Colour Temperature

Colour temperature is a characteristic of visible light and is a very important consideration for lighting applications. Colour temperature is normally expressed in the unit of absolute temperature, the kelvin, having the unit symbol K.

Colour temperature is used to indicate the warmth or coolness of a light source. Colour temperatures over 5000K are called Cool colours (blueish white), while lower colour temperatures (2700–3500 K) are called Warm colours (yellowish white through red).

In general, Cool light is best suited for visual tasks because it produces higher contrast than Warm light. Warm light is preferred for living spaces because it is more flattering to skin tones and clothing. A colour temperature of 2700–3600 K is generally recommended for most indoor general and task lighting applications. Colour temperature is not an indicator of lamp heat.

The following is a general guide to selecting LED lamps in consideration of colour temperature (K):

• 2700K  >  Homes (Living rooms, halls, bedrooms), Restaurants, Hotels (lobbies, corridors, bedrooms), Boutiques
• 3000K  >  Offices, Work areas, Retail stores, Outdoor lighting, Bathrooms
• 4100K  >  Showrooms, Display areas, Office areas
• 5000K  >  Jewellers, Hospitals, Museums
• 5600K  >  When outdoor/daylight simulation is required

Though Colour temperature and Colour Rendering Index (CRI) and are related, they do not address the same properties with respect to the colour performance of a lamp. Colour temperature is an indication of the colour appearance of the light source and the light emitted from it. CRI is concerned with how effectively the light from a lamp renders colours in various objects and materials. When comparing the CRI specification for two different lamps, both must have the same colour temperature in order for the comparison to be meaningful.