# HID colour temperature



## ianb (Mar 10, 2006)

I have a little undertanding of HID lights, I have a 6000k conversion for my car headlights(adjusted properly so I don't blind anyone else!), they are a little bluer than I was expecting, I know ~4200k is OEM headlight output, closer to sunlight. 
What I don't understand is how do you get the different colour temperatures? Is it the ballast or the lamp (arc size/distance)? Can I change my headlight to 4200k without changing the ballast?
Also I'm looking to get a handheld HID light and wondered if the lamps are changable or would the ballast need to be changed too?

thanks, Ian B


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## markdi (Mar 10, 2006)

all you need is different bulbs

like phillips 85122


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## Waterfish (Mar 10, 2006)

ianb, you'll want to be careful with those "HID headlight conversions". 

The results vary from car to car, where some vehicles actually make decent use of a set of HID bulbs stuffed into the current housings. 

Certain vehicles, no matter how low you aim them, will spurt out light in all different directions. 

What you may want to eventually consider is a proper "HID retrofit" where you take the projectors of BMW's, Mercedes, or Acuras, and actually insert those into your current headlights. Then, you essentially have a perfect OEM HID system built right into your headlights. 

Here's mine(stopsign is my username):

http://forums.bimmerforums.com/forum/showthread.php?t=441173&highlight=tsx

Remember-- I originally had a HID aftermarket kit with halogen projectors! HID projectors and halogen projectors are indeed different.


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## Anto (Mar 10, 2006)

The color from OEM Projector HID's come from both the bulb kelvin rating, and the projector optics. With D2S bulbs, they experience what is known as "colorshift". After the initial 100-500 hours, the output color changes from a yellowish-white to a crisper bluer tone. Remember, the higher K you get (past 4150k), the lower your LUMENS are going to be. OEM Philips bulbs come in two main ratings - 

85122 - 4150k (3200 Lumens)
85122+ - 5000k (3100 Lumens)
Both are the D2S bulb types.

The 85122+ was initially designed to be a replacement on older cars that had blown one bulb. Both the 85122 and 85122+ bulbs initially start out having yellowish-white output, but the 85122+ colorshifts much faster, to match the color of the other (colorshifted) bulb. You'll probably see many of these cases of colorshifted bulbs on the older 5-Series BMWs. The 85122+ bulb, amazingly, nearly matches output of the OEM 85122 bulb. With an HID kit, you're probably going to be looking at a ~500 lumen loss with 5000~6000k bulbs, instead of the 100 lumen loss with OEM hardware.

Color on OEM HID's come mostly from the projector optics. Ever been driving, and see a car's headlights flicker from purple to blue to white? That's the projector creating the color. Color exists in the "cutoff" line. Here's a picture (taken from HIDplanet.com):







See the compression of purple and blue colors? That's what the color comes from on projector-type setups. Also notice how the OUTPUT color is pure white. It's not colored blue or anything like that.


Now, in your situation, it's entirely different. Since HID kits do not utilize a projector, all the color comes from the bulb. Output suffers slightly due to the blue tinting that's casted on the bulb face. 6000k would be very very blue on the K color scale. If you change out your bulbs to around 4150/4300k, then you'll have more white-ish output. Ballasts have nothing to do with the color.

As far as ballast interchangeability, most all of the OEM D2S hardware is interchangeable. Bulb bases are the same, ballast/bulb connector plugs are the same, etc. The only difference is the projectors, and the ballast design. 

Again, with kits, you have to get the kit-specific bulb and ballast, should one blow. Kits usually come with different connector plugs, so if a bulb blows, you have to get the bulb that has the same plugs for a replacement.


Bottom line is: 
OEM HID setups create most of the color from the projector.
HID Kits create it from the bulb.
Yes, you can change your bulbs to ~4200k without changing the ballast, as long as the bulb fits your ballast.


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## ianb (Mar 11, 2006)

Always a pity when problems you didn't even know about come up!

Waterfish, thanks for that information, as I was just looking at some Halogen projectors that fit my car, but definately won't get them now. I would probably agree that they due give out more than a proper retro-fit. I just wish I hadn't spent so much on them already! I have H4 fitment so I will have to look into a suitable retrofit that might squeeze in.

Anto, thanks for all the colour temp information, you can always rely on the good people here to share their knowledge.

thanks, Ian B


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## mattheww50 (Mar 11, 2006)

ianb said:


> ...What I don't understand is how do you get the different colour temperatures? Is it the ballast or the lamp (arc size/distance)? Can I change my headlight to 4200k without changing the ballast?
> Also I'm looking to get a handheld HID light and wondered if the lamps are changable or would the ballast need to be changed too?
> 
> thanks, Ian B



Actually sunlight is more in the range of 5000-5400K. However a standard halogen head lamp is in the 2800-2950K range, so a 4200K HID looks much 'whiter'. You can get higher the 2950K with a halogen lamp, but it is either done with a filter, or by shortening the lamp life substantially.

