What is Kelvin? A Complete Guide of the Kelvin Scale

What is Kelvin?

Kelvin is a unit of measurement that is used to describe colour temperature. The temperature at which an object produces light is known as its color temperature. The higher the colour temperature, the bluer the light will appear. The lower the colour temperature, the redder the light will appear.

For example, a candle has a colour temperature of around 1800K, whereas the sun has a colour temperature of about 5800K.

One advantage of using Kelvin to measure colour temperature is that it allows for direct comparison between different objects. For instance, it is easy to see that the sun emits much more blue light than a candle.

However, it is essential to note that Kelvin is not an absolute scale, and there is no definitive cutoff between blue and red light. Instead, it is simply a way of understanding how different light colours relate to each other in terms of temperature.

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Color Temperature Applications

What is color temperature?

Colour temperature is a measure of how warm or cool a light appears. It is usually measured in Kelvin (K). Colour temperature has a significant influence on lighting. A space dedicated to intricate activities will require a precise colour temperature than ambient lighting.

color temperature overview 1900K to 4500K

2700K – Warm White

2700K - Warm White is the color temperature to use if you want to create a cozy and welcoming environment.

This color temperature is most commonly used in homes, restaurants, and hotels because of its warm and inviting glow – similar to sunset or candlelight.

Ideal color temperature for creating a friendly atmosphere, whether you're entertaining guests or just unwinding at home.

3000K – Soft White

Soft white light creates a warm and inviting atmosphere while providing enough clarity to complete tasks.

This color temperature is standard in bathrooms and kitchen areas, as it creates a welcoming space without being too harsh on the eyes.

Soft white light bulbs are also an excellent choice for bedrooms and living rooms, providing a cozy and relaxing ambiance.

The perfect option whether you're looking to create a cheerful space or a calming retreat.

3500K – Neutral White

Neutral white light falls in the middle of the spectrum, with a color temperature of around 3500K.

This type of light is reminiscent of the natural light that occurs during the middle of the day.

It is bright enough to promote alertness and focused activities, making it well-suited for office spaces and retail stores.

Light is warm and easy on the eyes and won't cause eye strain or fatigue.

For a versatile light bulb, you can use it in various settings, and neutral white is a great option.

4100K – Cool White

Cool white light is typically associated with clinical settings like hospitals and laboratories.

The color temperature of 4100K is perfect for these places because it creates a very bright light.

Perfect for staff when working with patients or conducting experiments.

Cool white light is also often used in office settings. Many people find that it helps them to concentrate and makes them feel more alert.

This type of light is becoming increasingly popular in modern workplaces and other specific environments.

5000K – Bright White

5000K light fixtures provide the intense, white light needed to ensure clarity and accuracy.

This color temperature creates a stark contrast that makes it easy to distinguish between different colors and objects.

5000K light fixtures are ideal for locations where precision is essential.

In addition to their utility, 5000K light fixtures also have a modern look that can add style to any setting. Whether you need bright white light for functional or aesthetic purposes, 5000K light fixtures are an excellent option.

6500K – Daylight

All plants primarily receive their illumination from the sun, and the 6500K color temperature for daylight is similar to actual sunshine.

This color temperature has a clear blue tone and is commonly used for indoor farming, greenhouses, and other agricultural purposes.

Plants grown under 6500K daylight bulbs are more vigorous and yield higher than those grown under different lighting conditions.

This colour temperature is ideal for human eyesight, providing a bright and clear light that helps to reduce eye fatigue.

6500K – Daylight bulbs are an excellent choice for any environment where plants are grown or people spend extended periods indoors.

What is CRI?

A flashlight's CRI, or color rendering index, measures an artificial light source's ability to render colours accurately compared to natural light. Simply put, it is a way of quantifying how "true" a light source is.

The higher the CRI, the more vibrant and true-to-life colors will appear under that light.

When shopping for a flashlight, pay attention to the CRI rating to ensure that you can see clearly in all lighting situations. A high-quality flashlight with a high CRI rating is an essential tool for any well-equipped home.

Most LED flashlights have a CRI of 80 or higher, which is considered excellent. However, some LED flashlight on the market with a CRI is as low as 50. These lights should be avoided, as they can produce an unnatural-looking light that can make it difficult to see clearly.

CRI is invisible until you shine it on an object

A common misconception about CRI is that it is only visible when you shine it on an object. The reason for this is that CRI is a measure of the amount of light that is reflected from an object. An object will reflect some of the light back to your eyes after being illuminated. Your eyes reflect a certain quantity of light, which influences how much color you see.

The higher the CRI, the more light is reflected in your eyes, and the more vibrant the colours appear.

How is CRI measured?

A light source's CRI rating indicates how correctly it can depict colors. The CRI is calculated by comparing the colors of an object under a given light to the colors of the same thing under a "perfect" or reference light source.

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The higher the CRI, the better the colors will appear under that light.

The reference source is usually natural sunlight. To calculate the CRI, various colour samples are placed under the tested light, and their colours are compared to the colours of the same pieces under the reference light. The CRI is then expressed as a number on a scale from 0 to 100, with 100 being perfect colour rendering.

Because different objects reflect different colours, eight different colour samples are used in the calculation, each representing another type of object. These eight samples are combined to produce an overall CRI score. While a CRI of 100 is considered perfect, most practical lighting applications only require a CRI of 80 or above.

This is because our eyes are not very sensitive to small changes in colour, so a light source with a CRI of 80 will appear to render colours quite accurately to most people. Therefore, when choosing a light source for your home or office, it is not necessary to select one with a CRI of 100; any light with a CRI of 80 or above will work well for most purposes.

Maximum CRI Value: 100

The CRI, or Color Rendering Index of a flashlight, is a score that measures the light's ability to render colors accurately.

The CRI is expressed as a number between 0 and 100, with 100 being the best possible score. A CRI of 50 or above is generally considered to be good.

A higher CRI score means that the light can better show off the true colors of objects. A lower score indicates that colors may appear muted or distorted.

While most people think sunlight is the best source of light for color rendering, certain types of artificial lighting can also produce high CRI scores. For example, LED flashlights are often praised for making sharp, transparent colors.

When choosing a light source for tasks such as reading or photography, it is crucial to consider the CRI to ensure that you will render colors accurately.

A light source with a CRI of 80 will produce colors closer to natural sunlight than a light source with a CRI of 60. Generally, higher-quality light sources will have a higher CRI, making them ideal for applications where color accuracy is essential.

What are Kelvin, color temperature, and CRI?