Ask a person what is the best quality of light and the answer is normally: daylight. However, without us realising, daylight is not a fixed and defined kind of light. It is changing continuously; varying over the course of a day, but also changed by other conditions (for example clouds). Both the intensity and the colour change over time. It starts with an orange/pink low light level in the morning, going to a bright blue-ish colour in the afternoon, back to orange and then to very low moonlight levels at night.

Healthcare appears to be the most suitable candidate for HCL. For one, people are there 24-hours per day. Furthermore, research shows that tailored lighting can improve measures of sleep, depression and agitation. HCL would cover a 24-hour period with stimulating light in the morning, ‘winding down’ lighting in the afternoon and relaxing, cosy light levels in the evening. At night, ‘dark’ amber lighting (without blue elements) would accommodate sleep.

The effect in education and offices is less pronounced, however the emotional aspect is more important. It can stimulate activity levels at the right times of day, especially when natural lighting is limited. During lunch time hours lighting can be dimmed for energy saving purposes. In educational settings and meeting rooms in offices it is perceived very helpful if scenes can be selected to support a certain task or activity. For example 4 scenes of lighting that stimulate: activity, focussing, relaxing and attention.

In other applications the effects are less pronounced.

For example, it is not very effective in night shifts (24/7 industries) because you can only control the lighting in less than half of the person’s day. Nevertheless, some effects have been demonstrated. Having said that, the emotional aspects of Human Centric Lighting are more subjective and can apply to any environment. In the end, the ‘quality of light’ is relevant to all situations.