FOCUS 057
Left Barings, London, by tp bennett, lighting by Hoare Lea: a layering approach allows lighting treatments to work independently or in combination to create different moods
Right Fisher Marantz Stone scheme for law firm Covington, San Francisco: the high level of daylight is balanced with an integrated scheme that considers every plane in the space
However, it has been pointed out that this measure fails to account for the role of rods (responsible for vision at low light levels) and cones (active at higher light levels and capable of colour vision), part of the visual system, despite studies which have shown their contribution to non-visual effects of light.
Meanwhile, a group of international researchers and specialists from the spheres of lighting, neurophysiological photometry, and sleep and circadian research has addressed light exposure, devising a series of recommendations of appropriate levels for daytime, evening and night. ‘Tere is an urgent need for evidence- led recommendations to help inform the design and application of light emission technologies and human exposures,’ they say. Teir recommendations are based on a new toolbox released last year by the International Commission on Illumination (CIE), which takes into account visual and non-visual photoreceptors. ‘Tere now exists an easily measured and internationally accepted SI-compliant system of metrology to inform lighting design and associated policy,’ said the group of researchers, which they believe provides a solid basis for their recommendations.
of measuring visual light, we also have to consider non- visual light and its impact on the human circadian system. For example, the WELL Standard has sought to consider the non-visual response in its stipulation of a metric called equivalent melanopic lux (EML) – to be precise, it calls for 200 EML vertically at the eye for four hours a day.
To the lighting layperson, and even a fair number of practitioners, these metrics can be abstruse and the mathematical equations impenetrable. Knitting all the issues together is a bit like string theory – somewhere there must be a unifying way of measuring lighting that is suitable for both the visual and non-visual systems. We may even already have arrived at it, but there is an element of finger in the wind about lighting metrics, to say nothing of much discussion and disagreement. Tis article is merely a stone skipping over some deep waters, indicating the complex issues that lie beneath the apparently simple proposition of specifying lighting for a space. It is also an indication of the massive rethink that lighting is undergoing in a number of directions. It will be interesting to see what the latest European standard on workplace lighting (EN 12464-1), expected this autumn, will make of it. Ultimately what is essential, and where there is consensus, is that the complete, three-dimensional visual environment and its occupants have to be considered if a lighting design is to be successful. Regardless of what metrics are arrived at, we now know two key things: human beings need to be in spaces which are visually stimulating, glare-free, comfortable and conducive, and that the lighting in those spaces must be sensitive to human biology and the circadian system with as high an element of daylight as possible.
Or as the highly respected, recently retired lighting consultant and teacher Barrie Wilde put it in a CIBSE Journal response to the manifesto: ‘Numbers and formulae predict, they do not create.’
LEFT: HUFTON + CROW RIGHT: JASON O’REAR
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