Colour temperature is, in its simplest form, is a way of describing the appearance of light, from warm to cool white. Typically, we measure this on the Kelvin scale between 1000 and 10,000, where the higher the colour temperature the colder the colours, with the warmer, more orangey, colours being lower on the scale (demonstrated below).
Generally speaking, the most common colour temperatures for residential and commercial use are between 2000 and 6500K.
LEDs and Colour Temperature
In their early days, LEDs were criticised for being too blue, giving off a cool colour temperature which people used to the warm colour of incandescent light bulbs. As technology has improved, we are now able to achieve all colour temperatures from LEDs, making them a perfect, low running cost, alternative to earlier lamps.
Even more recently, LEDs have been used in retail outlets as their colour rendering (the quality of artificial light compared to sunlight) has improved to the point where clothing and other produce look the same under this lighting as they do natural light.
How Colour Temperature Affects Us
Your circadian rhythm is your body’s internal clock, the thing that makes you sleep and wake when we do. As humans, we are most sensitive to yellow light, but our circadian rhythms are triggered by blue and ultraviolet light. Working as a zeitgeber (an external time keeper), these shorter wavelengths of light are what trigger our brain to be active, keeping us awake and alert. By modulating the amount of blue light in our environment, we can help people sleep and wake relax and be alert.
Therefore, with this knowledge, we can use light to help recovery times from illness and jetlag be reduced by moderating the levels of different hues of light.
A study conducted in a school in Sweden found that appropriate lighting helped the children concentrate better and, therefore, learn more effectively. This worked as it reduced the amount of Melatonin produced by the brain, which is also the chemical which is responsible for Seasonal Affective Disorder (SAD).