Academic Articles and Research Archives - All Things Lighting® Association

Evaluating Near-Horizontal Light Emission from Outdoor Lighting

Shirley Lang — Thu, 04 Jun 2026 21:18:23 +0000

Evaluating Near-Horizontal Light Emission from Outdoor Lighting DarkSky International – Tucson, AZ March 16, 2026 Executive Summary Upward-emitted outdoor light has long been identified as a source of atmospheric light pollution, a.k.a. sky glow. This form of light pollution is an obvious contributor to the brightening of the nighttime sky and can be observed as […]

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Technical Report: Photobiological Hazard Assessment of Orbital Solar Reflectors

Eric Bretschneider, Ph.D — Fri, 01 May 2026 20:08:58 +0000

Executive Summary This report details a photobiological hazard assessment of the general concept of Orbital Solar Reflectors (OSRs). A recent proposal, Reflect Orbital’s proposed Earendil-1 satellite is used as an exemplar. The analysis was conducted following IEC 62471:2006 Photobiological Safety of Lamps and Lamp Systems. OSRs are intended to provide primary or supplemental lighting and […]

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Intro to Horticultural Lighting

Alexander Willemsen — Wed, 04 Feb 2026 17:40:12 +0000

Introduction This article is based on a presentation I had the pleasure of delivering at the recent Canada Light Expo 2025 in Toronto. My aim with the presentation was to offer a brief overview of some key aspects of horticultural lighting and to highlight how it differs from architectural lighting. I was surprised by the […]

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Refinements to the Worthing Relationship – A Quantum Version of Wien’s Displacement Law

Eric Bretschneider, Ph.D — Wed, 05 Nov 2025 00:00:55 +0000

Refinements to the Worthing Relationship – A Quantum Version of Wien’s Displacement Law Eric Bretschneider, Ph.D. Abstract Wien’s Displacement Law is a simple equation that allows calculation of the peak wavelength for a black body light source as a function of temperature. However, not all uses of light are based on radiant flux. In particular, […]

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Finding the Danger Zone of the Circadian Stimulus Model: A Summary

Alexander Willemsen — Tue, 04 Nov 2025 23:55:01 +0000

Author: Alexander Willemsen, Degree of Master of Science of Engineering Based on a paper authored by Eric Bretschneider, Ph.D. The Circadian Stimulus (CS) model is one of the most well-known models for quantifying the circadian impact of lighting. One striking feature that separates the model from other contemporary circadian lighting models is its discontinuous action […]

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Can Designs and Measurements Based on the Circadian Stimulus Model Stand the Test of Time?

Eric Bretschneider, Ph.D — Tue, 13 Aug 2024 06:01:18 +0000

Author: Eric Bretschneider, Ph.D INTRODUCTION When considering the potential circadian impact of lighting, lighting designers have a choice between three different models: melanopic equivalent daylight illuminance, or m-EDI [CIE 2018]; equivalent melanopic lux, or EML [WELL v2]; and circadian light, or CLA [UL 2019]. Both m-EDI and EML have a continuous action spectrum, which means […]

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Lighting Uniformity in Horticulture

Shirley Lang — Fri, 24 Jun 2022 03:34:28 +0000

Written in 2015, “Greenhouse Design and Control” (Ponce et al. 2015) is extraordinarily comprehensive in its coverage of greenhouse design issues, from site selection through structural load bearing analysis and ventilation technologies to greenhouse automation using adaptive neural fuzzy inference systems. On the topic of greenhouse lighting, however, it has only this to say: “The light level in the greenhouse should be adequate and uniform for crop growth.”

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Modeling Spherical Irradiance for UV-C Air Disinfection

Shirley Lang — Fri, 20 May 2022 13:29:02 +0000

We have been using ultraviolet radiation as a means of disinfection for over a century. However, it has been the unfortunate events of the past year that have led to an explosion of interest in ultraviolet germicidal irradiation (UVGI) systems. From mercury vapour and pulsed xenon lamps to excimer lamps and ultraviolet LEDs, there have […]

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Visible Light Disinfection

Shirley Lang — Thu, 19 May 2022 19:45:38 +0000

In summary, visible light disinfection technology may be useful in some applications, but it is by no means a panacea. When designing or specifying a disinfection system, both the lighting designer and the client will need to thoroughly understand the capabilities and limitations of the technology, and agree upon its purpose.

