Everyone likes bluish headlights. Well, almost everyone. The question is how much blue is actually allowed. The answer is clear: none at all. Only white is allowed. Let’s look at why and when the blue tinge is still legal.

Laundry detergent ads try to tell us that whites can’t get any whiter. In fact, it’s optical brighteners in these products that make the clothes appear so white. Sadly, that doesn’t work with car lights.
With LEDs it’s still fairly simple. They’re basically blue anyway – at least in the versions for lighting. It’s only the yellowish-beige coating, called the converter, that changes the light to the desired color. But wouldn’t you be tempted to just choose the blue that’s already there? The Economic Commission for Europe (ECE) recognized this danger and put a stop to it in its regulations which are internationally binding, except in the USA. It’s the definition of ECE white, and it’s a precise one. It specifies exact coordinates in the color space. That means something to people who know their physics; but not to your average driver. They need information such as the color temperature in kelvin. High values mean colder light, in other words more bluish light. If you do some calculations, but again only if you have a talent for science, you’ll get around 6,000 kelvin as a maximum permissible color temperature. So if you see values for lamps offered on the internet that far exceed 10,000 kelvin, they’re plain and simply illegal. And the information is most likely incorrect.

Such high color temperatures are virtually impossible in incandescent lamps. You can’t get that much out of a filament. While an additional color filter can produce blue light, so much light gets lost that the lamp would only produce a glimmer. Simply increasing their electrical output in watts and the luminous flux in lumen is no solution either, at least not a legal one.

It’s different for the blue ranges from brand manufacturers. For example, halogen lamps from Osram’s Cool Blue® Intense series not only deliver about 4,200 kelvin that can be reliably measured but also produce good light. This color temperature required a lot of developing and finetuning to get it from an incandescent lamp in the first place.

It’s slightly different with xenon lamps. They have a similar color temperature right from the outset, which is why Osram talks about the “xenon look” when it comes to bluish halogen lamps. It’s all down to gas discharge technology. After all, xenon lamps are close relatives of neon tubes. By the way, the latter needed a lot of developing to get rid of the bluish tinge. A lot of people found it unpleasant. But I’m getting sidetracked.
Because high color temperatures are relatively easy to achieve in gas discharge lamps, Osram goes to the limit of 6,000 kelvin with the Xenarc® Cool Blue Intense xenon versions, depending on the type. By the way, they only reach these values after a burn-in time which can take up to 10 hours.
So, it’s possible to have so much blue – sorry, ECE white. It’s not necessary for good car lights though. Between 3,500 and 4,000 kelvin is ideal for the eye. And for these color temperatures there are plenty of good lamps. More blue is only a matter of personal taste.

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