LED colour temperature basics

Light varies in nature and the perceived colour of an object depends on the light source that hits it.

The human brain can "correct" for these colour changes very well, but the film or CCD/CMOS sensors we use cannot do this.

If an object burns, first the flame is red, then it turns orange as the temperature rises, then it turns white and finally, blue appears.

The Scottish mathematician and physicist lord kelvin was the first to discover the close relationship between heat and colour in 1848 and left the world with the great concept of "absolute zero" (-273.15 degrees Celsius). This led to the creation of the Kelvin temperature scale. This is the theoretical basis of how we talk about colour temperature today.

The Kelvin scale expresses temperature in units of K (abbreviation for kelvin). Here, for example, the lower the value the more "red" the flame is, and the higher the value the more "blue" it is. Red and blue are not colours of light per se, but simply indicate that there is more red or blue in the spectrum.

Here is a look at a common standard in the Kelvin scale: "absolute zero" is expressed in Kelvin as 0 K, which corresponds to -273.15 degrees Celsius (or -459 degrees Fahrenheit), at which temperature the thermal activity of a substance ceases completely.

The bluer the light, the higher the colour temperature; the redder the light, the lower the colour temperature. The colour of light varies depending on the colour temperature of the light source. Colour temperature below 3300K has a stable atmosphere and a warm feeling; colour temperature in 3000 - 5000K is the middle colour temperature, with a cool feeling; colour temperature above 5000K has a cold feeling. Different light colours from different light sources make up the best environment.

Preferences in colour temperature vary from person to person and are related to the scenery we see on a daily basis. For example, in areas close to the equator, the average colour temperature that people see on a daily basis is 11,000K (8,000K (dusk) to 17,000K (midday)), so a higher colour temperature is preferred (it looks more realistic). Conversely, people in higher latitudes (average colour temperature around 6000K) prefer lower colour temperatures (5600K or 6500K), which means that if you use a high colour temperature TV to show an Arctic landscape, it will look blue; conversely if you use a low colour temperature TV to see a subtropical landscape, you will feel a bit reddish.

How is the colour temperature of a TV or display defined? As the average colour temperature of the Chinese landscape is between 8000K and 9500K throughout the year, TV programmes are produced with the viewer's colour temperature of 9300K for photography. However, the usual colour temperature in Europe and America differs from ours and is produced with an average colour temperature of about 6000K throughout the year as a reference, so when we watch those foreign films, we will find that 5600K to 6500K is the most suitable for viewing.

At 6500K, blue-eyed people see white, while black-eyed people see yellow.