Color Temperature Explained

Although people overlook it, they should always consider the difference between color temperatures. This is a very significant factor when you install new LED lighting fixtures.

It’s possible for the light emitted by two different light bulbs that produce the same number of lumens to be quite different. This is because they have different color temperatures. This includes LED fixtures. Color temperature makes up a big part of indoor and outdoor lighting. We are often asked what the best color temperature for warehouse projects using high bays, and outdoor parking lots using shoebox fixtures.

The difference is very significant, even on the biological level. Human brains are configured in such a way that they respond differently to certain light and colors.

The impact of color temperatures on a person’s behavior is notable. Warm-toned colors elicit feelings of calm and relaxation. Cool-toned colors elicit feelings of alertness and they boost productivity.

Understand the Lighting Spectrum

High-quality light comprises diverse kinds of light colors. One can spot this through the naked eye. For instance, you can easily see a multi-colored rainbow when the light is split by tiny water droplets that act as prisms.

Or you can simply make your own rainbow through a CD. All you need to do is to hold a CD in the light and its prismatic layer will begin to break up the light into its fundamental colors.

The visible colors of light are Violet, Indigo, Blue, Green, Yellow, Orange, and Red. It is shortened to VIBGYOR. In the VIBGYOR spectrum, the least energetic light is red and the most energetic one is violet. However, there are various other forms of light on the spectrum, which one cannot see.

This includes infrared light and ultraviolet light. As their terms suggest, ultraviolet comes after violet light on the spectrum and infrared comes before red.

So, LED lamps are designed specially to offer a good quality of light and color temperatures. These lights create a complete spectrum of light featuring all the visible light colors. Humans cannot see UV or infrared lights as these lights are not in the visible spectrum. Thus, these lights are entirely useless to human eyes.

Even so, both UV and Infrared lights may damage paintings and art objects in your home. Also, UV light is even considered dangerous for genetic material. As compared to LEDs, other kinds of bulbs, such as Incandescent lamps, produce 95% of the light output in the invisible light range. Thus, this makes such light bulbs highly energy inefficient.


How Do Humans See Warm and Cool Colors?

What we see as white light contains all the diverse light colors in equal proportions. So, when white light strikes an object, most light colors get absorbed and only some are reflected.

Thus, the color of an object is determined by the light color it reflects. It is quite important that a lighting source needs to emit light with all the light colors in it. As a result, we will be able to perceive the color accurately.

If a lighting fixture does not bring out a specific light color, things of that color will be invisible in the natural shade. That’s why sodium lamps are terrible at replicating accurate colors.

This is because sodium light is primarily made of yellow light, which falls into the narrow-spectrum light. Thus, when you place a thing of a color other than yellow under a sodium light, it reflects all the different yellow shades.

This offers nearly every object under these lighting sources a sickly hue. On the other hand, LED lights produce only natural colors. This is because the light comprises a perfect spread of all colors. Plus, there is a well-balanced light.

All 2700 6500

Color Rendering Index and Light Spectrum

Color Rendering Index or CRI measures how precisely light from a lighting source is going to reproduce colors. Although there is a difference between CRI and color temperature, these two terms are correlated with each other.

To know more about CRI, head to our CRI article. For now, it is just significant to understand that CRI refers to a measurement of the light quality emitted through a lamp.

On the other hand, a higher CRI does not always correlate with a perfect color temperature.

Incandescent light is the light source that has an ideal CRI. This light serves a 100 index as the spectrum offers all the color spectrum wavelengths. Incandescent lights can be compared to sunlight, which is a natural lighting source having a 100 CRI.

However, LED systems and products are different altogether. If you look at pictures produced using an LED projector, the produced colors are far superior compared to older technology. So, LEDs are a perfect lighting source, which can be used in warehouses, schools, and factories.

Visual tests clearly show that the CRI definition must be revised. Scientists ask observers to give ratings to color schemes. These ratings are used for defining the CRI of a light bulb under various lighting sources.

The comparisons of LEDs with bulbs having a higher CRI are quite surprising. The observers have an impression of equal light quality despite LED lights featuring a lower CRI than other bulbs, like incandescent.

Light Spectrum and Lighting Devices

The reason behind a perceived CRI is color temperature. An incandescent lamp, that produces warm yellow light, does contain all the light colors. However, these colors are not present in equal proportions. An incandescent lamp lacks violet, blue, and green lights.

