Colour rendering and why it’s important to understand!

Since the 1960’s we have evaluated the colour of light, and until only recently in 2015 the only measure to achieve this was using the Colour Rendering Index (CRI).
Today’s leading lighting designers and consultants are using the far improved tool referred to as TM30-15, and here’s a brief overview to explain.

Why do we need to know a colour rendering?
To see an object’s true colour is essential in many sectors such as within beauty, art, medical and even some retail applications. Understanding colour rendering and implementing the correct design will also deliver a far enhanced experience within an artificially lit space. It’s well known that humans need sunshine, so using the best colour rendering possible from an artificial light source can have many benefits from improving mood, productivity, boosting sales and even promoting mobility.

Brief overview of the Colour Rendering Index.
The measurement called ‘CRI’ only uses 8 sample colours to achieve an Ra rating, the Ra rating allows us to interpret how close an artificial light source represents the surface colour of an object when compared to natural sunlight.
Natural Sunlight is 100. Monochromatic light is 1.
To give context to this, most of today’s artificial light sources will have a CRI of 80 or 85 as commonly used in most commercial buildings. The lower the number the poorer the colour rendering.
An example of poor colour rendering would be Sodium lamps used in street lighting pre LED. Sodium lamps commonly had a CRI of 60. These lamps would wash an orange hue over all objects, so if you didn’t know that the grass really is green on the side of the road, you could be forgiven for not being sure when looking at it from under a Sodium light source.

Why was a new method developed?
We know that there are many more colours in the spectrum visible to the human eye than just 8. Therefore the CRI is considered to now be outdated and not informative enough to provide lighting design professionals and their clients the detail they need to deliver design excellence and the many benefits that a well-lit area delivers.
If we use only an 8 sample set of colours, via the CRI method, to try and describe a colour rendering means the reproduction of an objects’ visual appearance could greatly vary under an LED light source versus the trueness of natural daylight.

Brief overview of TM30-15.
Tm30-15 is the new and by far best method to assess colour rendering and quantifies colour fidelity (Rf) across 99 colour samples opposed to CRI’s very limited 8 colours.
It also includes the Gamut index (Rg), which represents the average saturation shift of the source when compared to the referenced illuminant. An Rg of over 100 is saturated, under 100 desaturated. Sunlight is 100.

TM30-15 in application:
A critical application for having the best colouring rendering possible from an artificial light source, thus the benefit of utilising the TM30-15 method, would be lighting artwork in a museum.
To fully appreciate its beauty, we need to see the colours as the artist intended.
Another example is a recent project undertaken where we lit a luxury department store which offers premium textiles and natural materials, such as stone, marble and wood. Using the TM30-15 method maximized the vividness and trueness of colour and also highlighted textures. In turn this greatly enhanced the appeal and client interest, as we used a light source that was capable of achieving this and importantly could provide proven test data through the TM30-15 measurement.