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What Is CCT and CRI?

Oct. 08, 2021
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Getian CRI 95+

Getian CRI 95+

It's all about quality lighting! Or is it? One thing is for sure ...... If so, then there are 3 things you need to know: CRI, CCT and foot-candle. These are the three most relevant measures of high or low-quality light. Because they are essential for evaluation when choosing an LED, CRI stands for Colour Rendering Index (CRI) and CCT stands for Correlated Colour Temperature (referred to as the colour temperature of many lamps). Footcandles are a measure that describes the total amount of light that hits a target area. Let's talk about all three measures at once so you can better understand how they describe the quality of light and how they can help you save energy on your lighting solutions.

 

Colour Rendering Index (CRI).

CRI is a measure of the ability of light to show the actual colour of an object compared to an ideal light source (natural light). A high CRI is usually the desired characteristic (of course, this depends on the desired application). If your goal is to illuminate a scene so that the colours all appear naturally (for example, this is often an important requirement in cinematography), then you need a high CRI led module


Conversely, if you are lighting an underground tunnel and you don't particularly care whether the shape is black and white or colour, CRI may not be as important. However, we tend to think that a high-quality colour rendering is beneficial in almost all cases. Importantly, there is a detailed explanation in the article "What CRI Means?" - you can click to learn more.


High CRI 95

High CRI 95

What is CCT?

The relevant colour temperature is a measure of the colour temperature of light that is used as a substitute for light that is not close to a blackbody emitter (i.e., they emit light by a process other than thermal radiation). Fluorescent lamps and LED lamps (light-emitting diodes) both fall into this category and are therefore evaluated using CCT. 


The relevant colour temperature is the norm used to describe the dominant colour of non-blackbody emitters so that they can be accurately compared and contrasted with those light emitters that approximate blackbody radiation (e.g. incandescent bulbs). The lower end of the scale (~2000K) is usually referred to as 'warm' (usually red and yellow), while the higher end of the scale (5000K+) is usually referred to as 'cool' (usually white) to light blue), the same as the colour temperature scale.

 

Footcandles.

A footcandle is a measure that describes the amount of light reaching a specified surface area, rather than the total amount of light from a light source (luminous flux). Footcandles are measured in lumens per square foot, not simply lumens (as in the case of luminous flux). Simply measuring lumens is deceptive because the light that illuminates extraneous areas (e.g. ceilings) is not used efficiently.


Furthermore, luminous flux does not indicate how well the light beam is focused. Different optics and housings will focus more or less light than other optics, resulting in more or less illuminated target areas from the same type of light and the same amount of power. What you really care about is the amount of light that actually illuminates the required surface area. From the user's point of view, therefore, footcandles are more important than total luminous flux. In addition to unit differences, some light from a light source will never reach the desired target point (i.e., the light is not 100% efficient). 


A certain amount of light is always lost due to inefficiencies in light absorption, reflection and/or dissipation, etc. Foot-candle takes this into account, whereas luminous flux does not. So forget about luminous flux for now and focus on foot candles as they are the more relevant lighting metric in the real world. If you want to get more information about the high stability COB chip price, please contact us.