CCT stands for Correlated Colour Temperature and indicates the colour of white light. It is measured in units called Kelvin, which is denoted by the letter K. This parameter determines whether light gives a 'warm' yellow to orange impression or a 'cold' white to bluish impression. Low values, for example 3200 K, correspond to the warm light of a conventional incandescent lamp or a sunset. Conversely, high values, such as 5600 K, are closer to the colour of daylight. The main use of CCT in photo lights is the ability to adapt the colour of the artificial light to the surrounding environment. This makes it easy to match the light from the lamp with the natural daylight coming through the window or with other artificial sources in the room. Proper adjustment avoids unwanted colour shifts, where for example part of the scene would be yellowish and part bluish. In addition to matching lights, CCT also allows creative work with color to create a specific mood, for example to simulate warm evening light even during the day.