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Seeing Ultraviolet
Ian Ashdown, P. Eng., FIES, Senior Scientist, SunTracker Technologies Ltd. Published: 2015/10/26 UPDATE 15/11/08 - The following text briefly notes that some people can see near-ultraviolet radiation following cataract surgery due to the UV transmittance of...
Rethinking the Photometric Data File Format
Ian Ashdown, P. Eng., FIES, Senior Scientist, SunTracker Technologies Ltd. Published: 2017/03/01 If you perform lighting design calculations today, you can thank the efforts of the IES Computer Committee (IESCC) some thirty years ago. Its members recognized...
Phytochrome and PSS
Ian Ashdown, P. Eng., FIES, Senior Scientist, SunTracker Technologies Ltd. Published: 2016/12/09 Horticultural lighting is currently one of the fastest-expanding markets in commercial lighting, with projected revenues of several billion dollars in less than...
Photometry and Photosynthesis
Ian Ashdown, P. Eng., FIES, Senior Scientist, SunTracker Technologies Ltd. Published: 2014/12/10 UPDATE 15/04/13 -- This article was first published on December 10, 2014. A revised version was published as "LED Lighting for Horticulture" in the Mar/Apr 2015...
Mobile Light Pollution
Ian Ashdown, P. Eng., FIES, Senior Scientist, SunTracker Technologies Ltd. Published: 2016/01/21 At first glance, this appears to be an innocuous question: How much light pollution is attributable to automotive headlights? It is also a good question in that...
Mesopic Photometry and Statistics
Ian Ashdown, P. Eng., FIES, Senior Scientist, SunTracker Technologies Ltd. Published: 2014/04/21 One of the joys of statistics is that you can never be proven wrong ... In a previous All Things Lighting article titled "Understanding Mesopic Photometry"...
Light Pollution and Uplight Ratings
Ian Ashdown, P. Eng., FIES, Senior Scientist, SunTracker Technologies Ltd. Published: 2015/07/20 "Oh, East is East, and West is West, and never the twain shall meet." When Rudyard Kipling wrote this line in his poem The Ballad of East and West (Kipling...
Cerise365 and DAYSIM
Ian Ashdowna, Chris Jacksonb, Joel Spahnc, Todd Saemischd a. SunTracker Technologies Ltd., Victoria, Canada. b. Lighting Analysts Ltd., London, UK. c, d. Lighting Analysts Inc., Littleton, CO. Published: 2017/02/11 (Updated 2021/04/12) Ceriss365 and DAYSIM are...
Kruithof Revisited
Ian Ashdown, P. Eng., FIES, Senior Scientist, SunTracker Technologies Ltd. Published: 2015/11/24 A previous blog article -- The Kruithof Curve -- examined the history of the Kruithof curve (Kruithof 1941]) shown in FIG. 1: FIG. 1 – Kruithof curve, modern version...