Thus, when you place violet, blue, or green objects under the light of these bulbs, the colors get distorted. By contrast, LEDs produce a well-balanced, complete light spectrum. Here, the lights reproduce the natural colors of things.

  • Sodium lamps feature a very poor CRI of around 25
  • Mercury lamps have a CRI of 50, and
  • HIDs feature a CRI of 72.
  • The CRI of LEDs and CFLs may vary with a light color however, it generally lies between 75 and 85.

The Color Rendering Index or CRI of a lighting source is comparable across different sources that function at the same temperature. LEDs work at a very low temperature when compared to incandescent bulbs.

That’s why a CRI of 85 underestimates the performance of LEDs. So, there are plans to take another look at the CRI standard for reflecting the actual reality of the lighting world.

Color Temperature

As mentioned above, the ‘color temperature’ term defines the temperature of an object through which it emits light. These objects are modeled through a black body radiator. When you increase the temperature of this black body, it begins to emit visible colors in a continuous light spectrum.

So, the filament of an incandescent bulb featuring 60 Watts heats up to around 3000°F. Thus, the bulb emits light with a 3000K color temperature.

Most of our artificial lighting sources do not produce light by heating up materials until they glow, such as incandescent lamps. Rather than producing a continuous light spectrum, these lights create an assortment of color emission lines.

Kelvin Color Temperature Scale Chart

What Does Correlated Color Temperature Mean?

LED lighting sources employ a detailed chart for assigning a correlated color temperature (CCT) rather than using the heated filament’s color for determining the color temperature. One can calculate CCT based on the black body radiator’s correlated color temperature. Check out the chart below to see how this works!

The curved, black, line is called the “Black Body Curve.” This curve represents the object’s color temperature, which is heated until it releases light. The lines that intersect the black body curve show the point range on the chart. So, this will result in a particular color temperature.

For instance, A Metal Halide bulb having the Coordinates: 

A=0.396, B=0.402 shows that the bulb has a 3800K Color Temperature (signified by the red “A”)

Cct Chart

Importance of Color Temperature

Color temperature is particularly important in photography and desktop publishing. Differences in color temperature can result in variations in color rendering.

In home and office task lighting, the color temperature of lights is important as different colors of light have different psychological impacts and are designated as ‘warm’ or ‘cool’. Ironically, the so-called ‘warm lights’ have a lower ‘Color Temperature’ while the ‘cool lights’ have a higher ‘Color Temperature’. Warm and cool thus refers not to the color temperature but to the psychological attributes of lighting. The light from wood-burning fires and incandescent bulbs is yellowish in color.

The human mind, conditioned by thousands of years of social evolution, accepts yellowish light as warm and inviting. On the other hand, day white light is associated with cleanliness and efficiency – as in hospitals. It is also dependent on cultural and regional backgrounds as people from countries nearer to the equator prefer cold white light sources to warm white lights.

The choice of light color temperature is governed by the look you wish to create in an area. Lights of different color temperatures are described by their similarity to known sources or with typical adjectives. The color temperature chart below can help you choose the right lamp for your needs.

Color Kelvin Temperature  Characteristics and Examples Describing the Light Best Uses and Locations
2700-3200K Incandescent bulbs, yellowish light accentuates wooden objects and skin tones Warm, relaxing, friendly, intimate, inviting Reception areas, homes, hotels, boutiques
4000-4500K Similar to early AM sunlight, automobile Xenon headlights Natural tone, clean and neat Offices, School Lights, Outdoor Lighting, Hospitals, Commercial Lighting
5500-6000K Flashlights, Daylight, Metal Halide Natural outdoor, crisp light, brightly lit, slightly blue tint Shops, Factories, Printing Businesses, WarehousesParking Lots, Outdoor Lighting
7000-7500K Superior contrast, but not flattering for the skin. Bluish light, bright light, cool light, cool white Used for applications that need good color rendition and high light intensity. Used in museums, art galleries, and showcases for jewelry & precious stones.

Lower color temperature intensity makes the light appear warmer that goes on to be redder as the temperature goes down further. By contrast, light will appear bluer and cooler at higher temperatures.

