Although most lamps emit 'white' light, this can vary from a cosy 'warm white' to a cold or rather 'cool white', according to the 'colour temperature' of the lamp. Colour temperature is measured in degrees kelvin and denoted by a numerical figure followed by the letter 'k'. Somewhat confusingly, and in complete opposition to the celsius scale, lower values equate to warmer colours and vice versa, as can be seen in the chart below...

Colour Temperature Scale


The values in this scale apply to some of the more common colour temperatures found in modern lighting applications. Some bulbs are tied to a specific colour temperature because of how they work, such as incandescent bulbs that use heat to generate light and therefore naturally produce a warmer glow than other bulbs. Other technologies though - such as LED - can accommodate multiple colour temperatures, from warm white right through to daylight and beyond.

2700k - Extra Warm White/Warm White

Similar light to 'normal' incandescent bulbs, giving a warm, cosy feel.

3000k - Warm White

The colour of most halogen lamps. Appears slightly 'whiter' than ordinary incandescent lamps.

3500k - White

The standard colour for many fluorescent and compact fluorescent tubes.

4000k - Cool White

Gives a more clinical, high-tech feel.

6000k - Daylight

Fluorescent or compact fluorescent lamps simulating natural daylight.

6500k - Cool Daylight

Extremely 'white' light used in specialist daylight lamps.