What is a Macadam ellipse?
A macadam ellipse is defined as a region on a chromaticity diagram which contains all colours, which have no discernible difference to the average human eye, from the colour at the centre of the ellipse. The contour of the ellipse therefore represents the ‘just noticeable’ differences of chromaticity or colour visually seen. The greater the number of Macadam Ellipses, the greater the visual difference of colour coming from the light source.
Why is this important?
Whilst this may have had no major impact on traditional lighting, the Macadam Ellipse is highly important within the LED lighting industry, and is used to measure colour precision and the consistency of the light produced by LED chips. Simply explained, it ensures that the colour output (and subsequent changes of that output over time) are controlled to maximise colour consistency throughout the lifetime of the product.
In practical terms it means is that two identical products installed side by side should produce the same colour light output if using the same LED chipset, with the colour variance over time also following the same curve to ensure that even as a product dims, the colours will still match.
Why this matters to you
When a light is produced with a single Macadam Ellipse it will have no visual difference, two to three steps is good and widely used for commercial applications, and lower end products will have four to eight ellipses and potential colour differences.
When choosing your LED product it’s important to be sure that the quality of the product is consistent, especially if buying in volume. This is even more important when relating to light colour or ‘Kelvin Temperature’, as you do not want visual differences in the light emitted in a single space. Think of an office with three or four shades of white or cream and you will clearly see why this is important. Asking how many Macadam Ellipses a product has is a very simple way to identify how much colour difference you are likely to see in your space when lit, and also a very good check of the quality of the LEDs used to produce that product. Remember, good lighting manufacturer should always be able to advise you of the number of Ellipses your product should go through.