During the Design Week in London, I came across a studio of Lighting in Clerkenwell.
A lighting designer gave me an interesting leaf let of an interview which I want to report below:
Tell us about human centric lighting
Human centric lighting (HCL) is fast becoming a buzzword for any lighting product or design that uses a "tunable white" light source. LED technology has enable us to control a broad range of colour temperatures from very warm white light to daylight white light (sometimes referred to as " tuanble white"). It is not new to the world of lighting but is now much more attainable, hence its greater prominence recently.
But is it just a marketing term - what does it actually mean?
The " human" aspect of the term is the most important. Lighting (particulary artificial lighting) is, or should be, about humans and how we operate in the space, be it a hotel, workspace, home, factory, etc. As humans we should be the focus of any lighting design. So the human centric lighting term perhaps makes sense!
So what is human centric lighting?
Much has been talked about the benefits of artificial lighting mirror imaging our body clocks.
We humans are attuned to how daylight works- it raises in the morning and goes down at night and we then sleep whilst it's dark. Just like daylight, circadian rhytm is about intensity, colour, position, softness, direction and texture.
It is what shapes our world. To create internal lighting that mirror images this is an exciting prospect. However, there are some misconceptions; human centric lighting is not simply about producing a light fitting with tunable white LED's to enable the user to control between warm and daylight colour white light. There is much medical evidence and research to prove the benefits of different white lights- certainly true of the blue and of the spectrum for alertness, for example.
Is HCL only possible with LEDs?
No. In fact HCL has been around for over 10 years, it's just that LEDs make the control of the colour of white light and its level much simpler and more attainable. LEDs also come in a very broad range of colour temperatures which make it much easier to integrate into a luminaire.
How important are light levels?
In the workplace they are particularly important. The indoor office environment has a fraction of the light levels (illuminance measure in Lux) outside. Generally light outside has a range circa 3.000 Lux ( most dull English days!) to 10,000- plus in direct sunlight (once a year if you are lucky!). UK CIBSE lighting guides recommend between 350-500 Lux (500 being the industry standard) for a workplace. Energy consumption is often at the heart of trying to achieve the minimum requirement which could be argued as not very "human centric"!
Any do's and don'ts?
One important consideration when light planning is the scale of the space, - open - plan workplace offer a larger field of vision to a human than a segregated office room, for example. You cannot achieve good circadian efficiency with accent lighting.
Indirect lighting should be considered as part of the field of vision process.
The other is the direction that the light is going and what surface it will hit. Indirect light or ambient (the upper half of the room) has a positive biological effect in the lower half because it's comparable to cold white light from half because it's comparable to cold white light from outdoors; it actually enters the lower part of the retina where the most ganglian cells are found. When the sun sets, to have indirect cold white light would be inappropriate as it's not what happens outside.