The power of light to change your world for good
Light Notes banner

Blushing, infra-red, LEDucation and PoE

The science of blushing and seeing (infra-) red…

This week was April Fool’s Day, the moment for pranks and practical jokes.

Social pressure – good or bad – triggers an involuntary autonomic response – increased core body temperature and heart rate which in turn leads to subtle shifts in blood flow to the face – a blush. Visible signs of a blush, or increase in blood flow to different parts of the face become evident approximately 15–20 s after the onset of the embarrassing incident. Blood is redirected from functionally significant regions of the face (eye socket and nose) to socially significant zones (the cheeks and forehead).

We know that the quality of light, particularly in the red part of the spectrum is critical to identifying these honest signals. That’s why choosing light sources with a high Colour Rendering Index, or the more sophisticated measure known as TM30/R9 is so important in settings where communication counts.

But this fascinating study used infra-red imaging to trace shifts in facial colour in conversations that were serious, social or included a compliment – Seeing a Blush on the Visible and Invisible Spectrum: A Functional Thermal Infrared Imaging Study.

Although these infra-red wavelengths are considered ‘invisible’ (fall outside the ‘visible’ range, or sensitivities of your rods and cones), it turns out that under some circumstances, your cones are not fooled.

This mechanism is known as ‘two-photon’ photoreception: two 1000nm photons hit a photoreceptor in rapid succession, their combined energies combining to activate a short wavelength cone at 500nm. That in turn triggers a red signal for your brain – Human infrared vision is triggered by two-photon chromophore isomerizationThis was first discovered back in 2014 but now scientists are using this double-dose effect for new diagnostic imaging techniques even be able to restore visual function using gold nano-rods tuned to respond to near infra-red light – Restoring light sensitivity using tunable near-infrared sensors.


LEDucation 2024 19-20 March,  New York

Fascinated by the contrast with Light+Building in Frankfurt.

Originally a simple table-top display in the Hilton Midtown Ballroom for New York’s local lighting scene, that same tired ballroom now crams in 10,000 visitors, 470 exhibitors in just two days.

Luckily the brilliant education programme has its own dedicated space.

The tight ‘table-top’ format forces a ruthless focus on ‘pile it high’ product display at the expense of concept, context and culture.

Few innovations on show but three themes I noted: biophilic-inspired materials and forms, some tunable and full-spectrum offers, modular systems and miniaturisation. 

But the clear blue water I saw between Frankfurt and New York was in the controls. The American market is traditionally driven by basic 1-10 dimming, limiting scope for dynamic, let alone ‘circadian’ protocols.  But smart, intelligent, or intuitive’ design and Power of Ethernet were hot topics in the (excellent) education programme. It will be interesting to see where the New World goes next.



PoE – fad or future?

PoE was making waves at Light and Building Frankfurt and LEDucation in New York.

But what is it and why should a lighting professional care?

LEDs can – and should – do more than switch on and off or dim if we want to harness the immense ecological and human benefits of this technology and create multi-sensory, flexible and adaptive environments where we can all thrive.

That means more sophisticated controls and integration with other building management systems  – occupancy, ventilation, temperature and air quality, security and IT as well as shading and daylight control.

That’s where PoE comes in.

LEDs run on direct current and need so little of it that the thin ethernet cables originally engineered to carry data can not only control the lights, they can power them too.

The bottom line…

  1. Reduced embodied carbon and installation cost – no need for a separate AC power cable
  2. Reduced energy use – no need for transformers or drivers that lose up to 20% of the input
  3. Reduced electromagnetic field interference with other sensitive equipment and systems generated by alternating current
  4. Integration and control in real time – the ethernet cable operates as a two-way bridge


What’s not to like?

  1. Underpowered for some applications – e.g. delivering sufficient daytime light levels to set the body clock, especially in the winter
  2. Vulnerable to disruption in power or data transmission- failure at any point in the circuit takes the whole system down
  3. Cost – to buy, install and commission additional hardware such as PoE switches and injectors
  4. Future proofing – these standards are changing fast and todays protocols risk becoming as obsolete as the floppy disc or VHS tape.


So what does that mean for you and me?

As professionals who design, deliver or manage spaces, PoE shifts the goal posts in ways we cannot begin to understand. Can a building ever be ‘intelligent’? Let alone ‘smart’ or intuitive?

Where does lighting end and controls begin? Who owns that data and how can we maintain our right to choose in the face of prescribed comfort and convenience?

What skills do we need to ensure that optimised digital-centric matrix serves rather than leads the process of creating the rich and dynamic analogue experience we all deserve.


Get in touch!