You get different colour temperatures from the HID lamp by tweaking the mixture in the arc tube. and perhaps the size and shape of the arc. In general a D2S ballast will work with any D2S lamp, regardless of colour temperature, and D2S lamps are available in a wide range of colour temperatures, generally the higher colour temperatures are lower output, and the higher the colour temperature, the more blue the output. For example open shade has a colour temperature of about 7000k from the blue sky, perhaps higher


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## XeRay (Mar 11, 2006)

mattheww50 said:


> Actually sunlight is more in the range of 5000-5400K. However a standard halogen head lamp is in the 2800-2950K range, so a 4200K HID looks much 'whiter'. You can get higher the 2950K with a halogen lamp, but it is either done with a filter, or by shortening the lamp life substantially.


 
As a "4200K" bulb "breaks in" (50-100 hrs of operation), the color temp shifts up closer to 5,000K. More like daylight white.


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## ianb (Mar 11, 2006)

XeRay said:


> As a "4200K" bulb "breaks in" (50-100 hrs of operation), the color temp shifts up closer to 5,000K. More like daylight white.



so I guess in the same respect my HID conversion is likely to shift from the 6000k and become even more bluer! Oh poo, kind of get to the stage where I wish I was still ignorant with nothing to worry about 
Now I want to just take them out and put the standard Halogen back in 

Still thanks for all the advice, its interesting to get a greater understanding of HID,

Ian B


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## Waterfish (Mar 11, 2006)

ianb, dont worry, I started with 5000k HID, then 4500K hid, then full projector retrofit with OEM 4100K!

The good news, is that if you choose to remove them and sell them, there's a pretty good bit of market of people to offload them to. I got exactly what I wanted for mine.


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## cmacclel (Mar 11, 2006)

I installed a set of OEM Hella ballast with some Osram 4300k bulbs in my stock 01 Explorer headlights and the first time it got foggy out the came out the next day! The stray beams of light projected a pyramid up 100 yards above the truck! If you do install them in a car that came with halogens you NEED to install projectors.

I have a set of KC Daylighter 6" stainless of road lights on there way to me. Hopefully there nice  at $1k+ they better be!


Mac


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## ianb (Mar 12, 2006)

Yes I think I am getting some spill, which would be quite impressive in the fog too, but as I am in danger of putting more money into my headlights (especially if I start projectors retrofit) than the cars worth  , I think I should try to save for the next car with standard xenons(who am I kidding), well maybe one which I could get them from a premium model and fit myself.
The idea of trying to get some projectors and then fit them to my headlights is a scary idea, I'm still tempted if I had half a chance.

but...
Waterfish, buying projectors are they from salvage yards directly from a scrapped car or bought new? If you start to fit them do you just carve a chunk from the rear of existing lights?

thanks, Ian


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## Kwizatz Haderach (Mar 12, 2006)

*Re: HID colour temperature for FOG LIGHTS ?*

I keep reading about how higher color temperature >6000K produces more glare for the driver in fog/mist.

The question I have is what color temperature is the most effective at cutting through fog?

Most HID sites talk about light position(ex. low to the ground) but nothing about color temperatue except some say "amber".

I've read here about HID's in the 3000K range. Anyone have any clues?


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## Orbit (Mar 13, 2006)

Question: Why are fog lights yellow? Does it help that they are? Does it matter if you are driving in city or countryside? 


Answer: My understanding is that it is important for fog lights to be one color 
(rather than white, which is all colors) because the different 
wavelengths(colors) of visible light scatter off the fog droplets 
differently. This phenomenon is known as "dispersion," because the 
different colors of light in an image will separate from each other, 
causing the image to "disperse." If you illuminate the road with only one 
wavelength (color) of light, the images of the objects you see will still 
become somewhat blurry because of the scattering of light by the fog, but 
at least you won't have extra problems from dispersion. So, if we want to 
use just one wavelength of light, which wavelength should we use? It turns 
out that light with short wavelengths scatters more than light with long 
wavelengths (short to long: violet, indigo, blue, green, yellow, orange, 
red). So, a long wavelength light will be best. There's another thing to 
consider, too: our eyes are not equally sensitive to all colors. It turns 
out that we are most sensitive to yellow and green light. So, our best 
compromise between sensitivity for our eyes and a long wavelength for least 
scattering is yellow light. 
A consideration used in street lighting is cost and efficiency. You 
may have seen some yellow street lighting in some places; this is 
"low-pressure sodium vapor" lighting. The special thing about this light 
is that it is almost entirely one (actually two very close together) 
wavelength of yellow light, and that it gives the most illumination for the 
amount of electricity. A big problem with this light, though, is that it 
throws off color perception. Under sodium vapor light, something blue 
looks gray. This makes it hard to, say, recognize your car in a parking 
lot. 

