Color Temperature Scale: Origin and Application

The Origin of the Kelvin Color Temperature Scale (If You Want to Geek Out)

Up until the invention of LED lighting, temperature was directly related to the type of color a light source would produce. Every man-made light source besides LED lighting required the production of heat in order to make light. If you remember from your high school science class, Kelvin is a unit measure of temperature (reminder: it was usually attached to how hot the sun was or some distant star).

A Kelvin color temperature scale works something like this: if you were to stand next to and look at a torch flame, you could feel its heat and see that it gives off a very intense blue light. In contrast, if you were to stand next to and look at a candle, you would see it gives off very little heat and produces a less intense yellow light. So that’s why a light bulb with a color temperature of 7,000K has a blue hue versus a 2,700K light bulb with more of an orange hue.

Helpful hint: Cool white and warm white does not directly relate to the actual Kelvin light scale. “Cool” refers to the icy blue hue that a higher color temperature produces and “warm” refers to the candlelight-yellow hue a lower color temperature produces.

Where Is the Light Going?

Are you looking to place this light in a living room, hallway, kitchen, or bedroom? The lightbulb’s placement may determine what color temperature you choose.

A lower color temperature or warmer light (2,700K- 3,000K) is less intense to our eyes, making this range the best color temperature for bathrooms, living rooms, family rooms, or bedrooms, where we want to promote relaxation. Research indicates that cooler, bluer light can disrupt the production of melatonin, a hormone that helps regulate sleep.

A higher color temperature or cooler light (5,500K-6,000K) is more intense and often works best in an office space, study room, or kitchen light color temperature. For spaces where you perform tasks like reading, cooking, or studying, a cooler color temperature is ideal as it provides brighter illumination and can reduce eye strain.

If you’re placing a light outdoors, the more intense cool white light may offend neighbors and confuse wildlife. However, you may also more easily get the attention of an onlooker with a cooler white. Warmer color temperatures are common in landscape lighting to create a relaxing, comfortable environment, while you might prefer cooler temperatures for security lights.

If you need lighting for horticulture, consider that certain indoor gardening systems use specific color temperatures to stimulate plant growth. Cooler color temperatures are typically used to promote vegetative growth, while warmer color temperatures are beneficial during the flowering stage.

What Type of Mood Do You Want?

Because warm whites carry a lower frequency than cool whites and are therefore less intense to our eyes, you can often set a cozy and more relaxing mood with a warm white light. If you’re needing to keep a more productive mood in the area you are lighting a cool white which has a higher frequency and is more intense to our eyes might give an added benefit.

Some common colors associated with the color temperature scale are:

Other Measurements of Light

If you’re trying to determine what light will work best for your situation, color temperature is not the only measurement to consider. Delivered lumens, wattage, and color rendering index are other measures you’ll want to look into to determine the best light for your needs.

Here is a brief description of each measurement and its function.

Lumens: The amount of visible light a source can produce. It will typically help you to know how bright a bulb will be. In this case, higher is brighter. Helpful Tip: Although many feel cool white lights are brighter than warm white lights, it is more a perception than a reality. Cool white has a higher wavelength frequency and therefore is more intense to our eyes making it appear brighter. However, If you compare a warm and cool white light that delivers the same amount of lumens they will both be as bright as the other, but produce different colors.

Wattage: The amount of watts, or units of power the light requires. This will help you to know how much energy you are consuming with the light you purchased. The higher the wattage used the more energy you consume.

Color Rendering Index (CRI): A measure of quality that helps to reveal a light source’s ability to show colors as they truly are. This measurement is different than color temperature because instead of determining what color the light will produce the CRI will determine how well colors will look under that light. Higher CRI ratings will produce better-quality light.