Colour Rendering Index (CRI)


The Colour Rendering Index, or as it is more commonly known CRI represents how faithful the light sources can reveal colour or colours of the illuminated objects compared to the same colours when revealed by an ideal source of lighting or natural daylight (sun light). CRI is represented by a number value that can go up to 100 and it is usually easier to get higher CRI values with lower values of correlated colour temperature. CRI values are usually achieved by measuring 14 “R” values that go from R1 to R14 and each one represents a specific colour. There is also the Ra value that is calculated through the average value between the CRI values of 8 “R’s” and also has a top value of 100.

CRI and Ra information is critical when choosing luminaires for spaces where colour assumes the main roll on what is being illuminated, such as: apparel stores, art galleries, fashion accessories, and especially on fruit stores and butcher’s stores where a good CRI will reveal the freshness of the products. Furthermore, on the daily life, high CRI lighting provides higher visual comfort, protecting vision, which results in a better and higher life quality in which concerns the eye health and also helps to reduce stress.


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Low-pressure sodium 1800 15
Clear mercury-vapor 6410 17
High-pressure sodium 2100 24
Warm-white fluorescent 2940 51
Natural-white fluorescent 4230 64
Ceramic discharge metal-halide lamp 5400 96
Incandescent/halogen bulb 2700 90

Midday Sunlight