In last weeks blog I discussed how LEDs light sources can vary hugely in their efficiency – simply some produce more light for the wattage that they use than others. However, that isn’t the only difference between LED and traditional light sources, such as halogen. By the nature of their manufacture LEDs vary from each other in a variety of ways but the one that provides the most noticeable effect to the human eye is their variety of differences in the colour of the white light that they produce. The human eye is extremely good in detecting colour differences and I have often heard people comment that they have seen LED light sources which cast a greenish or pinkish tone when they expected to get pure white light. Within the same production batch LEDs are often prone to quite wide differences. To help minimise the effects of the colour differences a sorting system was developed by the LED manufacturers. When the system is well run LED components are accurately divided into those of close colours resulting in batches of LEDs that have only the slightest deviations from each other. These batches are known as colour bins.
The amount of variation in the colour is expressed in MacAdam ellipses with the lower the number the harder it will be for the human eye to be able to tell the difference. Average quality LED lights will have a MacAdam ellipse figure of between 4 and 7 where it is quite likely that the difference will be noticeable. The colour temperature of lights or lamps with a figure of 1.5 MacAdam ellipses or lower will not be discernibly different for anyone older than their middle teens (due to the degradation of the eyes by that point!) and up to 2 MacAdam ellipses is considered to be very good.
So, when picking LED light fittings where you will have multiples of them in the same space look for and ask about the MacAdam ellipses. Generally, the higher quality manufacturers give this information out freely and the lower quality ones tend to be less forthcoming. I have waited days in the past for this information from certain manufacturers when I have been trying to show clients what changes when you go for lower priced products. You should bear this fact in mind when you are using numbers of the same fittings in close proximity, especially when they are set against a white background where the differences could be more prominent. Be aware that if all of your lights are from the same bin and it’s a bin that allows a wider range of difference these differences will not be considered as a reason for rejecting them.