there are individuals who are glare-sensitive, blue-sensitive, both and neither). The obvious upshot is that any given HID headlamp will strike some people as more glaring (and some people as MUCH more glaring) than it will strike others.
Me, I happen to be somewhat blue-sensitive, so cutting the blue out of the light reaching my eyes at night is beneficial. Most commercial glasses sold for the purpose are grossly improper for the task; they have amber or orange or honey-brown lenses that block much too much useful light. You want to cut ONLY the blue. There are all kinds of fancy ads and competing claims for Blu-Blockers, Serengettis, etc. Most of it is BS. Your eye does not know whose name is on your lenses. Your eye also does not know how any given spectral gamut is achieved. The chief trait of an effective set of night-driving glasses is that they strongly attenuate the blue wavelengths so they don't reach your eye. When you look at a white light through this type of lens, the light will appear yellow (not orange, not amber, not brown). Interestingly, the human visual system -- with all its foibles -- does an excellent job of color correction; even when wearing glasses such as these it is not difficult to discern yellow from white road lines, for instance.
While cutting the blue and violet out of the spectrum has been shown to give some contrast-enhancement and glare-reduction effects during nighttime tasks under mesopic conditions (e.g., driving at night), it's very easy to overdo it, at which point the safety benefits of the reduced glare and enhanced contrast are overbalanced by the safety hazard caused by the absolute reduction in light reaching your eyes. IOW, it doesn't matter if a pedestrian's red shirt looks redder if you don't see him in the first place!
To help avoid an overly large absolute reduction in light, the lenses should be more towards selective yellow, and should NOT appear notably brown, orange and/or amber (which would indicate excessive attenuation of greens and yellows, which are of prime importance for human vision while driving at night). If you notice me repeating myself on this point, it's because it's so important.
Me, I had my night-driving spectacles made to my own specifications. An outfit known as "Calichrome" makes the correct-hue yellow dye. I picked a large, sturdy, inexpensive plastic frameset by Rodenstock(!), so as to handle as much of my peripheral vision as possible. Since I'm nearsighted, and nearsightedness tends to increase with fatigue *and* with dark (both of which conditions tend to exist at night), I had the lenses ground 1/4 diopter stronger than my normal glasses and my sunglasses. The lenses were then put through the Calichrome dye process to the correct-depth selective-yellow tint. I love them; they're perfect.
Your franchised "one hour glasses" type place probably won't know what the hell you're talking about and won't grind lenses to any but the prescription you hand them (those glasses-in-a-hurry places can't be relied on to adhere strictly to a prescription anyway...) so you'll have to patronize a good, competent independent optician. I had my current set made in Michigan when I lived there.
An excellent guide for the hue and tint is a "K2" type camera lens filter, available at any photo supply store.
DS
PS, remember too, the HID light source produces roughly 3x the light flux of the filament light source. This can be used by engineers for good (keep the optics the same size, increase total beam flux) or by stylists for evil (reduce the optics' size, keep beam flux "legally high"). When optical size is reduced, surface luminance increases, which creates a more glaring visual impression ("signal image"). And that's assuming quality optics; poor optics are another whole source of glare.
No, they wouldn't be particularly advantageous for high beams.
There are no selective yellow HID fogs. Perhaps I didn't make myself clear; the product I described is selective-yellow D2S and D2R automotive HID bulbs.
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