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Kelvin colour temperature explained

Author: Glenn Harper
Published: November 12, 2013

Colour temperature is a relatively new consideration in household lighting. Forty years ago, a bulb was just a bulb. The amount of watts was the only real decision to be made when replacing bulbs.
Modern lighting, however, has brought more choice with it. The colour temperature scale is a way of measuring all types of lighting technology, both old and new.

Colour temperature theory

During the 19th Century, British physician William Thompson (Lord Kelvin) devised the Kelvin temperature scale. During his research he heated a block of carbon, which began to glow red, then yellow, and finally produced a bright blue-white light.
The path of these changing colours is the essence of the Kelvin scale because each colour occurs at a specific temperature. For example, the filament of an incandescent bulb produces a yellow light at a temperature of 2700 kelvin (2700 K).
The one thing to remember is that a higher kelvin colour temperature equals to a cooler bluer looking light. Lower colour temperatures mean a warmer light.

Kelvin colour temperature scale

Correlated colour temperature (CCT)

In an incandescent or halogen light bulb, kelvin temperature describes both the colour of the light and the actual temperature of the filament. Because LED’s and fluorescents do not use heat to create light, their colour temperature is estimated in relation to the colour of the light. This is called ‘correlated colour temperature’ (CCT).

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Many people choose a welcoming warm white light for their home exterior. The dimmable Vega LED Wall Light emits a 3000K light and looks fantastic by the front door.

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For home protection, the 6500K daylight Deltech 10W LED Floodlight delivers a crisp, bright light, giving it extra impact as a security light.

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A warm and welcoming light is ideal for the hallway. This is also a common place to find pictures and paintings. A warm-light fitting such as the 2700K Goya 460 LED Picture Light will emphasise the reds in a picture. However, the cooler 4000K Goya 365 Picture Light will complement bluer tones.

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Cooler lights are a good choice for the kitchen as they promote alertness.
Under-cabinet lights such as the 6400K Eterna LED Linkable Striplight are a fine choice for the work surfaces. This fitting is linkable with five others, making it ideal for long worktops. Alternatively, Endon’s Surface Mounted LED Strips are another choice of cool under-cabinet lighting.

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Warmer lights are more suited to bathroom relaxation. They also flatter skin tones and make us look healthier. However, some prefer the brighter, crisper look of a cool white light.
The Fireguard LED6 Dimmable Spotlight is available in warm or cool options, and some models can be dimmed for perfect mood lighting.

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In the bedroom, a cosy warm white light is usually desirable. Reading lights are popular bedroom fittings, usually with a warm white bulb. The Fuse LED Reading Light has a 3000K output, and its long LED lifespan ensures years of maintenance-free use.

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In a living room or dining room you’ll usually want a warm, relaxing quality of light. The iconic Aperture Shade, from Luminosity, is a stunning non-electric lighting solution, greatly complemented by a warm white bulb.

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A kitchen diner or breakfast bar might benefit from a cooler light, which will help shake off any sleepiness ready for the day ahead. The stylish Loft Quad Spotlight Bar uses GU10 spotlights, which are easily obtainable in a choice of colour temperatures.

For a more in depth look into colour temperature click here.

If you are looking for more great information? Try our Lighting Ideas section.