Adaptive Headlights

In article >,
Dave Plowman (News) > wrote:
>In article >,
> Richard Sexton > wrote:
>> > But plenty of boy racer types replace standard incandescent bulbs with
>> >blue incandescent types for the reasons boy racers have - they're
>> >actually
>
>> They're actually very illegal.
>
>I don't know the law in your country.

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).


--
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Richard Sexton | Mercedes stuff: http://mbz.org
1970 280SE, 72 280SE | Home pages: http://rs79.vrx.net
633CSi 250SE/C 300SD | http://aquaria.net http://killi.net

John Carrier wrote:

> Adaptive headlights pivot the beam slightly for turns and curves. Don't
> have them myself, but I'd think they'd be useful.

They are. They improve seeing range in curves and turns.

> HID low beams are a real plus.

*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.

> BMW marketed dual Xenon for awhile in which the HID bulb had a mask that
> would rotate around the filament when high beam was selected and allow an
> HID high beam

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.

> These can be found in the aftermarket.

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
http://www.danielsternlighting.com/t...nversions.html

> You can also install higher output Halogen bulbs (if you don't have or don't
> want HID), but if the wattage is too great, you'll risk deforming the
> housings and lenses from the extra heat and they also might stress the
> electrical wiring.

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.

> Beware of the blue tint bulbs. Most tend to put out less light than the
> somewhat yellowish halogen units.

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).

DS

Richard Sexton wrote:

> >The factory OE Xenon adaptive headlights is an excellent option for
> >those needing better night vision and at what, about $800, is a
> >BARGAIN. I pity the fool who passes on this bargain and then later
> >decide he wants it.

> Well, in all fairness it is possible to install halogen driving lights
> that will light up the road better, cost at least half as much, won't
> give you nast backdazzzle in inclement weather and aren't as offensive
> to oncoming drivers.

Naw, it isn't. "Driving lamps" are auxiliary high beam lamps, never
safe or legal for use with low beams, in traffic, or in inclement
weather.

DS

Dave Plowman (News) wrote:

> Discharge lamps of the type used on cars can be any colour temperature you
> want.

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.

> However, the eye is more sensitive towards the blue end of the
> spectrum than it is to the red,

The human eye is most sensitive to yellow-green.

DS

Dave Plowman (News) wrote:

> Currently, the most efficient HID lamps do look blue compared to halogen.
> But are in fact closer to daylight.

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.

> Then you really need custom foglamps. Which could use an HID lamp.

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.

DS

Dave Plowman (News) wrote:

> It's most sensitive to green of the three primaries. But more sensitive at
> the blue than red end - at either side of the roughly centre green.
> We're used to tungsten filament lamps being towards the red end of
> daylight - which is probably why many HID types look blue in comparison.

No, automotive HIDs look blue because of the high spikes in the blue
and near violet ranges of their SPD.

DS

Dave Plowman (News) wrote:
> high efficiency discharge types will be the way forward
> - as well as LED for low powered applications.

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.

> the sure thing is the tungsten filament bulb's days are numbered.

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.

DS

Richard Sexton wrote:

> The longer the wavelength of light the less is scatters in fog. This is why
> fog lamps are yellow

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.

DS

Dave Plowman (News) wrote:
> Richard Sexton wrote:

> > HIDs ARE great, but, they have a lot of problems with automotive
> > applications: they don't come on instanly and a lot has to be done to
> > get around this.

> Err, how often does it get dark suddenly? I've never found the time they
> take to get to full output a problem.

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.


> They produce approximately three times the light for the same current -

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.

DS

Fred W wrote:

> I thought your desire for "instant on" was in regard to switching on the
> high beams.

Legal regulations worldwide call for instant-on low and high beams (to
greatly simplify the requirements, which are rather more complex).

> I usually turn my low beams on long before actual dark and if they took
> a minute or longer to turn on, it would be no big deal.

Automotive HIDs take about 60 seconds to attain full intensity.


> Your Cibie's don't fit in any modern cars. When was the last car made
> that takes 5.25" round headlamps. They are also only available for
> "wrong-hand drive" applications, as far as I can see.

They are available for both LHD and RHD applications.

> Comparing them to
> factory Xenon HIDs (in the US anyway) is kind of moot.

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:

http://dastern.torque.net/Photometry/Cibie_CSR_Iso.jpg

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 he

http://dastern.torque.net/Photometry/Cibie_CSRH_Iso.jpg


> But my point was (is) the color doesn't *have* to be a problem. 4300k
> HID is not blue in the least.

There are actually high spikes in the blue and near-violet of the SPD
of standard-production 4100k-4300k automotive HIDs.

> And I have yet to see a car manufacturer offer up any car with halogen
> lights that come anywhere close to the light output of the 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!

> Sure, they can be improved going forward, and I'm sure they will. But
> they're already better than all the alternatives.

Potentially, not necessarily.

DS