# Headlamp science Vs. opinion?



## B11sleeper (Oct 15, 2003)

In the HID thread some people are saying that the higher color temp HID's don't scatter in the rain as badly as the silverstar type halogens.

re: light wavelength vs scatter 

As shown above, yellow scatters less than blue.

Is the apparent difference in HID / Halogen because the HID's have more effective power output and better lenses? So they appear to light better than a lower wattage poorly focused halogen??


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## Radioaktiv (Feb 12, 2004)

i used to run hyper white/blue, but now i run yellow/gold lighting in the headlamps and fog/driving lamps

i wont ever run white/blue again


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## Binger (Aug 29, 2002)

Radioaktiv said:


> i used to run hyper white/blue, but now i run yellow/gold lighting in the headlamps and fog/driving lamps
> 
> i wont ever run white/blue again


Why?


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## potsdamcartel (Sep 14, 2004)

yes, physics is better than drugs


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## Radioaktiv (Feb 12, 2004)

Binger said:


> Why?


because i can see better
especially in the mist/rain/fog 

yellow light is much less refractive than white

i know there is some lighting experts here who can back me up with some more scientifical jargon


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## pete? (Jul 6, 2004)

i like to use hyper white (silver stars soon to be piaa) and driving lights but i am going to get some fog lights soon with amber/gold bulbs in them...........im gona look like a rally car lol i like sethwas take on lighting :thumbup: i like to be disgustingly over prepared


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## myoung (Apr 15, 2002)

There is a big difference between a true HID headlight system and "Hyper or Super White" bulb replacements.... Not the same thing.


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## lshadoff (Nov 26, 2002)

Rain and fog cause the light emitted by your car to scatter.

"Some of the headlamp light becomes "backscatter," light reflected back by rain to the driver's eyes. The backscatter acts as a veil and reduces contrast of everything in the field of view. The rain then blocks light coming back from objects in the road while simultaneous lowering their contrast by the veiling effects of backscatter. Backscatter also creates glare, which is defined as light much brighter than the driver's level of dark adaptation. Glare creates visual discomfort and lowers the ability to see contrast. Glare can impair vision for all drivers, but is especially bad for older people."

"When air particles become very small, the situation is more complicated because not all wavelengths are affected equally. Air molecules, for example, scatter short wavelengths (blue) may more, making the sky blue. This is why some experts advocate yellow fog lights. They believe that blue scatters more and that removing blue (to produce yellow) reduces the ability of fog to scatter lights. However, this is a mistake for two reasons. First, fog droplets are still far too large to selectively scatter light of different wavelengths, so yellow scatters the same as blue. Second, filtering the fog lights to produce yellow lowers their output and actually reduces visibility."
http://www.visualexpert.com/Resources/weather.html

The improvement in perceived vision by yellow light is physiological. Yellow lenses in glasses degrade color vision but enhance contrast. It is the enhancement in contrast which makes yellow lights better than white.
http://www.ncbi.nlm.nih.gov/entrez/...ve&db=PubMed&list_uids=10701805&dopt=Abstract

Lew


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## B11sleeper (Oct 15, 2003)

they mention something important down at the bottom there..

_Footnotes

1 Fog lights work by capitalizing on the basic principle, "angle of incidence equals angle of reflection." They are mounted low and project light directly along the road. As a result, there is little scatter back to the eye._

_learn to read...
since the color doesn't make any difference...
( I didn't know that. )
_

I'm still curious if real HID's perform better in rain and fog even though they are so blue.
(apparently they would because they have more light output. and color temperature has no effect...)


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## lshadoff (Nov 26, 2002)

Based on what I read, I think that wearing yellow "shooters glasses" (pale yellow) may help. These are worn by people who do serious target shooting.

Lew


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## potsdamcartel (Sep 14, 2004)

check out these sites: 

http://www.cartalk.com/content/columns/Archive/2002/February/08.html

http://www.newton.dep.anl.gov/askasci/phy99/phy99xx4.htm

what do pro rally cars use? yellow or white?


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## myoung (Apr 15, 2002)

B11sleeper said:


> I'm still curious if real HID's perform better in rain and fog even though they are so blue.
> (apparently they would because they have more light output. and color temperature has no effect...)


I think they do... My Altima has factory HID and it seems much easier to see in bad weather. Not to mention dark middle of no where highways.


