The Kelvin scale (K) is often used to describe the colour ‘temperature’ of light in photographic and lighting contexts. A lower colour temperature will be ‘warmer’ with more red tones, and higher temperatures are ‘cooler’, with more blue tones. See our Colour Temperature Explained guide to find out which is right for you.
The Kelvin scale (named after the British scientist and engineer William Thomson, 1st Baron Kelvin) is a measure of temperature, starting at ‘absolute zero’, the coldest anything can be. The scale uses the same units as the more familiar ‘Celsius’ scale, so 0°C is 273K.
The colour temperature of daylight is generally accepted as 5600K. Relating this to light bulbs, a normal household incandescent bulb has a temperature of around 3000K, similar to halogens and ‘warm white’ LED light bulbs. ‘Cool white’ LED light bulbs are usually around 6000K.
Although our eyes are very good at adjusting to the colour temperature (unlike camera sensors and film), anything much above 6000K will look quite blue, ‘feel’ cold, and be unsuitable for normal domestic and commercial lighting.
While people are generally more comfortable with ‘warm white’ illumination, ‘cool white’ bulbs are ideal for accented lighting of objects and small areas.