What is Color Temperature and Why Does it Matter?

The idea that color has temperature might seem a bit like rocket science, but the concept has nothing to do with the supposed heat that a color gives off. Instead, color temperature measures the visual hue of a light source. Darker colors that appear “warmer” (sunsets, campfires, etc.) have a lower temperature, while those with a “cooler” look (daylight, HID lights, etc.) have higher temperatures.

We won’t dive too deeply into the scientific geekery behind color temperature.  A short and sweet explanation is color temperature starts with the concept of a “blackbody.” In the world of physics, this is an ideal theoretical object that absorbs all radiant energy (including light) and appears absolutely black. Think of a blackbody as a black metal sphere. As intense heat is applied to it, the color of that black sphere will change from different hues of black, red, orange, blue and white. The theoretical amount of heat required to get to those different colors is measured in Kelvin. And that is what gives us a color temperature chart.  

Why Should You Care?

So why does any of this matter? Color temperature wasn’t much of a factor in the dark days of halogen bulbs. The vast majority of halogen bulbs were available with color temperatures around 3,200K. For comparison, a sunset clocks in just below 3,000K. Driving around with a couple of old halogen headlights producing the same hue as a sunset might sound romantic, but it wasn’t the best for seeing where you were going.

LED headlights and replacement bulbs eliminated the irrelevance of color temperature with their unique ability to produce any color temperature. It suddenly became important to know precisely what hue of light you were getting across the color temperature spectrum. For example, those swapping to LED lighting for their homes can choose warmer or cooler temperatures depending on the look they want. It is important to match temperatures across multiple indoor lighting fixtures, too. But color temperature also matters a lot in automotive applications.

What is the Best Color Temperature?

Our eyes are calibrated for optimum vision during daylight, which has a color temperature between 5,500 and 6,500K. Light will start to appear more yellowish below that temperature (like halogen bulbs) and more blue or purple above it (like some annoying HID conversions). Ideally, if you are looking for replacement LED headlight bulbs or LED headlights, you want to match their color temperature to the peak performance range of your eyeballs. That is 5,500 to 6,500K, in case you already forgot.

However, there are some exceptions. Light with the color temperature of sunlight reflects much easier. This bouncing of light might not seem like a big deal until you get into inclement weather. All that white light reflects off of fog or falling snow and directly back to you, leading to glare and a loss of vision. Yellow LED fog lights might not operate in the ideal range of your eyeballs, but their color temperature of around 3,000K is a lot less reflective. The result is less glare and lights that can penetrate deeper into fog or snow without bouncing around for better vision. Dipping below yellow in the color temperature spectrum to amber is also an option but best suited for dust.

Lumens Absolutely Matter

If you have been paying attention, you might have noticed that yellow LED fog lights have a similar color temperature to halogen lights. But put both next to each other, and the yellow fog lights will seem much brighter. Why? Because they are. It is important to remember that color temperature and lumens are (mostly) separate from each other. Only at the extreme ends of the color temperature spectrum does it get harder to produce more lumens. Halogens and yellow LED fog lights might have similar temperatures, but the average LED fog light produces four times the amount of lumens as its halogen counterpart. LED bulbs will always be brighter than halogen, regardless of temperature.