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## Radioaktiv (Feb 12, 2004)

true HIDs are a whole different story
cuz they _are_ HID, high intensity discharge there is less scatter (from what i understand)


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## lshadoff (Nov 26, 2002)

Radioaktiv said:


> true HIDs are a whole different story
> cuz they _are_ HID, high intensity discharge there is less scatter (from what i understand)


What does high intensity mean? It means that the HID lights emit more photons, the basic unit of light. The photons are the same whether they come from a candle or a headlight, it's just their color that differs. It's well established that the scattering of light by fog particles is independent of the color of the light because the water droplets are too big to discriminate colors. So, some fraction of the light is back-scattered by fog. If more light hits the fog, more is back-scattered.

What counts is how the light is focussed. If it has a beam shape with a flat top, then it can be aimed to minimize back-scattering.

Lew


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## myoung (Apr 15, 2002)

lshadoff said:


> What counts is how the light is focussed. If it has a beam shape with a flat top, then it can be aimed to minimize back-scattering.
> 
> Lew


The factory HID's have a flat top beam


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## pete? (Jul 6, 2004)

myoung said:


> The factory HID's have a flat top beam


speaking of flat beam has anyone seen those supposed "flat beam fog lights?" they apparently produce a flat beam via a special lens. would these help at all? or would normal foglights with an amber bulb in them be better or! the flat beam fogs with amber bulbs! hmm


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## LIUSPEED (May 29, 2002)

those " special beam " projector basically use the concept of HID systems with plate that prevents any further light spread and a nice cut off.


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## Radioaktiv (Feb 12, 2004)

you know that coating thats on the tips of our regular 9004 bulbs?
anyone ever brushed/sanded that off?


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## pete? (Jul 6, 2004)

Radioaktiv said:


> you know that coating thats on the tips of our regular 9004 bulbs?
> anyone ever brushed/sanded that off?


i think that would be a terrible/ dangerous idea lol


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## B11sleeper (Oct 15, 2003)

there's no real benefit to that, it's there to block the direct light coming off the bulb, and your lamp housing has a metal reflector in front of the bulb anyways.


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## Radioaktiv (Feb 12, 2004)

im just wondering what would happen
what if you took the coating and deflector off

would it just blind everyone?


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## B11sleeper (Oct 15, 2003)

Radioaktiv said:


> im just wondering what would happen
> what if you took the coating and deflector off
> 
> would it just blind everyone?


if you did it, and didn't scratch the bulb and cleaned all the finger oil off, so that it doesn't explode, then what happens depends on whether your lamphousing has the metal shield in front of the bulb.

I think in theory, without the metal shield or paint, there would be a very bright spot in the center of the headlamp, and the cars driving towards you would probably hate you. Even the euro headlamps have the shield, so it must be useful. I'll look at headlamps in a bit when i go out for lunch.


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## Avshi750 (Jan 13, 2003)

living here in Pacifica (we hold the Fog Festival every year) i have had extensive experiences with seriously thick fog, like fog that i cant see out my back window when backing out of the driveway!

i had these PIAA dual fog lamps mounted in the standard B13 SE-R foglamp location on my Sentra before the Sunny bumpers went on...









has both hyper white and yellow H3 bubs... both VERY bright. 
and my new Mazda has HID headlights so i can testify to the affectivness of just about every type of bulb setup... but i am no scientist  

the white H3 bulbs from the PIAA lights were asking for DEATH in fog and rain, the light created a wall of white right in front of the car (lamps mounted very low remember)
the yellow H3 bulbs from the PIAA lights saves my ass more times than i can remember. the yellow light illuminated just about everything in fog or rain with no wall of light.
the HIDs on the Mazda put that whole PIAA lamp setup to shame!!! i can see everything, no wall of light and these are at the standard headlight level... a good foot to foot and a half above the level of the PIAAs.


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## B11sleeper (Oct 15, 2003)

^^ good input!


