The invention of artificial light revolutionized society. It brought people indoors and extended working hours, night life and education far beyond sunset. Life as it is today would be impossible without light. Now, with the availability of new technologies, combined with a good understanding of how light influences human behavior, we are set for the next era of illumination. We spoke to Dieter Lang, Expert for Human Centric Lighting in the R&D of LEDVANCE. Dieter is also chair of the standards committee FNL 27 at the German Institute for Standardization DIN and chair of the Expert Team HCL at the lighting division of the German Industry Association ZVEI.

All living species on earth have developed under the rhythm of day and night. Some animals or plants have adapted to the night, but most are diurnal and are showing their maximum activity during the day. Also, humans have evolved as a day-active species and need daylight for their activity. Artificial light allows us to spend more and more time indoors and meanwhile we spend around 90% of our live apart from natural light. Often, we don’t have the light levels which our biological system needs to function well.

While plants for decoration in a room are usually placed close to the window to receive enough light, people often suffer from a lack of bright light.

We know that plants cannot see, but still need light. In the same way, also humans need light not only for vision, but also for their non-visual, biological system. Light has significant impact on performance, well-being and health of people. Light is synchronizing our day-night-rhythm with the natural course of day and night. Light supports us to be active, concentrated and performant during the day. But it needs to be bright and similar light daylight in order to achieve this. In the evening, when also the natural daylight gets darker and less blue, this helps to relax and to prepare the human body for a good sleep at night. So a warmer and darker artificial light is also the best choice for the evening.

What seems to be normal and natural is usually not available in our indoor environment. In our offices, schools, hospitals, wherever we are during the day, we usually find the same static lighting all the time – day and night. Our indoor lighting is very far away of what is natural and necessary for us.

Luckily the new LED technology and intelligent lighting systems are giving us the opportunity to get over this. And not only technology evolved to a point where a simulation of daylight also indoors is feasible. Our complete understanding of the human biology and of the effects of light has evolved to a point where we can transfer this new knowledge into lighting applications. Even standards are existing, which allow to transform scientific findings into practical applications. We have come to the point where the paradigm for lighting changes. From only enabling vision, we move to supporting human performance, well-being and health. This is a revolution in lighting which transforms illumination from a commodity to a health-relevant topic, comparable to good nutrition, sports activities and an in general healthy way of living.

The term Human Centric Lighting developed in 2010 and is intensively used as of 2013 to indicate that lighting needs to go beyond vision and energy saving. Light has to focus on human needs and to support all aspects of human living as far as light can do this. It puts people in the center of lighting design and is an abbreviated synonym for the need to include visual, biological and emotional aspects of light in the lighting design.

The potential of Human Centric Lighting has first been proven in nursing homes. The success and the improvement of the resident’s situation by better light which supports especially those who are no more able to leave the house, was so clear and impressive, that HCL solutions including daylight and artificial lighting have developed to a kind of standard in modern nursing homes.

This has been extended to many more application fields by different studies, which showed consistent results in various applications: from schools and hospitals, to offices, manufacturing sites and private homes. Each place where people spend their time indoors without sufficient daylight is a place for HCL. In hospitals for example, research has proven that illumination closer to natural lighting substantially supports care and recovery. It helps to restore sleep patterns in intensive care units and prevents depressions. In schools, pupils as well as teachers benefit from daylight-oriented illumination levels. They increase concentration and alertness, while lower light levels can support relaxation by creating a calm environment. And also in the working environment HCL helps employees to perform better and to do their job with success and without being too exhausted at the end of the day.

Such a dramatic change in our understanding and in the use of lighting requires some time to establish. You need more than a light switch on the wall. The light must be controlled by an intelligent system. It will take some years until this will be widespread in all offices, schools or other indoor environments where we spend our time. But everybody who had the chance to experience a modern HCL solution would never like to miss it again.