Color rendering index (CRI)

The color rendering index (CRI) tells you how true colours look under a given lamp. It is measured against a reference source of the same colour temperature, and the closer the score gets to 100, the less fabrics, timber and skin tones are distorted. Lumens describe how much light there is; CRI describes how good that light is.

Why CRI matters in interiors

A low-CRI fitting can make a room look flat and slightly grey. Food in a kitchen, skin in a bathroom mirror and products on a shop shelf all shift in colour. That is why high-CRI LEDs are a sensible default in homes, hotels and retail. The general Ra figure is an average of a handful of pastel test colours, so it is worth checking R9, the saturated red value, as well. It is what keeps wood and skin looking warm.

Renders versus the real room

In a render engine you set a light’s colour or Kelvin value, but there is no CRI slider; virtual light behaves like a perfect spectrum. The colours you approve on screen may therefore not survive a cheap fitting on site. Writing CRI into the lighting specification, alongside the visuals from an interior visualization project, keeps the finished room closer to the images.