Correlated Colour Temperature (CCT)

The Correlated Colour Temperature (CCT) is a measurement of light’s colour in Kelvin (K) degrees. Most lights fall in a spectrum between 2,700K and 6,500K and there are many different definitions of colour temperature used in the lighting industry, some are even contradicting. At LEDCITY, we define outputs of 2600K to 3700K as “warm white” (more yellow / red), 3700K to 5000K as “neutral white”, and 5000K to 8300K as “cool white” or “daylight” (more blue). Studies have shown that light colour affects our daily sleep cycles and mood. Cooler colours promote wakefulness and productivity, while warmer colours tend to promote relaxation.

A tip is to stick to just one colour throughout an open area, because mixing of colour temperatures can be distracting to the eyes.

Colour Rendering Index (CRI)

The Colour Rendering Index (CRI or also denoted as Ra) is a measure of light’s ability to properly render colour (ranges from 0 to 100 - the highest possible score). Colour rendering is important especially for commercial applications in order to reveal the true vivid colours of products, artwork and architectural elements that are of interest.

The following table shows how to use CRI number of a light to find out its ability to properly represent colours:

Ra = 90 - 100   Excellent
Ra = 80 - 90   Good
Ra = 60 - 80   Moderate
Ra < 60   Poor