Human Centric Lighting
What is Human Centric Lighting?- An illuminating talk by Professor Warren Julian
Human Centric Lighting Design is an old Concept, given that our circadian clock runs on a 24 hour cycle. But It was difficult to maintain the circadian entrainment effectively with traditional lights. With the advent of LED, having expanded colour capabilities and seamless control on colour changes and dimming, a lot of research is underway to make our visual system respond more effectively to the light stimulus. Dynamic Tunable LED, varying the spectrum from 6500K to 2700K, has increased the circadian effectiveness of the human system. Increasing daytime alertness and nighttime sleep can be addressed in near future by acutely synchronizing the circadian system of human beings with proper doses of red and blue light. A brilliant presentation on Human Centric Lighting was made at Hong Kong International Lighting Fair 2017 by Professor Warren Julian of Sydney University. I have tried to reproduce the original talk as much as possible save for some very minor modifications. Hope you will enjoy reading it. So crisp and lucid that even a person with no knowledge on light and vision can gain rich insights into what Human Centric Lighting is?
Hong Kong International Lighting Fair (Autumn Edition) 2017
Putting People First —
the Revolution of Human-centric Lighting
27th October 2017
Emeritus Professor Warren Julian,University of Sydney
its origins and implications
The Talk >>>>
> What lighting is about
› We see with our eyes (part of our brain)
› Two visual systems plus one for our body clock
› We are really daytime people
› This is what you really see
› Revealing contrast
› What human-centric lighting is
› Concluding remarks
What lighting is about
“flow” of light — not just downwards; revealing (sky)light and directional (sun)light; sky and sun have all λ and do not flicker
We see with our eyes (part of our brain)
Two visual systems plus one for our body clock
We don’t see all colours equally
We are really daytime people
We walked out of the forest
and onto plains to become a
›We are a daytime predator
with very good vision
›Our eyes are designed for
›We cannot see at night
›We are frightened of the
›We used to go to sleep after dark
This is what you really see
This is due to Retinal Eccentricity.
is due to the differing pattern of response to light stimulation across the retina due to different conditions and the different densities and ratio of and across the surface.
Cone sensitivity varies over the in the presence of a uniform photopic background and sensitivity falls off in the from a sharp peak, then declines more gradually toward the periphery
We must detect contrast to find edges
What human-centric lighting is
Philips, for example, gives a definition on its Lighting University Resource Browser:
Human-centric lighting is lighting devoted to enhancing
vision, wellbeing, and performance individually or in
This suggests there are three
enhancing human vision,
Lighting has always been human-centric
In fact, it cannot be other than human-centric because the photometric units (lumen, lux, etc) are all based on the human (only) response to light.
› Lighting standards are predicated on providing good seeing conditions,which encompasses “enhancing vision”, “performance”, through a sufficiency of light and the minimisation of performance reducing effects such as glare and unwanted reflections, and “wellbeing” by lighting the environment as well as the tasks using appropriate light in terms of CCT and CRI.
› Competent Lighting Designers were aware of the circadian role of lighting before the recent discovery of the physiological mechanisms involved.
That meaningless word “wellbeing”
“Wellbeing”, enthusiastically embraced by the alternative medicine and cosmetics industries, has become a byword for many in the lighting industry.
› Good lighting can produce a feeling of wellbeing by good design and by reducing unwanted effects such as glare.
› However, greatest impediments to wellbeing in most workplaces are:
- is poor task design , eg, allowing insufficient time to complete the task’s visual component
- by asking people to work when their circadian cycle is calling for rest or sleep
- by not providing distance views that allow the intraocular muscles to relax,
- by not providing views of the outside that are both visually stimulating and allow the perception of the passage of time.
› Superficial electric lighting colour changes and other control tricks probably exacerbate these problems, rather than ameliorating them.