CORRELATED COLOR TEMPERATURE AND KELVIN
The CCT (Correlated Color Temperature) represents the color of white light. White light can be warm like candlelight or cool like fluorescent or an overcast day and many colors in-between. LED light sources use correlated color temperature to measure the color of the white light, based on the theory of a Black-Body Radiator. In simple terms, it measures what color of white light is created when a black metal object, like a horse-shoe is heated up to a specific Kelvin temperature. LEDs are assigned a correlated color temperature (CCT). For whites measured by CCT, based on the black-body theory, blue occurs at higher temperatures (6500K), while red occurs at lower temperatures (1600K).
Interesting facts about Correlated Color Temperatures:
1. The human eye can see the difference between warmer color temperatures easier than the difference between cooler color temperatures. This difference is called “Just Noticeable Difference” (JND) and, according to scientists, we can discern the difference in warmer color temperatures by 100K and in cooler temperatures by 500K. This is why Diode LED offers many in-stock color temperature options between 2000K and 4200K, but less off-the-shelf options above 4200K.
2. Binning specifications at the manufacturer can greatly influence the actual CCT of an LED chip.. Binning is the process where LEDs are tested and sorted according to several measurements, including Correlated Color Temperature. During production, LEDs will vary, even within the same batch. The differences between each LED can be significant and therefore LEDs are tested, sorted and delivered to the market in subclasses or groups called bins. Diode LED uses tight binning specifications so that when we offer 3000K, the variance of CCT between any LED chip is under the JND range identified above. Tighter binning is more expensive because not all of the LEDs manufactured are chosen for use in a lighting product.
3. The form factor can also change the CCT. For example, waterproof strip light has a coating that if not carefully overseen by the manufacturer can greatly change the CCT and light output of a product.
Reference--DiodeLED (Elemental LED, Inc.)