Color temperature of lights – what does it mean?

Lighting color temperature
What is the difference between cool white, warm white, and daylight color temperatures?

What color is white?

By color temperature I’m not talking about color changing lights.

Yes, you can choose from a wide variety of LED lights that change colors from red, green, blue to anything you like with an app on your smartphone or a small remote control.

Color changing lights can be useful tools for interior design, setting the mood, setting visual alerts (with the appropriate automation routines), or just fun to play with.

But there’s another aspect to adjustable lighting that is much more important – the white color temperature.

Understanding the color temperature scale and what it means is important whether you have smart or dumb bulbs, a great lighting automation system, or even just plain ordinary lights.

The color temperature of lights

This can get into a lot of physics of color temperature which can be fascinating, but also quite confusing or just plain boring. So please pardon me if I simplify and keep to the basics.

Everyday lights in our home may seem to be white, but they actually have a color tint.

Light can be generated in different ways. The most common technology has been heating a small tungsten wire until it gets so hot it glows and gives off light.

The incandescent bulb has been a mainstay of lighting for many years. The light it produces has a yellowish/amber tone.

The quality of light from the common fluorescent tube isn’t that good as it gives off a greenish tone. That’s why these lights are often used in garages, closets, and other locations in the home.

The modern LED light is brighter, energy efficient, and much more compact. Common LED lights have a blueish tone.

Scientific measure of light colors

Unless you look carefully, all of these kinds of light still seem white. Our eyes and brain are very forgiving and adjust to the ambient light under most conditions.

To make it easier to measure and compare the color variation and color shades of lights, scientists have a measurement scale for the color temperature of lights using units in Kelvin.

The “degrees K” of a light tells you exactly what color tint a white light actually products.

Color temperature “cheat sheet”

This is all very confusing so here’s how I simplify things:

Forget about it being called “color temperature”. For us normal consumers, it has nothing to do with temperature as we know it in heating or cooling systems.

It’s really just a color tone/color cast scale using weirdly large numbers labelled as “K values”, but it’s just a way to compare.

In a futile attempt to make this consumer friendly, the lighting industry has created meaningless words for the most common color tone settings.

If you look at a light fixture, LED, or light bulb, you’ll probably see terms like warm white, natural white, cool white, daylight. It’s all very confusing.

Each of these terms corresponds to a color tone value. Warm white is 3000K, natural white is 3500K, cool white is 4000K, and daylight is 5000K.

Why they can’t just say yellow(ish), white, or blue(ish) is beyond me!

But unfortunately, it’s not that simple. These are only approximate – there is no official agreed upon standard. Some lighting manufacturers may call their 4500K lights cool white while others may squeeze their 4500K fixtures into the daylight category.

The easiest way to think about color temperature values is to consider three main categories:

At the lower end of the scale, warm white has a strong orange and yellow tone. This is the traditional incandescent lamp.

In the middle of the scale, lights have more of a neutral/white color without any other tone.

At the upper end of the scale, lights have a slight blueish tone and give the feeling of being outside in bright daylight.

First generation LED lights were mostly in the 3000K (natural or cool white) temperature range, but are also available in the 5000K (daylight) variety.

The golden rule

When choosing light fixture with built-in LED lights or LED bulbs for ceiling cans or tabletop lamps, follow the golden rule:

Standardize on a single color temperature. Don’t mix different color temperatures in the same kind of fixture.

Mixing different color temperatures looks bad and hurts your eyes.

Since each manufacturer names their lights differently, rely only on the numerical K score (2500K, 2700K, 3000K, 4500K, etc.) to compare color temperature and not the descriptive words.

The simplest approach is to buy all the lights from the same manufacturer, if possible. Be aware that LEDs are constantly changing so you have to read the packages carefully to match light output (Lumens) and color temperature (K values).

Choosing the right color temperature

There is no right choice for color temperature but there are some standard recommendations.

Experts say to choose the color temperature based upon the primary use for the light.

For relaxing at home, especially during the evening, warm lighting (2500K to 2700K) is often preferred. The yellow and orange tone is pleasing and soothing to the eyes.

For task lighting – working at a desk, studying, or other concentrated efforts, daylight (5000K) lighting is recommended.

For general use under different conditions, mid-range color (3000K), as you might expect, is commonly chosen as it has a white / neutral color tone.

Robert

Automation technologist and problem solver

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