LED / Xenon.

Fancy some Angel Eyes, want to get rid of that yellow glow, want info on LED's, got a problem with your headlights, get your answers here

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Octavius
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LED / Xenon.

Post by Octavius »

So.
I’ve never owned a BMW with Xenon headlights and my current car, F30, has LED ones.
There’s a few posts on the forum with members buying cars equipped with the Xenon’s saying they are disappointed with the lumen output.
So, two questions.

Are the Xenon lights not as expected due to deterioration of lamps with use.

What’s better. LED or Xenon. ( for people that have had both )
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G90
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Re: LED / Xenon.

Post by G90 »

Generally the xenon (hid) bulbs last a while but lumen output reduces considerably with age, also the bulbs produces more blue light with age which shortens the wavelength of the light. Not many people change them out of due course just when they eventually stop working. LED'S are the same in that basic sense however usually its a component of the lighting system that fails before the LED chip.
The LED itself also loses brightness with age, if it was for example a 10000 hour life. At around 10000 hours the brightness would be reduced to around 80% +/- 10% of the original light output.

Eliminating headlight design variables etc the xenon is the better source of light. You have a greater light penetration than similar output LED.
But as technology advances within the headlamp design world
There won't be much in it, how eyes perceive headlights colour temperature with age also varies. What i think people notice straight away is the LED headlamps dont have as intense a hot spot. As the hot spot is generally spread more and a little larger itself.
I always missed my xenons from back in the day as felt the colour temperature of the bulb had a longer wavelength and greater penetration than the adaptive LED (non voodoo lights) i have now.
But i wouldn't say its the be all and end all. We adapt...

The lack of headlight washers on a lot of LED units also plays a roll, have to wash my lights a lot in winter. Unreal how much salt and road grime is building up at the moment.
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CoupeSilver
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Re: LED / Xenon.

Post by CoupeSilver »

G90 wrote:
Sun Nov 17, 2019 5:19 pm
....
Eliminating headlight design variables etc the xenon is the better source of light. You have a greater light penetration than similar output LED.
....
What does that even mean? The lumens output is the definition of light intensity. How can two bulbs of the same lumens have different light penetration?? Penetration through what exactly? Or are you talking about something completely different?

By the way, the human eye normally is most senstive to the yellow end of green light with sensitivity dropping with frequency on either side of green wavelengths. So technically a red, green and blue bulb of the same power output, the green one would seem the brightest of the three. In fact the currently trendy near purple blue is the worst colour for perceived brightness with equal power output, even at night were the sensitivity curve shifts it's peak to the blue end of green.

https://light-measurement.com/spectral- ... ty-of-eye/
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G90
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Re: LED / Xenon.

Post by G90 »

You half answered your own question with the red green blue part. A 2000 lumen led for example will not have same optical intensity in the short and long wavelength sides of visible range as an 2000 lumen hid producing 6000k. So it may appear as bright at source but measured over distance the broader spectrum of current hid bulbs will mean the light can penetrate further within the realms of what are eyes can see.
Full or more broad spectrum LED'S will advance so none of this will be relevant in time to come. In terms of headlight bulbs.
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Nyxeris
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Re: LED / Xenon.

Post by Nyxeris »

Penetration through the atmosphere

https://en.wikipedia.org/wiki/Rayleigh_scattering

The longer the wavelength of light (i.e. the redder it is or the lower the colour temp in terms of headlight bulbs) the less it gets scattered by particles in the air, be it dust, smoke, water, whatever.

The effect isn't massive as lights are so bright now, but back in the day this was supposedly the reason headlights were yellow. The longer wavelength doesn't get scattered as much, so the lights perform better and don't reflect as much back at the driver - especially when it's foggy.
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G90
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Re: LED / Xenon.

Post by G90 »

This is why the hid with its broader spectrum of light penetrates further. Despite the perceived colour being the same, the spectrum of visible light produced by the arc is broader containg more longer wavelengths than equivalent led.
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CoupeSilver
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Re: LED / Xenon.

Post by CoupeSilver »

Makes sense. Thanks for the replies and clarifications.
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G90
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Re: LED / Xenon.

Post by G90 »

Nae bother👍
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