Lighting Matters: Scotopic Richness…What the Experts Say – Monthly Column featured in EE Publisher’s Vector Magazine

In Vector’s last issue, I started our discussion on the scotopic richness of artificial light sources. In this month’s column, we focus on the opinions of experts and international bodies on this subject. But first, a glimpse at the history, which will astound many.

In the early 1990s, Dr Samuel Berman and fellow professor emeritus and scientist Dr Don Jewitt, a neurophysiologist at the University of California Medical Centre, discovered that more light is not necessarily better than less light for the function of the human visual system. Their study found “a correlation between the rod photoreceptors and the degree to which the eye opens and closes to regulate the amount of light entering the eye. Lighting is better for the human visual system when it is scotopically enhanced – meaning less light energy and more wavelengths in the blue-green range.” That means that the rods are stimulated by the shorter wavelengths, taking us back to the fact that, when we use scotopically rich light sources, the rods will work with the cones, thereby enhancing our visual efficiency, meaning that we require less light.

It has taken from around 1995 – the 2011 International Commission on Illumination (CIE) Congress at Sun City; the acknowledgement by the Illuminating Engineering Society of North America (IESNA) and, more recently, the CIE mid-term meeting on the Island of Jeju, Korea, in October 2017 – to acknowledge that the science and copious research is valid.

Renowned British architect Sir Nicholas Grimshaw noted that we over-illuminate by some 50% and that architects should learn more about lighting. Once again, I was reminded of the International Ophthalmic Conference, which found that over-illumination levels were generally in the order two to five times more than is required for human visual efficiency.

You may be wondering how to overcome this situation. Well, the answer is simple: It is vital to acquire the knowledge, understanding and know-how to practically implement lighting design which will take the scotopic richness of light sources into account.

In our next issue, I will discuss how the scotopic richness of light sources ties in with Human Centric Lighting, and all the other new elements of the lighting revolution which form part of the fourth industrial revolution.



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