I notice that the new Audi's and BMW's have some PRETTY blue HID's. Does anyone know the number to those? I don't care for the super white ones, I think the bluer, the better...

 

Depends on what your goal is. Do you want to see better and not annoy other drivers with excessive glare, or do you just like the pretty blue lights?

There's plenty said on this topic on this board...do a search on threads about HID and Xenon lamps.

Anything that claims to be more than 6000K, ignore. It's physically impossible and the lights will be crap. Stick with name brand like Osram-Sylvania and Philips.

My main concern with headlights is always safety. Do they give me good light of the road in front of me? Do they avoid blinding other drivers by being correctly aligned, having no color bleed, and a distinct cutoff line? Are they using the correct color spectrum (i.e. closely resembling natural sunlight in frequency)?

Ral

 

The superwhite lamps achieve the blue color by using a dichroic filter to filter out yellow light (the bulb looks blue but is actually filtering out yellow light). This is very counterproductive because most of the light produced by an incandescent bulb consists of yellow light. Only a very small small percentage of the total energy is in the blue part of the spectrum. Therefore, making an incandescent bulb look blue means most of the available energy is simply filtered out and wasted. In other words, you cannot add more blue to make it look blue you can only filter out other colors (mostly yellow) to raise the relative percentage of blue light.

PIAA and other vendors claim their superwhite bulbs are brighter. This is very misleading because, due to the yellow filter, they actually put out less total energy. They are able to make this claim because they narrow the beam so one small area actually does become brighter. Unfortunately this is at the expense of the important peripheral areas that now recieve much less light.

The superwhites might be cosmetically attractive to some but in fact are not as safe as a standard high quality bulb. Real HID headlamps actually put out true white (not blue) light that looks white from within the car. It has no blue tint to it. They only give a blue appearance when looking directly into them. This is because there is a very small spike of blue light energy at the high end of the spectrum. It is such a small amount of energy that lighting engineers refer to the blue light content as "throw away light" and take no credit for it in the design of the beam pattern.

Please do not compromise saftey with the superwhites simply because they are supposed to give the appearance of real HID lamps,

 

RhoXS, that was some good info. My thing is this-- Why would a company like BMW have blue-looking HID's if they weren't efficient? It isn't hard to tell that the X5 and the 3-5 series lights are appearing blue, why wouldn't they go with superwhites? Also, you seem to know alot about headlamps. Does the GS4's headlight glass have a tint on it that makes the OEM HIDs look blue-greenish?

 

The short answer is that BMW, or any other manufacturer for that matter, does not intentionally makes their HID ight sources look blue. Now the long answer.

An HID light source is very different from an incandescent light source. The superwhites are all incadescent light sources. Specifically they use a quartz-halogen system with a very hot glowing filament. Xenon gas is sometimes used in the quartz capsules (in addition to the halogen gas). Most of the light generated by an incadescent filament is in the yellow wavelengths. Very little of it is in the higher frequency blue wavelengths. Therefore, to make an incadescent light source look blue, you must filter out much of the yellow so the blue becomes more predominate.

An HID light source does not use an incadescent filament. It uses a high voltage electrical arc (continuous spark) between two electrodes to produce a very bright white light (hence: High Intensity Discharge). The HID capsules also use Xenon gas but for a different purpose. The spectrum of light emitted from an HID source more or less consists of a relatively even amount of all frequencies from red through blue. That it why it is true white light, like daylight.

HID sources only have a blue appearance when looking directly at them. The areas they light up look pure white. You see not even a hint of blue when sitting in the car or looking at the illuminated surfaces.

The blue that you see when looking directly at them is not intentionally put there. It simply comes from a small spike of blue energy that exists at the high end of the energy spectrum produced by the arc. There is not sufficient blue energy to change the overall true white color of the light. However it is enough, due to its interaction with the glass optics, to be noticed when looking directly at the light source.

One of two style HID capsules is used in all HID units. Both capsules are almost identical except one is intended to be used with reflector type assemblies and the other with projection designs. The bulbs, used by all the major auto manufactures are made by either Sylvania-Osram or Phillips. The point is that BMW does not design or make the actual light source and therefore has no control on the characteristics of the light produced. They only design and make the assembly that the capsule is used in.

HID light sources are clearly superior to incadescent sources because they put out much more light and use much less energy. This is the reason they are so desireable to use. A lighting engineer needs as much light as possible to illuminate both the road ahead of the vehicle and the all important shoulder and other peripheral areas. Since any light source only produces a finite amount of light, they have a limited budget of light to work with. An HID lamp is very desireable because it gives the lighting engineer a much richer light budget so he can do a much better job lighting up the necessary areas. I hope it can now be seen how inanely silly it is to take an incadescent source, that has limited light output to begin with, and then artificially limit its output much more by filtering out the yellow energy, just so it looks blue.

One more thing just so no one is confused. The superwhites ARE NOT HID lamps. There light output is crippled so they have a blue color and give the appearance of being an HID lamp. A true HID lamp emits true white light, not blue light, even though they give a blue appearance when looking directly into them.

I hope this answers your question. I also hope I did not ramble too much but just got home from work and the Chivas and water my wife made me definetly has kicked in.