LED and colour quality

While LEDs do not have a full colour spectrum, we must pay special attention to its colour quality and colour rendering capabilities.

LEDs may contain less red wavelengths. This may cause poor rendering of red colours. It is possible to avoid this by using special materials when producing the diodes. Nevertheless, one must pay special attention to the LED’s Ra or colour rendition index, CRI.

When LEDs are produced, the production outcome is LEDs with many different colours or colour temperatures. The CIE’s colour diagram is used to create a binning structure, i.e. groups of diodes that share the same colour characteristics. The LED suppliers offer different bins to luminaire manufacturers. The fewer bins the higher cost.

Some binning systems relate to the human eye’s colour sensitivity via a model called MacAdam ellipses. The ellipses are mapped onto the binning structure in the colour diagram and their size corresponds to the LED’s colour tolerance. The size is measured in steps. The more steps, the bigger tolerance and the easier it is to spot a difference in colour. Generally, a 3-step ellipse is considered a good colour tolerance. Most Glamox luminaires comply with a 3-step tolerance.