Reader Opinion | Mar 19, 2016

Discussion: The Value of Dark Skies - About Environmentally Friendly Lighting

For many years no one worried about light pollution: on the contrary, the brighter the better. Then it became evident that darkness also has its value. J. Scott Feierabend, executive director of the International Dark-Sky Association (IDA), presents and explains in detail, the latest ndings and suggestions published in the “New IDA LED Lighting Practical Guide” and “New IDA Standards on Blue Light at Night”. He also discusses how to illuminate public areas while avoiding excess light pollution.

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LpR#54 Article, page 80

The Value of Dark Skies - About Environmentally Friendly Lighting by J. Scott Feierabend, International Dark-Sky Association (IDA)

Peter Schwarcz says: (on Mar 22, 2016 10:56 PM)
Figure 4 shows a comparison of the spectrum of white LEDs (solid lines) with the response of the human visual system in the photopic regime (dashed lines). The photopic spectral sensitivity function V(λ) was defined in 1924 and applicable to human eyes fully adapted to high lighting level, usually quantified as 5 cd/m2 or above. The streetlighting levels are usually lower than that, they are between 0,3 and 2 cd/m2. Under this lighting adaptation level, the spectral sensitivity function is described with mesopic photometry. Mesopic vision is a combination of photopic vision and scotopic vision in low but not quite dark lighting situations. Most night-time outdoor and traffic lighting scenarios are in the mesopic range. More details can be found in CIE Technical report 191:2010: Recommended System for Mesopic Photometry based on Visual Performance.

I have been working with astronomers on lighting topics for two decades. I was there, when the first Hungarian dark sky park project was initiated in 2006. I am enjoying the common efforts for providing proper light with the full respect of environmental considerations and scientific evidence of light and vision.

Péter Schwarcz
Director of Division5 of CIE
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