Light sources and their colour rendition

Our surroundings are shown perfectly by daylight, incandescent an halogen lighting. Since the development of artificial lighting which produces light in a synthetic way and with a discontinuous spectrum, there were differences in the colour rendition.

The colour rendering index (CRI, Ra) is a quantitative measure of the ability of a light source to reveal the colours of various objects faithfully in comparison with an ideal or natural light source. The value of a particular light source is between 0 and 100Ra of which 100Ra is the most ideal colour rendition.

Colour temperature

The colour of the light itself, the colour temperature of the light source, inlfuences also the colour rendition as well as the perception of light. Light is often designated as cool or warm.

The gradation of light could be compared to a heated iron rod whose temperature is known. Heated iron becomes an orange red (warm) colour. The more the iron is heated, the more it becomes a white colour (and so a cooler) impression.

It is a known fact which colour the iron rod becomes when heated to a certain temperature. This gradation is also applied to the radiation of a light source. The colour of the light is expressed in Kelvin (K) and it is called the colour temperature. It is distinguished in the following categories:

• 2500-2800 K extra warm white
• 2800-3500 K warm white
• 3500-5000 K neutral white
• >5000 K cool white

The colour temperature of the light has nothing to do with the temperature of the light source, but only with the colour of the light itself.

Showroom Lightworld

Would you like to experience how light works? Visit our showroom Lightworld in Venlo, The Netherlands. Different light sources are shown and differences are shown clearly!