The colour rendering index (CRI) indicates how well the colours of an illuminated object are reproduced under an artificial light source. It is measured on a scale that goes from 0 to 100 where 0 is the lowest level of colour accuracy and 100 is the highest. From a physiological point of view, daylight is the best source of light owing to its complete colour spectrum. Therefore, lighting fixtures with a high colour rendering index will increase people’s sense of well-being and comfort and are especially necessary for environments where faithful colour rendering is required.