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## Radioaktiv (Feb 12, 2004)

aye
experience is the best teacher
thx man


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## Tickwomp (May 27, 2003)

ive noted that with bulbs with more yellow in them *i.e. halogen vs hyper white or whatever* reflects better off the ground. its usually pretty wet here and its easier to see yellow-ish light reflecting off the ground than white light. HIDs however light up everything, even when its wet. just my .02


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## pete? (Jul 6, 2004)

ok well i was going to start a new thread but then remembered this one from a while back. so im all set (lighting wise) in good weather on dark roads (silverstars and 55watt driving lights) but now i need some fog lights and i remembered all of this talk about flat beams and what not. so do you think these would work or does the flat beam pattern only work with HID lighting? if you think these arent worth it ill just end up getting projector amber colored fog's. take a looksy


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## asleepz (Feb 24, 2004)

lshadoff said:


> What does high intensity mean? It means that the HID lights emit more photons, the basic unit of light. The photons are the same whether they come from a candle or a headlight, it's just their color that differs. It's well established that the scattering of light by fog particles is independent of the color of the light because the water droplets are too big to discriminate colors. So, some fraction of the light is back-scattered by fog. If more light hits the fog, more is back-scattered.
> 
> What counts is how the light is focussed. If it has a beam shape with a flat top, then it can be aimed to minimize back-scattering.
> 
> Lew


I could've swore it was Lumens. HID puts out so much more light it's not even funny no HID look a like or halogen bulb comes close to putting out as many lumens as TRUE HID. From the angle HID does look blue/purple but when your in the driver seat it isn't as intense of that color. You can get 4300K HID projectors and turn them on get at a rough 45 degree angle and they are going to look blue/purple. Get right in front of them they are a intense white.


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## lshadoff (Nov 26, 2002)

SKD_Tech said:


> I could've swore it was Lumens. HID puts out so much more light it's not even funny no HID look a like or halogen bulb comes close to putting out as many lumens as TRUE HID. From the angle HID does look blue/purple but when your in the driver seat it isn't as intense of that color. You can get 4300K HID projectors and turn them on get at a rough 45 degree angle and they are going to look blue/purple. Get right in front of them they are a intense white.


Lumen is a measure of the intensity of a light source over a given angle. If there are two sources of light with the same number of watts, and one is focussed in a narrower beam than the other, the one with the narrower beam has a higher lumen value.

A good discussion of this is here. 

Lew


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## IanH (Feb 11, 2003)

potsdamcartel said:


> check out these sites:
> 
> http://www.cartalk.com/content/columns/Archive/2002/February/08.html
> 
> ...


I watch WRC and under the conditions I have watched on TV and in person at the WRC in Wales they are very bright but white. (including rain and mist in Wales in November) 
good Luck.....


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## pete? (Jul 6, 2004)

IanH said:


> I watch WRC and under the conditions I have watched on TV and in person at the WRC in Wales they are very bright but white. (including rain and mist in Wales in November)
> good Luck.....


yes and it is HID, HID is differant than halogen in that it dosent reflect as much (i think this was accually in this thread......or maybe another one idk) but for the best in bad weather its either HID or light yellow.


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## Marvin (Oct 16, 2002)

I've tried and tried and tried to find a true yellow bulb for my fogs, but i've yet to find one. 

However, that being said, I will never ever buy another car w/o true HID's. Everything is so much more crisp and bright.

I try not to drive in the rain as much as possible, so I can't really attest as to the differences in halogen vs. HID. I'd like to say that HID's are much better just in terms of lighting up the road. The backscatter theory is interesting, however.


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## pete? (Jul 6, 2004)

Mark said:


> I've tried and tried and tried to find a true yellow bulb for my fogs, but i've yet to find one.
> 
> However, that being said, I will never ever buy another car w/o true HID's. Everything is so much more crisp and bright.
> 
> I try not to drive in the rain as much as possible, so I can't really attest as to the differences in halogen vs. HID. I'd like to say that HID's are much better just in terms of lighting up the road. The backscatter theory is interesting, however.


have you tried HELLA? they make a yellow bulb or so i have heard. also try rally racing prep sites (they sell rally gear) im 100% sure that is where you would find what you need. it would be like a tuner specific site (like nopi or what ever) but for rallying, maybe a subby forum could help you out with that.


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## asleepz (Feb 24, 2004)

I'm going to get the Xenarc X110 kit on my Z.... Our Altima does great in the rain with it's HID's but they aren't in projectors so I don't know if the light distribution would play a vital role in it. But I do know my "Hyper Blue" POS lights in my car fried my wiring pretty much and suck ass unless they are on brights.


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## pete? (Jul 6, 2004)

hper blue allways suck........the only reason HID looks blue is because of the prism effect its a truw white light. but cars that have HID without the projector have a special reflector, any old reflector wont do, im sure you could get a retro fit done with projectors for the 300 and it would be even better than the alty's :thumbup:


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## LIUSPEED (May 29, 2002)

phillips have a hyper yellow HID fog light bulbs IIRC.

3100 K i believe it is.


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