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  1. #1
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    What's the benefit of yellow fog lights? Or purely cosmetic?

    I've been seeing alot of people on the forums w/ yellow fog lights. Is there an actual benefit of having yellow over the normal white? And is a yellow hid's brighter than a super white hid's? I think it looks cool....just different from everyone else. Also when you have both low hid's and yellow fogs it seems like it would look really weird with those color combos. Is it really bright aka fuctional. Anyone w/ this setup/info give their opinions... Pros and Cons, thanks
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  2. #2
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    Traditionally (old school) fogs were yellow and driving lights were white.

    Personally i prefer yellow in fog/snow (bad weather) .

  3. #3
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    Yellow light is better able to penetrate fog, while white light has a greater tendency to be reflected by said fog. Same reason High Pressure Sodium lighting is preferable to Metal Halide in applications where fog is likely to be present often.
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  4. #4
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    You know where I can get a yellow fog hid kit? Or will just changing the halogen bulb be good enough? Would like a hid kit if I can find a quality setup. Also do I need to change the actual light from a clear lense to a yellow lense?

  5. #5
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    pretty much every where that sells HIDs has 3400k kits and those are as yellow as I've seen for an HID kit. Never seen them in person though.
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  6. #6
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    I have a set of 65 W, 2500K, 9005's installed as fogs. They are ebay sourced from NOKYA. Fantastic in snow storms. I also have fogs in the rear like the Euro 300's to make sure I can see and be seen.
    Last edited by Montreal300; 02-05-2012 at 11:10 AM.

    inTune 91 CAI, MDS indicator, ESP/BAS defeat switch, Tranzformer, blacked out wire mesh grille, smoked and flashing side markers, 9005 2400k 65W fogs, Euro rear fogs, debadged and demolded, 255/45/20 Nitto 420's, Boss 338 wheels, painted calipers. Glovebox, ash tray, door pockets, overhead console & cup holder LED additions. Blastin Bob 6db reso delete pipes. Euro LED side signal repeaters, 55/35 window tint, BT catch can. Color matched tail lights. Custom front lip. LED interior lighting. BT interior stuff. Lowered on BCR Coilovers. Front mounted parking sensors. 180 degree T-stat.

  7. #7
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  8. #8
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    ^^Maybe, yellows are extremely mellow toned and don't shine as far. I bet it's just a typo though.
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  9. #9
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    Sep 2007
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    Ahhh - physics!

    There is no good reason why fog lights are yellow. Here is an excellent explanation provided by Professor Craig Bohren of Penn State University:

    "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:
    Do Fog Lights Really Work?, Alaska Science Forum

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  10. #10
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    What is Selective-Yellow Light?
    It's what happens when you subtract blue from the output of a lamp producing white light. But first, what means "white light"? Under US Federal Motor Vehicle Safety Standard number 108 and Canadian Motor Vehicle Standards 108 and 108.1, headlamps as originally installed on motor vehicles (and as installed by anyone other than the vehicle owner) must produce white light. The relevant SAE (and identical ECE) color standards define "white" light as a rather large range within the CIE 1931 colorspace. That's why both brownish sealed beams and bluish HID headlamps are considered "white". It's also why "blue ion" or "crystal blue" bulbs with blue-pass dichroic filters sold to poseurs who want to try to pretend they have HIDs are not considered "white". The light can tend towards a yellow tint to a certain degree and still qualify as acceptable "white" light.

    In 1936, the French for tactical reasons wanted a way to identify the registration nationality of vehicles at night. However, they did not want to reduce roadway safety, and wanted in fact to improve it if possible. So, they figured to remove the blue from the output spectrum of their vehicles' front lamps. Some technical papers out of France on the subject can be had here and here. White light with the blue component subtracted is known as "selective yellow" light. It is a pure yellow color with little or no orange component—hence the French yellow headlamps. Yellow lamps have consistently over the years been subjectively ranked as better in poor weather and lower in glare than white ones, but is the effect real? Or is it just a subjective impression? One problem with this conclusion as drawn from the French experience with selective-yellow headlamps in France is that when the question was being considered, the lamps that were being compared with white lamps reduced the absolute intensity of the beam by about 12 percent. This fact may have had a part in reducing the glare. Because the requirement for yellow light no longer exists (though it remains allowed in many countries) we probably will never know the vagaries of the answer to this question.

    What explains the persistent subjective preference amongst experienced poor-weather drivers for yellow fog lamps, despite decades of white fog lamp prevalence? Selective yellow light can improve a driver's ability to see in fog or rain or snow, but not because it 'penetrates fog better' or 'reflects less off droplets' as is commonly thought. That effect is known as Rayleigh Scattering, and is why the sky appears blue. However, it occurs only when the droplet size is equal or smaller than the wavelength of the light, which is certainly not the case with ordinary fog, rain or snow. Roadway Fog droplets are several orders of magnitude larger than visible light wavelengths, so there's no Rayleigh Scattering.

    So, why do yellow fog lamps seem to work better? It's because of the way the human eye interacts with different colors of light. Blue and violet are very difficult for the human optical system to process correctly. They are the shortest visible wavelengths and tend to focus in front of our eyes' retinae, rather than upon it. To demonstrate this to yourself, find a dark blue store front sign or something else that's a dark, pure blue against a dark background in the absence of white light—from any appreciable distance, it's almost impossible for your eyes to see the blue lighted object as a sharply defined form;the edges blur significantly. Deep blue runway lights exhibit the same effect; check it out the next time you land at night. Blue also is a very difficult color of light to look at; it stimulates the reaction we call glare. Within the range of allowable white light, bluer headlamps have been shown to be 46% more glaring than yellower ones for a given intensity of light — see studies here and here. So, it seems culling the blue out of the spectrum lightens the optical workload and reduces glare. For a more detailed examination of this effect with respect to driving in foul weather, see Bullough & Rea's study on the topic.
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  11. #11
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    Quote Originally Posted by ToDieFor View Post
    65w????????
    Quote Originally Posted by CharonBLK07 View Post
    ^^Maybe, yellows are extremely mellow toned and don't shine as far. I bet it's just a typo though.
    Nope no typo.

  12. #12
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    In case you think I'm kidding. I'll say one thing and that is the white fogs actuall hurt my eyes in a snow storm these don't.
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  13. #13
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    i have the same bulbs in my fogs except they arent 9005. i didn't realize they burned hotter than normal bulbs. i had the gts fog covers on at the same time and it melted them to my fog lenses. i'll probably just switch to hids when i replace the lenses.
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  14. #14
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    Here is my car with 55w yellow HIDs next to my Dads with factory fogs. The picture dosen't show how bright they really are.

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