Featured
Quantifying Light Pollution Sources
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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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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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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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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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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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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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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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 […]Read More April 19, 2021
Near-infrared radiation, Photobiologically Active Radiation, phytochrome, R:FR ratio -
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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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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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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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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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) […]
-
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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Recent advances in LED-based luminaire design have enabled greenhouse operators to temporally control both the photon flux density and spectral irradiance incident upon the plant canopy.
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Supplemental electric lighting for greenhouses may be essential for extending the growing season in northern climates, but it comes with a not-so-hidden cost: environmental light pollution. The consequences of this pollution may range from irate neighbours in rural areas to municipal bylaws that may prohibit the use of supplemental lighting during certain hours of the […]
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In these unfortunate times, it seems that everyone is looking for ways to help with the COVID-19 crisis. From a lighting designer’s perspective, one solution is obvious: ultraviolet radiation. We have known about the disinfectant properties of ultraviolet radiation for nearly 150 years (Downes and Blunt 1877), and we have been using low-pressure mercury arc […]
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Ian Ashdown, P. Eng, FIES, Senior Scientist, SunTracker Technologies Ltd. Published: 19/11/14. Whether you call it “circadian lighting,” “biologically effective lighting” or some other name, the principle is the same: the color and intensity of light can be used to regulate the timing of our biological clocks, or “circadian rhythms.” For architects and lighting designers, […]Read More November 15, 2019
circadian lighting, circadian stimulus, UL RP 24480, WELL building standard -
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Ian Ashdown, P. Eng., FIES, Senior Scientist, SunTracker Technologies Ltd. Published 18/06/04. Most LED grow lights feature blue and red LEDs whose peak wavelengths – approximately 450 nm for blue and 660 nm for red – have been chosen to coincide with the spectral absorption peaks of chlorophyll A and B molecules. In doing so, […]Read More November 14, 2019
end of day, far-red lighting, long-day plants, night breaks, phytochrome, R:FR ratio, short-day plants
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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.Read More February 3, 2022
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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.”Read More June 23, 2022
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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.
-
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 […]
-
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.
-
The IES has introduced ANSI/IES RP-45-21, Recommended Practice: Horticultural Lighting, to describe the differences between architectural and horticultural lighting design. The document is paramount for lighting professionals interested in designing atria, greenhouses and indoor farms.
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What does the metaverse, the promised “next chapter for the internet” (Mark Zuckerberg, 2021), have to do with architectural lighting? It will be after all an immersive virtual world where people will gather to socialize, play, and work.
-
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 […]
-
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 […]
-
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 […]
-
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 […]Read More April 19, 2021
Near-infrared radiation, Photobiologically Active Radiation, phytochrome, R:FR ratio -
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.
-
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 […]
-
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. […]
-
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 […]
-
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) […]
-
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?
-
Recent advances in LED-based luminaire design have enabled greenhouse operators to temporally control both the photon flux density and spectral irradiance incident upon the plant canopy.
-
Supplemental electric lighting for greenhouses may be essential for extending the growing season in northern climates, but it comes with a not-so-hidden cost: environmental light pollution. The consequences of this pollution may range from irate neighbours in rural areas to municipal bylaws that may prohibit the use of supplemental lighting during certain hours of the […]
-
In these unfortunate times, it seems that everyone is looking for ways to help with the COVID-19 crisis. From a lighting designer’s perspective, one solution is obvious: ultraviolet radiation. We have known about the disinfectant properties of ultraviolet radiation for nearly 150 years (Downes and Blunt 1877), and we have been using low-pressure mercury arc […]
-
Ian Ashdown, P. Eng, FIES, Senior Scientist, SunTracker Technologies Ltd. Published: 19/11/14. Whether you call it “circadian lighting,” “biologically effective lighting” or some other name, the principle is the same: the color and intensity of light can be used to regulate the timing of our biological clocks, or “circadian rhythms.” For architects and lighting designers, […]Read More November 15, 2019
circadian lighting, circadian stimulus, UL RP 24480, WELL building standard