Correlated Color Temperature(CCT)
Correlated Color Temperature(CCT) is a measure of the color of a light source relative to a black body at a particular temperature expressed in degrees Kelvin (K). It characterizes how the white light looks. For instance, if the light goes more blueish, it would have a “cool” temperature, and if it’s more reddish, it would be “warm” in temperature.
Warm white has a lower Kelvin than cool white. Typically, warm white could be considered as below 3500K, natural white between 3600K to 5000K and cool white above 5000K.
The color temperature of LED is mainly depend on the ingredients of the phosphor. Compared to conventional lamps like incandescent, halogen, LED has a weak point that the degradation of phosphor’s performance will affect the color temperature, and then lead to the color drift on various degree. This happens when the phosphor is working under the high temperature for a long term, usually after 5000-10000 hours.
To solve the problem, LED manufacturers should take measures (such as adopting the low current driver, bigger size LED chip or thermoelectric separation technology, etc ) to decrease the operation temperature of the LED chip, or use the better performance phosphor(for example, intematix).
To achieve high lighting quality need to consider both color temperature and illuminance. In environments with low illumination intensity, light with low color temperature makes people pleasant and comfortable, on the contrary high color temperature makes people feel dizzy, depressive and cold; however, in a high illuminance occasion, light with low color temperature makes people feel stuffy and dull, while high color temperature makes people feel refreshed and concentrated.