With a new technology comes new ways of measuring the colour temperature. Discover how LED is performing in comparison to other light sources.To the right you can see color reproduction of an LED compared to other light sources.

A colourful light source?

LED renders colors better in some parts of the color spectrum
Neither the colour temperature nor colour rendering of an LED is exactly the same as a traditional light source. The existing instruments and processes for measuring were developed for traditional light sources and aren’t suitable for LEDs.

The CIE is currently researching and developing new ways to conduct these measurements. While the Colour Convention Temperature may appear the same on different datasheets, the actual light experienced can differ between manufacturers, so it is important to pay consideration to this when choosing your LED solutions. Colour rendering is closely tied to the spectral distributions, the diagrams to the right show typical distributions for daylight, tungsten, T5, CDM and LED. Using spectral distributions, which colours will be rendered properly and any issues that may arise can be predicted.

Bin coding
When reading about colour rendering of LEDs, you may also have read about bins. Bin coding is simply a method for describing the specifications of an LED. The code consist of four parts: the flux rating, tint, VF (forward voltage) and colour. LEDs with similar wavelengths or colour temperatures are put into different bins. These are used to determine the quality of colour consistency between different LEDs.

The colour consistency of LEDs cannot be solely expressed through the colour temperature (kelvin). The colour quality of a 3000k LED, for instance, may vary depending on which bin it belongs to. An LED from bin 7C2 is more yellow than one from bin 7D1, which is more pinkish. Within the spectrum of a 3000k LED, the different bins move from a more gold/orange appearance, through to a more green and pink colour as demonstrated in the chart opposite. These fluctuations of colour highlight the importance of paying close attention to an LEDs bin and its specification.

Manufacturers are currently addressing some of the issues associated with colour bins, with particular reference to warm and neutral white, to make it easier to identify and specify the LEDs. This is particularly important for retail lighting where high colour consistency is required and where there should be little or no difference in colours between the LEDs being either installed or replaced. ♦