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Colour Rendering Index

Confused with many lighting choices

What to expect when buying lighting?

Nowadays, lighting is more than just a tool that helps us exclude darkness and gloom during evenings. Proper lighting can enhance task performance, improve the appearance of an area, or have positive psychological effects on occupants.

Numerous factors shall be taken into consideration when buying quality lighting, e.g. energy efficiency, life expectancy, correlated colour temperature, durability etc. Colour Rendering Index is probably one of the most crucial of aspects of lighting to be looked at when purchasing any type of lighting. Nevertheless, very few customers actually happen to know what does it mean and why it should be taken into account.

This info page would emphasize the importance of colour rendering index and explain its significance in providing quality lighting that would meet both the functional and aesthetic needs.

What is Colour Rendering Index?

Colour rendering index (CRI) is a measure that shows us how well a light source makes the colour of an object appear to our vision (human eye) and how “realistically” (one could also say “naturally”) the light source makes different shades to reveal.

In other words, CRI defines the ability of a light source to identify colours, and is measured on a scale of 1 - 100. On this scale a rendering of 1 is monochromatic light, and a rendering of 100 is natural sunlight, so you can think of the scale as a measure of the quality of light produced by the source.

For example, have you ever stood under an old street light at night and wondered why the colour of a car or your clothes does not seem the same as it does during the day? Although the lamp used in the street light gives off a lot of light, the CRI is very low so the appearance of any colour is transformed.

How CRI is measured?

CRI is measured in scale from 0 to 100 where 100 represent the maximum value with the highest colour rendering ability. CRI itself is calculated from the differences in the chromaticities (also referred to as “colour appearance”) of eight CIE standard colour samples that have been illuminated by the light source under test and then again tested by a reference illuminant of the same Correlated Colour Temperature (CCT).

High CRI vs Low CRI

Majority of the light sources that are considered good at colour rendering has a CRI of 85 to 90, but light sources which have a CRI of 90 or higher are known as excellent and are the most appropriate for tasks that require the most accurate colour discriminations such as photography, neonatal care and cinematography. Low CRI values means that colours when illuminated by the light source, might appear in unnatural colours and will differ from the ones you would see during the daylight. Following is the comparison of colour rendering with different CRI values.

Colour Rendering Index Comparison

Comparison of colour rendering with different CRI values

Why is high CRI 90Ra important?

When thinking about the interior of workspace such as office, factory and classroom, it is known that lighting with high CRIs can promote concentration and higher productivity. At the same time, it improves retail sales, mental awareness as well as mood. Lighting does impact our moods and who would not want to have all the nice colours and details of our home and place for daily activities to appear as close to real colours as possible.