• June 5,2019.

Most LED headlight bulbs are very dangerous! Not only are they not as bright as the original bulb, they scatter light everywhere and blind other traffic. So are there LED bulbs that do work? Let’s find out.

The Trusty Halogen

First up. How good can the original halogen bulb be? For this test, we used an Audi A4 projector Headlight from the 2001 – 2005 model.


Taking an H7 bulb in the dipped beam we can first show you how bright an upgrade bulb is. For this, we used the OSRAM Night Breaker Laser +130% against a boarded-up office window.


Excellent. Now to understand what makes this a good headlight we must label certain portions.


The Cut-Off

First up we have the cut-off. This is arguably one of the most important features of a dipped beam headlight and stops you blinding other traffic. Because this is a projector headlight it has a very defined cut-off. All dipped beam headlights have a cut-off but some are less sharp than others.

The Step

Then we have the step. The step is part of the cut-off and enables you to see further down your own side of the road without blinding the oncoming traffic. Because we drive on the left in the UK the cut-off is higher on the left. If this was a headlight unit from the rest of Europe or the USA the cut-off would be higher on the right.

The Hotspot

Finally we look at the hotspot. This is where the bulbs light is most concentrated and its position in relation to the cut-off is very important.

The job of a dipped beam headlight is to illuminate the road as far in front of the car as possible without blinding other traffic.

Often, people think a lot of light right in front of their car is a good thing, but it’s actually counter-productive. The closer the light is to you the more your eyes close up to compensate, then your distance vision is reduced. This is similar to the effect of trying to look out your window in the dark from inside your house with the lights on. It’s much easier to spot that thing outside with the lights off. For this reason some cars are wired to turn their fog lights off when the high beams turn on. Therefore we want the hotspot of the bulb to be as close to the cut off as possible.

To make the hotspot easier to see we’ll look at the light heat map. The red portions are the brightest and the blue/purple areas are where there’s little to no light.

So what’s the issue with LED then?

The Surge of LED Headlight Bulbs

Here we see an H7 LED headlight bulb for just £29.99 from Amazon or eBay…a bargain right?

But is it really that easy? For just £29.99 can you have 8000 lumens PER BULB? The short answer is no.

The lumen claims are normally “calculated” based on the voltage they are running and not actually measured. But it’s still not as simple as that. Lumen values are just a measure of the total light emitted, it gives no indication of where that light is going to end up in front of the car! You could have 8000 lumens from a bulb like that and none of it would end up on the road, as we’ll explain.

We’ll start with this, the common spotted “Cree LED Headlight”. It’s important to note that Cree as a brand don’t make LED headlights, they make LED chips for all applications, mainly household LEDs. Don’t get me wrong, Cree is one of the market leaders of LED chips, but in terms of creating an LED headlight that works, that is down to the lamp factory, not Cree.

The problem with this bulb is immediately obvious when you compare it to the original halogen bulb. It may have the same shape base on it as the halogen bulb but the similarities end there. Just look at the size of the LED chip (the yellow bit) compared to the filament coil of the original halogen bulb. The light is not going to be anywhere near the correct place. But let’s fit it and find out…

Oh, another fundamental flaw! Its’ giant size meant that it couldn’t physically fit in the opening of our projector headlight. That £29.99 bargain isn’t looking quite so great now!

This size issue will apply to 99% of projector headlights and is a very important first hurdle for LED headlight bulbs to overcome. You can’t use all of those extra lumens if the bulb won’t actually fit. This also applied to our other Cree "big chip" LED.

Eventually we found a headlight they’d fit in and this was the result…

This was a dipped beam headlight so there should be all the things we labelled. A cut off, a step, a hotspot. But none of it is there, just a big blob of “glarey” unusable light. This is simply dangerous and should be avoided at all costs!

So let’s move on to a style that’s actually considered beam pattern.

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