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Why can't I see?_A theory on LED headlights.

6K views 9 replies 6 participants last post by  Loboc 
#1 · (Edited)
EDIT: This is a discussion about using the "high beams" or "brights" over a distance. This does not apply to "low beams" or "shuttered" projector bulbs.

You just sprang for a fancy new set of LED headlights, they looked great in the garage and you can't wait to try them out at night but the first time you hit the road you may feel a sense of disappointment and a disquieting sensation that the headlights aren't lighting up the actual road the way you feel they should.

This happened to me, my subjective human senses were insisting that there was this large black area down the road that simply wasn't being lit and that felt useless and unsafe.

However, when I resorted to some objective instrument based measurements of distance and light, I discovered to my immense surprise that in fact I could see test objects at much further distances with the LED vs the Halogen lights, even though my brain kept insisting that there was a huge dark hole in the lighting.

How could this be possible? I have a theory that it has everything to do with how the human brain and eyes interpret contrast.


This theory is my attempt to try and explain the effect.









Another example of the contrast illusion is demonstrated on this webpage.

This may also be why I'm so pleased with the "hexfire" light add on I just did, because I aimed the center spotlight parts of those lights down the center of the road, creating a "hot spot" much like the pattern of the traditional incandescent/halogen bulb.
 
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#2 ·
Brighter lights won't help as the headlights have these eyelids which prevent the bulbs from shining too far up to blind oncoming traffic. Just take the car on a hilly road and look at how there is a distinct abrupt dark line above where the lights end. While parked in your garage, have a friend turn on and off the high beams and you will see the eyelids in action. You can adjust the eyelid height, but be careful, going too high will blind oncoming traffic and get you tickets from America's finest.
 
#5 ·
My '14 ELR is WAY better than the previous '13 Volt. The automatic dimmers are the best I have ever used.
 
#6 ·
Doesn't the ELR have separate High and Low emitters? That would mean extra light being added to the equation, unlike the Volt with it's single projector and shutter setup.
 
#10 ·
Doesn't the ELR have separate High and Low emitters? That would mean extra light being added to the equation, unlike the Volt with it's single projector and shutter setup.
Yes. The array looks to be several on each side.
 

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#7 ·
It's an interesting idea and well illustrated. I suspect the color temperature and spectral distribution differences between the two might also play a role in this.

It is also interesting to note that the Gen 2 has LED low beams and halogen high beams, which might combine for the "best of both worlds." They certainly seem to work well.
 
#8 ·
Bright headlights are over-rated anyway. Their main effect is to blind oncoming traffic. Eyes adjust to the light level, the pupils dilate, the retinal cells increase sensitivity, and you end up seeing more if there are fewer 'hotspots' around.

On a bright moonlit night (tonight would be ideal, brightest 'supermoon' in decades) if you are on a quiet moonlit road, turn your headlights off. You'll be amazed at how much MORE you can see!!

... I'll let you decide how fast you are going, or whether to stop, when you do that for the first time!!
 
#9 ·
That doesn't work so well when a lot of the traffic coming towards me has blindingly bright headlights, often mis-aimed. It is like an arms race around here. Many cars on the road seem to be equipped with factory HIDs, or for older cars, the owner has upgraded his bulbs or added additional lights. I need some decent headlights to be able to see against that glare.
 
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