August 22, 2016

Human Centric Lighting



Scientists and lighting industry are gradually realising how light affects the human body and mind.

Some argue that with ‘human centric lighting’ we try to challenge nature. Indeed, nature has made an day / night cycle, a perfect balance suiting our need for wake and rest

Our eyes are perfectly suited to the ever changing natural light natural light, not so much to many artificial light sources.

Even natural light impacts our mood and sometimes wellbeing, just think of dark overcast or foggy autumn afternoons or bright sunshine at the beach or in the mountains.

From the days mankind first used artificial light to light up the night or their cave we humans have been living what might be called an ‘unnatural’ life. However, we want artificial light to fulfil our needs whether at work, at home or going out, so we need to utilise the best technology available to make artificial lighting practical, affordable and suitable to our physiological (and psychological) needs.

We are ‘experimenting’ for quite some time with ‘mood lighting’ however we have some more work to do understanding how light affects our bodies. We made quite large steps forward in recent time, also there is much more awareness in society.

Used properly Human Centric Lighting (HCL) should meet our ‘natural human’ needs i.e. it should be applied carefully and thoughtfully, always putting our physiological needs first.

Accepting that the real human-centric ‘healthful’ lighting is light emitted from the sun and stars in the night sky how then do we do use HCL effectively?

Many issues have to be addressed. Light / dark cycles to recreate day and night for travellers and shift workers, for people who are indoors for prolonged amount of time, e.g. in hospitals.

Light quality to reduce flicker and a light spectrum close to the Quantian locus.

Indoor lighting suiting the task or the mood.

A lot of work has been done on HCL and health, mood, productivity and general wellbeing. But there is a lot of controversy and the science is unclear.. For example, some say that blue light should be avoided as it might trigger cancer, while others say blue light is uplifting and can be used to increase focus and productivity and should only be avoided 2 hours before bedtime.

Colour temperature has just became more widely understood, consumers just start to understand how to translate the old measurement for brightness i.e. the wattage of a lamp into the “new” (and more correct) measurement of luminous flux (in lumen, lm), but we still ignore very important factors such as the Spectral Power Distribution (SPD) or cromacity, which describes how the human eye perceives the light. Light of the same correlated colour temperature (CCT) might appear more greenish or reddish depending on the lamp.

At this stage there is a lacking of understanding of the details, and most lighting people are lacking physiological and psychological knowledge and most doctors lack an understanding of (solid state) lighting. No wonder, they all graduated from schools with bad fluorescent lighting.