Colour temperature (Kelvins) Bulbs used in households must meet certain quality requirements for light colour and object rendition. Regarding white light consumers can usually choose between the so-called warm white, the neutral white (day light) and the blue-white light bulbs (cold white). The colour of the light shall be determined by the colour temperature of the bulb expressed in Kelvins (on the packaging indicated by K). The warm white light is between 2600 and 3200 K, neutral white around 4000-4500K, and blue-white is within the range of 4500-6000 K.
Colour temperature and colour options – LED lighting is available in cold white (around 5000-8000K), neutral white (3900-4500K), warm white (2700-3500K), red, green, blue, yellow and purple.
"Cooler” light is more economical.
“Kelvin (K) is a unit of temperature. A temperature equal to 0 Kelvin is called an absolute zero temperature, while the Kelvin's temperature scale is an absolute temperature scale. The Kelvin's value is equal to the Celsius degree, but 0°C = 273.16. Also the colour of light or colour “temperature” shall be measured in Kelvin degrees and may vary from warm to cold. If the temperature expressed in Kelvin's degrees is low, such as 2700 K, the bulb emits a warm light that is relaxing and therefore more suitable for the home. The higher the temperature expressed in Kelvin, for example, more than 4000 K, the colder the light emitted by the bulb. Cold light is more suitable for the workplace.
Candle emits – 1930 K,
Sunrise and sunset emit - 1850 K,
Incandescent bulb emits 2700 – 3300 K,
Moonlight emits 4100 – 4150 K,
Daylight emits around 5000 K.
3. Light temperature
Light sources are characterized not only by the power, but also by the tone (colour). It is characterised (designated) by colour temperature.
Typical colour temperature of incandescent bulb - 700 K, halogen lamp - 3000 K.
Unlike incandescent lamps, LED lamps are produced with different colour temperatures, ranging from 2700 K to 10000 K. 2700 k – the indicator of warm light. 3000 k – neutral white light, between 4000 and 6000 K – cold light (daylight) and more than 6000 K – colour characterised by a bright light blue tone. Thus, LED lamps enable the use of different tones (colour) to illuminate different objects. It should be noted that, by decreasing light temperature, the output of LED bulb on 1W electric power will be decreased within 5% limit.