There was teh theory, now here is the reality. 

There is no good reason why fog lights are yellow 

"First I'll give you the wrong explanation, which you can find here and 
there. It goes something like this. As everyone knows, scattering (by 
anything!) is always greater at the shortwavelength end of the visible 
spectrum than at the longwavelength end. Lord Rayleigh showed this, didn't 
he? Thus to obtain the greatest penentration of light through fog, you 
should use the longest wavelength possible. Red is obviously unsuitable 
because it is used for stop lights. So you compromise and use yellow 
instead. 


This explanation is flawed for more than one reason. Fog droplets are, on 
average, smaller than cloud droplets, but they still are huge compared with 
the wavelengths of visible light. Thus scattering of such light by fog is 
essentially wavelength independent. Unfortunately, many people learn 
(without caveats) Rayleigh's scattering law and then assume that it applies 
to everything. They did not learn that this law is limited to scatterers 
small compared with the wavelength and at wavelengths far from strong 
absorption. 


The second flaw is that in order to get yellow light in the first place you 
need a filter. Note that yellow fog lights were in use when the only 
available headlights were incandescent lamps. If you place a filter over a 
white headlight, you get less transmitted light, and there goes your 
increased penetration down the drain. 


There are two possible explanations for yellow fog lights. One is that the 
first designers of such lights were mislead because they did not understand 
the limitations of Rayleigh's scattering law and did not know the size 
distribution of fog droplets. The other explanation is that someone deemed 
it desirable to make fog lights yellow as a way of signalling to other 
drivers that visibility is poor and thus caution is in order. 


Designers of headlights have known for a long time that there is no magic 
color that gives great penetration. I have an article from the Journal of 
Scientific Instruments published in October 1938 (Vol. XV, pp. 317-322). 
The article is by J. H. Nelson and is entitled "Optics of headlights". The 
penultimate section in this paper is on "fog lamps". Nelson notes that 
"there is almost complete agreement among designers of fog lamps, and this 
agreement is in most cases extended to the colour of the light to be used. 
Although there are still many lamps on the road using yellow light, it 
seems to be becoming recognized that there is no filter, which, when placed 
in front of a lamp, will improve the penetration power of that lamp." 


This was written 61 years ago. Its author uses a few words ("seem", 
"becoming recognized") indicating that perhaps at one time lamp designers 
thought that yellow lights had greater penetrating power. And it may be 
that because of this the first fog lamps were yellow. Once the practice of 
making such lamps yellow began it just continued because of custom." 


Also, take a look at the following web site: 
http://www.gi.alaska.edu/ScienceForum/ASF5/593.html


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## ianb (Mar 13, 2006)

Thats a great reply Orbit, I have always wondered why in France some of the cars have yellow headlights? I guess this may follow the same flawed ideas as can be thought of yellow fog lights, so I guess that the most effective fogs lights are low, bright ones?

Ian


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## Orbit (Mar 13, 2006)

well....yes and no....

how do you define bright??
you want the light source low to go "under the fog" so others can see you, but if the fog is to the ground you will want a light that is enough to penetrate the fog to some degree (it's easier to see a white car for instance with lights then it is to see a white car with no lights etc etc) also keep the source low so that the light doesn't get scattered directly back into your face,
but not so bright as to reflect significant light back at you have you tried driving at night in fog on high beam...not a very succesful venture.

the above is a very simplistic ream, but it's all i can muster atm, i'm tired and off to bed lol.
i've found the best way to traverse fog, in race conditions at anyrate, reguardless if night or day is to have relatively dim ie low beam and polarised sunglasses.

in the end fog lights are more about being seen then to see.

hope that makes some kind of sense.

ORB.


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## bfg9000 (Mar 13, 2006)

A 3000k HID lamp produces the most dazzlingly annoying, intense radioactive yellow color if you'd like to get noticed.

Didn't France recently outlaw cadmium in glass bulbs so that yellow glass could no longer be sold there? The yellow incan bulbs now have a yellow-orange coating that burns off over time.


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## Orbit (Mar 13, 2006)

i also forgot to add that as the light reflected during sunlight hours in fog is predominatley white, distungishing bewteen yellow and white is easier then white and white, so using yellow as a warning etc is reasonably sound.


sorry for the over simplification.


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## Kwizatz Haderach (Mar 13, 2006)

Great Reply Orbit! Thanks for the informed answer. I'm looking into fog light options for my Scion xA, and now I can base my decision on some real facts.


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