What does the introduction of TM-30-15 mean for the lighting industry?

The introduction of TM-30-15 is helping to create a stronger, credible dialogue between manufacturers and designers, ensuring lighting specifications are performing as expected. Here, Fred Bass, director of Neonlite and owner of Megaman, explains why. 

The lighting industry is continuing to evolve its benchmarking methods with the relatively new introduction of TM-30-15, seeking to displace Colour Rendering Index (CRI) as the industry standard for measuring colour rendition. This method is gaining increasing focus within the lighting community as the criteria within TM-30-15 goes above and beyond the traditional CRI. 

The CIE have just published a research report for a new colour fidelity index CIE 224:2017 which follows a very similar methodology, however the CIE plan to go further with perception related colour quality measures and this report does not yet replace the existing CRI.

When using the traditional CRI system, the only way a designer can be sure they get the colour quality they want, is by obtaining multiple manufacturers’ lamps and testing them in situ. This is because product data sheets cannot guarantee a high colour rendering accuracy because the current CRI system allows for too many inaccuracies.

The CRI system was developed over 40 years ago and by today’s standards uses out-dated tools and formulae. Even before the solid-state lighting revolution, the industry faced issues when trying to compare the colour of different light sources – and the introduction of LEDs has only exacerbated this. 

The general CRI, known as R_a, tends to be inaccurate because it only uses fidelity (fidelity index – closeness to a reference) to measure colour, the method uses just 14 Colour Evaluation Samples (CES) and then only averages 8 of them, which is why R_a values can be the same while the eye perceives colours rendered differently. R_a uses only pastel shades so R₉, the saturated red CES, is often used in addition to give an index on how saturated the light is.

TM-30-15 on the other hand goes much further than traditional CRI, comprised of three main components: 

• R_f – a fidelity index that is similar to the commonly used CRI
• R_g – a gamut index that provides information about saturation
• Colour vector graphic – a graphical representation of hue and saturation relative to a reference source

TM-30-15 uses 99 Colour Evaluation Samples, compared to CRI’s 14, to measure colour fidelity, which uses better colour space, spectral uniformity and covers a broader range of colours. 

More and more projects, across a wide range of industries, are specifying LEDS with higher Ra as colour quality and rendering grows in importance. However, simply specifying a high CRI LED may not create the desired affect. 

Using the TM-30 method of measuring brings in additional information and designing and specifying decisions become much easier and more controlled. It is advisable to partner with suppliers who can provide a high level of service and support to ensure the LEDs chosen are absolutely fit for purpose.

Furthermore, as new research shows that saturation has a significant affect on our perception of colour rendition and light levels, it is a significant improvement that TM-30-15 includes a saturation index (Rg).

TM-30-15 provides a broader, more detailed understanding of colour rendering between different light sources. This represents a more comprehensive way to compare light sources like for like, but also allows manufactures the ideal opportunity to embrace a form of ‘best practice’ when it comes to light measurement.