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Quantifying Light Pollution Sources

Shirley Lang — Thu, 03 Feb 2022 08:02:02 +0000

time light pollution is sadly familiar to all of us. While our grandparents and great-grandparents may talk fondly of seeing the Milky Way in their youth, with thousands of stars scattered across the dark summer sky, we are mostly content with seeing a few dozen stars through the never-ending dusk of urban and suburban skies.

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Defining Far-Ultraviolet

Shirley Lang — Fri, 12 Nov 2021 00:00:49 +0000

In these uncertain times, there is increasingly persuasive evidence that “far-UV” radiation is effective in inactivating the SARS-CoV-2 virus and other pathogens, but without the health risks of germicidal ultraviolet radiation. Unfortunately, this technology has some of the hallmarks of a “miracle cure,” which has become an irresistible attractant for charlatans and hucksters of all […]

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Visual Glare and CIE 117-1995 – NEMA White Paper

Shirley Lang — Wed, 13 Oct 2021 00:18:13 +0000

The CIE Unified Glare Rating (UGR) metric has been use by the architectural lighting industry since it was first published by the CIE a quarter-century ago (CIE 117-1995, Discomfort Glare in Interior Lighting). Originally popularized by European lighting manufacturers, UGR has recently been adopted by the DesignLights Consortium, the US Green Building Council (LEED), and […]

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Horticultural Lighting Design and Déjà Vu

Shirley Lang — Mon, 13 Sep 2021 00:25:34 +0000

The phrase déjà vu translates from French as “already seen,” which nicely describes a current issue with horticultural lighting design. The introduction of LED technology may have kick-started horticultural lighting as an innovative industry, but we have yet to learn an important lesson from four decades of architectural lighting. The Importance of Design Data Prior to the […]

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The Effect of Near-Infrared Radiation on Plants

Shirley Lang — Mon, 19 Apr 2021 09:00:25 +0000

Look at any textbook on botany and you will find this maxim: plants respond to optical radiation in the spectral range of 280 nm to 800 nm. Period, end of discussion. The question is, how was this spectral range (sometimes referred to as Photobiologically Active Radiation, or PBAR) determined? This question addresses issues beyond mere […]

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Specifying LED Colors for Horticultural Lighting

Shirley Lang — Fri, 29 Jan 2021 08:09:02 +0000

This paper proposes an LED “color” specification that represents a given SPD using a small number of radial basis functions, to provide a metric for comparing biologically similar SPDs. It further introduces a trainable fuzzy logic SPD classifier that can compare biologically similar SPDs for specific horticultural applications.

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Ultraviolet Radiation & Viral Misinformation

Shirley Lang — Mon, 04 Jan 2021 04:19:44 +0000

Let me begin with a smorgasbord of headlines: 99.9% of Covid-19 virus dead in 30 seconds with UV LEDs, says Tel Aviv research (www.malaysianow.com) UV-emitting LED lights found to kill coronavirus (www.sciencedaily.com) Study reveals UV LED lights effectively kill a human coronavirus (www.medicalnewstoday.com) You can kill Covid with a flick of a switch, study shows […]

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Ultraviolet Radiation Terminology

Shirley Lang — Mon, 14 Sep 2020 05:03:03 +0000

A word of caution: I am going to be annoyingly pedantic here, but with good reason. The lighting industry has a century-long history of introducing unfamiliar technologies using familiar terminology. We later come to regret our choice of words when it becomes necessary to express precisely what we mean. Consider, for example, the term luminance. […]

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Spherical Irradiance and Aerosols

Shirley Lang — Thu, 20 Aug 2020 05:12:29 +0000

Lighting designers will be familiar with the illuminance of a planar surface, which is measured in lumens per square meter (or foot). The irradiance of a planar surface by a germicidal radiation source is conceptually the same, except that it is measured in watts per square meter (W/m2). Most designers, however, will not be familiar […]

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Defining Photosynthetic Photon Efficacy

Shirley Lang — Fri, 26 Jun 2020 19:39:58 +0000

There has been some discussion online and in presentations recently about the issue of photosynthetic photon flux. The argument goes as follows: Photosynthetically Active Radiation (PAR) is somewhat arbitrarily defined as optical radiation within the spectral range of 400 nm to 700 nm. Exposing plants to far-red radiation (defined as 700 nm to 800 nm) […]

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Designing an Ultraviolet-C Disinfection System

Shirley Lang — Tue, 09 Jun 2020 22:59:59 +0000

Recent germicidal light sources include UV-C light-emitting diodes and pulsed xenon discharge lamps, but there is a newcomer on the block that has gained considerable media attention: far-ultraviolet excimer lamps. What does it take to design a UV-C disinfection system using far-UV radiation?

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