Fixtures for both residential and commercial lighting systems have color temperatures (kelvin scale) that range from 2000-6000K with 2700K and 3500K being the most popular ones.

This means that people prefer warmer lights in residential applications. By contrast, there is a preference for cooler lights with industrial lighting and commercial lighting applications.

What Lights Do I Need – Warm or Cool?

The warm color lights are usually good for residential spaces as they make the ambiance appear more welcoming and comforting. Marking a contrast, cooler lights work better for industrial and commercial spaces.

This is because the cooler lights help the workers feel better and be more productive by relaxing them. However, what makes this difference in light suitability occur between the residential and commercial spaces? The answer to this lies in the biological nature of lights that we mentioned above.

The cooler color temperature fixtures produce brighter white light that causes the bodies exposed to it to release serotonin. These neurotransmitters alert the senses of people. This is similar to the way one feels more awakened when exposed to sunlight and how one finds it difficult to sleep after having stared at a screen continuously for a while.

On the other hand, warmer lights cause the exposed bodies to release melatonin. This hormone regulates the circadian rhythm or the natural body cycle of sleep-wake to help people feel relaxed and sleepy.

This explains why warm white light fixtures are chosen for residential spaces and areas like living rooms and bedrooms specifically. These lights cast a relaxing and comforting warm light effect on people and help them rest better. The places in homes that do better with cool fixtures include bathrooms and kitchens.

At the same time, bathrooms are fitted with even cooler-toned light fixtures. This increased difference in contrasting and color rendering works better for spaces like bathrooms than the common cool and neutral light fixtures that serve other places better.

The usage of warm lights is not restricted to residential spaces only. These fixtures are still fitted in various commercial spaces like reception areas, lobbies, hotels, restaurants, etc. The primary idea behind this is that these lights can be used in any commercial space that needs to make its visitors feel relaxed and comfortable.

On the other hand, cooler lights serve the purposes of high contrast and boosted productivity better. The major use of cool LED lights is for office buildings as the bluer-toned lights help to increase the workers’ productivity. However, there are many other particular spaces where cool lights become more essential than just important. Such places include workshops and factory floors that need brighter lighting.


A Comparison of the LEDs with High Pressure Sodium and Metal Halides

Well, this isn’t even a fair competition. LED lights have distinctive technology built in that makes them produce better quality light. By comparison, other lights perform best to their limited capabilities. High-pressure sodium lights have CRI between 20-40 and a color temperature of 2300K. These factors determine the warmth or yellow hue of the light produced.

Metal halides do better than high-pressure sodium but are found lacking when compared to LEDs. Their CRI is better than high-pressure sodium, but color temperature is almost similar. However, it is also a fact that the high CRI doesn’t remain constant throughout the life of lights. After you purchase the lights, the light quality will begin to degrade slowly with time.

Lastly, LEDs provide the best results as they let you customize both color temperature and CRI. You can choose to either buy LEDs with a pre-determined CRI or ones with remotely controllable CRI.


The Most Popular LED Color Temperatures

HID Bulbs

5000K Color Temperature

The lights belonging to this color temperature range produce a whitish-blue color and are mostly used for accurate color representation in commercial and industrial areas where it is required.

The lights belonging to this color temperature range produce a whitish-blue color. They are typically used to accurately represent colors in commercial and industrial areas where it’s needed.

4000K Color Temperature

The lights belonging to this color temperature range produce a neutral white color and are one of the most profoundly and variously used lights. This color temperature gives a balanced tone between yellow and blue to the LED lights.

This gives two benefits to the exposed bodies- an alertness span that lasts for a longer time and a reduction of the risk of eye strain from blue lights. These lights are ideal for commercial areas such as offices, retail stores, and hallways.

3000K Color Temperature

The lights belonging to this color temperature range produce a yellowish-white color. The slight warmth of these lights gives a cozy and relaxing effect to the spaces that make them ideal for usage in commercial spaces that require a comforting and welcoming ambiance. They are typically used in areas like spas, lobbies, etc.

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About the Author

Cory Peterson is Director of Sales & Marketing at LED Lighting Supply where he focuses on improving customer experience and revenue operations. Cory writes about commercial & industrial lighting, along with topics important to contractors and facility managers. In his free time, Cory enjoys traveling, snorkeling, exercise and cooking.

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