White light has different shades and while there is no general consensus, warm white light for LEDs has a value of 2500K-4000K on the color temperature scale, pure white 4000K-5000K and cold white 5000K-10.000K.
Warm white LEDs, as with all manufactured products, have material and process variations that yield products with corresponding variation in the shade of white light emitted. For example Nichia warm white LEDs just out of the production line can have a color temperature between 2580K and 4260K. If they would be directly integrated into strips or luminaries they will yield color inconsistent products that are generally unusable.
To overcome this problem, LEDs must be color sorted by the manufacturer with additional further sorting down the supply chain, if necessary.
Color sorted LEDs are grouped in batches known as "Chromaticity Bins". Nichia, as a LED manufacturer, groups white LEDs in many Bins, thus allowing very good control of the white light color of your project.
The Nichia Bins for new generation LEDs start with the letters "sm" follower by a series of numbers, where the frist two describe the color temperature (65 as in 6500K) while the last two narrow down the selection interval.
Nichia also offers color sorting in 3step, 5step and 7step MacAdam ellipses. While a detailed explanation of LED color sorting can be found here, we recommend that you choose the color sorting based on your project:
- General Lighting: 3step
- Ambient Lighting: 3step or 5step, where 5step could be more affordable
- Street and Christmas lighting: 7step
- Flashlights: 5step or 7step
Chromaticity Diagram of Nichia LEDs for
General Lighting - MacAdam