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Design lighting “for the body, not just the eyes”

LONDON– Lighting designers must learn to design for the biological as well as the visual effects of light, PhotonStar’s Fenella Frost told LuxLive yesterday.

In a presentation on the latest research into ‘human-centric lighting’, Frost said that light is the most powerful time-cue for setting our body clocks, and that a lack of light at the right time – or being exposed to the wrong light at the wrong time – can cause ‘a huge number of disorders’.

‘Our visual needs and our biological needs are very different,’ she said. ‘And lighting design really does need to change to take into account both these effects of light.’

Lighting’s impact on the body is already being taken into consideration in lighting for healthcare, education and zoological applications.

But Frost said: ‘Lighting designers need to have clearer guidelines on what to do, and there’s a lot of misinformation.’

Different metrics can be used to distinguish between the different effects of light, she said. Photopic lux may be the relevant metric for evaluating a visual effect, but we must also consider ‘melanopic lux’, which looks at light’s impact on the release of melatonin, which is linked to the amount of blue light in the spectrum.

Although the spectrum of daylight provides a good range of colours, and so delivers high levels of photopic and melanopic lux, artificial sources that appear visually as bright may not have the same biological effect because their spectrums are strong in some colours and weak in others.

We must understand how different levels of light affect us, Frost said. ‘Current research is showing that you can phase shift somebody with 100lx normal white light, moving [the body clock] by up to two hours a day. With normal lighting, we can entrain somebody’s circadian rhythm.’

Frost said her own knowledge of this had allowed her to overcome jet lag on long-haul flights. ‘I travel with an understanding of this, and I have a plan involving sunglasses on planes,’ she said.

On a hospital ward, where lights must be left off at night for the benefit of patients, nurses could come to a brighter area for 10 minutes every hour to get enough light to keep them sufficiently alert.

PhotonStar’s new ChromaWhite 2.0 system uses automatic circadian tuning, changing the spectral composition of light at different times of day to fit in with the body clock and promote healthy activity, rest and sleep.

Frost said the change in approach could mean that lighting design becomes ‘more essential’. ‘A lot of people use excuses not to use lighting designers – I’d like to see lighting designers used more.’