Colouring your thoughts

There’s a lot of talk about colour rendering and colour temperature, and it seems mostly about what the truth applied to LED.

Should it be R using the 8 sample scale (R8), or R using the 14 colour scale (some call this R14)? Doesn’t Ra of 100 compare to daylight, or is it tungsten? Does LED even tell the truth with colour rendering and isn’t there a better method?

Listen to all the hype, even as an expert and it all gets a little confusing. Then add colour temperature and efficiency and well, we might as all well retire down the bar for a glass of Rioja until we can reach a conclusion.

But there is a lot of talk about little differences. In the LED race to get better colour, we have perhaps forgotten the eyes ability to see, or the brains ability to interpret, both of which are more about perception than absolute measures.

In the race for the right colour temperature, we have certainly forgotten comfort and are as yet discovering the ability of blue light to affect not only the human sleep-wake cycle, but the effects on our many less powerful companions on the planet (flora and fauna).

Truth is the research is not joined up as yet as to the effect of artificial light on our companion species, but you we do know there is an effect. Given that blue and UV do control the lives of so many species, we’d do well to limit light pollution, reduce colour temperature outdoors, or even better switch off or dim when light is simply not needed. This is not asking the world. In lumen output terms 5700K to 4000K is less than 5% and less than 4lm/W different. You could easily make that up by part night dimming, choosing the right optic, or installing correctly for the application.

As to colour rendering, I thought about checking the colour rendering of my day-lit office, with and without artificial light. After all the messages in the market I truly wanted to find a significant difference in my working conditions. But here I met a problem. Admittedly I was sat under lighting by Thorn and Zumtobel brands, so I know the designs have been thought through and executed well. True to form my spectral analysis proved three things. Zumtobel achieved over Ra 90 on both scales. Thorn claiming Ra 80 achieved more like 85 on R8 and 80 on the R14 scale, just what we claimed. But then the shocker, the surprise about all these conversations, all these disagreements…

…the daylight component is only R90 (R86).

Daylight Spectrum Image
the spectrum of light measures through standard coated office glass

Admittedly that’s through the glass but perhaps we’ve got the discussion around the wrong way. Let’s not talk just about colour rendering, or which scale is correct. Let’s not talk of colour temperature or whether it’s relevant compared to efficiency. Like all light sources, choose a good one to do great job. Let’s instead talk spectrum, how complete it is, or in some cases how incomplete it should be and what’s appropriate in the application, both for us and our partners on the planet.

By maclighter

A Chartered Engineer in Lighting, though trained in mechanical, with 30 years lighting design, technical, manufacture and marketing experience. A trusted mentor, designer, emergency and DIALux trainer, speaker and past president of the Society of Light and Lighting. Get in touch if I can help you out.