• 17-10-2019

Nhiệt độ màu (K) & Chỉ số kết xuất màu (CRI) là gì

When purchasing new lights, you might have come across these terms on the specifications listed on the box. So, what are these exactly?

Do read on, and hope that you will have a better understanding of what they are and how it would aid you in purchasing for lights in the future.


*Colour Temperature [Kelvin] – (K)

*Colour Rendering Index [CRI] – (Ra)

Colour Temperature

Colour temperature is a measurement of colour produced by a light source, understanding this will help you in selecting a suitable colour temperature bulb for the selected purpose.

There are times when you might have come across terms such as warm light, cool white or day light, and by looking at it, you will have a general idea of the colour temperature the bulb will produced. But do you know, there is actually a range of colour temperature to denote these terms.

In simpler terms, different light source will emit a different glow of light, therefore these different colours are expressed in numbers and the numbers are known as colour temperature.

Take a look at the images below to understand more on the range of colour temperatures and the terms to different colour temperatures.

*Images for illustration purposes only

From the images above, you might be confused as to why do warmer colours have a lower colour temperature, whereas cooler colours have a higher colour temperature. Notice that the measurement for colour temperature is in – Kelvin (K), therefore the measurement of colour temperature is not correlated to the amount of heat it produces.

As colour temperature is subjective and versatile, therefore it’s possible to mix different colour temperature lights in a space, to create a different ambience.

*Below is an example on the usage of different colour temperature, do note that these are for references.

Colour Rendering Index – CRI

What exactly does CRI mean, and what does it measure?

Colour Rendering Index – (CRI), it measures the colour accuracy of a light source -light bulb- illuminating an object, compared to sunlight -reference point- illuminating on that object.

The index is measured from 0 – 100, with CRI 100 denoting that this light source has the ability to illuminate the colours of an object most accurately when comparing it under natural light.

The chart below shows the Colour Rendering Index and other bulbs’ CRI performance.

*Do remember to select a light that has a minimum rating of 70 CRI on your next purchase!

Many a times people might overlook this aspect when they are purchasing for a light, as they thought that selecting a high wattage and the right colour temperature is all they need. But they fail to realise that a high CRI actually changes the perception when viewing an object. A low CRI will make an object looks dull and boring, whereas a high CRI will make an object looks vibrant and appealing.

*Look at the image below for CRI illustration.

Does the apple on the left or right looks more appealing to you?

Have you ever wondered why does an object looks more vibrant and appealing during point of purchase, but the colour sort of changes when you brought it home? It’s not because the cashier swapped your product during checkout, it is due to the fact that they have installed higher CRI lights in the shop to increase the appeal of a product. These are all part of the buying experience that retailers would want consumers to experience.

High CRI is important for commercial purpose, as a high CRI has the ability to bring out the truest colour representation

Although it might seem that CRI might be more relevant for commercial purposes, but it’s also equally important for home use too. As a high CRI allows you to perceive objects in a positive manner and helps to elevate your mood.

Hope the article above will clear any doubts or questions you have on both colour temperature and colour rendering index. Although there are many other factors to consider, such as energy efficiency and the number of hours it will last.

Coupled with this new knowledge, you will be able to make an informed choice when purchasing your next light!