Alliance for Lighting Information

Table of Contents

Technical terms
About ALI

What's New

Circadian Stimulus and S/P Ratios
discusses the directly proportional relationship between a light source's S/P ratio - used widely now in marketing - and its corresponding stimulus to the human circadian system.


is a complex and important issue in outdoor lighting, and some topics are discussed here along with links to more information.
are involved in outdoor lighting design and maintenance decisions. This page introduces the issues and provides links to more information within the ALI website.
Environmental Effects
from outdoor lighting are evident and hidden. This page presents some of the signfiicant issues and links to more information in the ALI website.
Legislation and Ordinances
are being proposed and adopted in many areas, from local jurisdictions up to states (so far). This page cites some of the issues and provides links to information with the ALI website that may be relevant to lighting legislation and ordinances.
Light Pollution or Skyglow
is a growing concern and to some extent depends on choices made when lighting systems are designed. This page introduces the issues and provides links to more information within the ALI website.
Older Eyes
work differently under outdoor lighting levels and conditions, particularly driving at night. This page provides brief information about the most important effects of aging on vision, and includes links to more information within the ALI website.
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Technical terms

Efficacy of Metal Halide and High Pressure Sodium Sources
End-of-Life Lamp Lumen Data
Initial and Maintained Conditions
Lamp Lumen Depreciation (LLD)
Light Loss Factor (LLF)
"Mean" for Metal Halide and High Pressure Sodium Sources
Rated Life of Metal Halide and High Pressure Sodium Sources
Rated Lumens and Initial Efficacy
Rayleigh Scatter Index (RSI)
Uniformity Ratio
Unit Power Density (UPD)
Unit Uplight Density (UUD)
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Recurring Errors in Ordinances: Site Uniformity and Property Line Limitations
discusses the problems that misunderstood and misapplied elements in ordinances can produce - even repeatedly in some documents like the current proposals in Boulder, Castle Rock and Arapahoe County.
Roadway Lighting Research
discusses the findings from research into Unit Power Density (UPD) and Unit Uplight Density (UUD), published in four papers by David Keith in the Journal of the IESNA from 2000 through 2003.
There is More to Lighting Quality Than What Meets the Eye
presents the issues involved in outdoor lighting quality, recognizing that the visual appearance and performance of a lighting system are only part of the complete story.
Uniformity Ratios in Ordinances
discusses the way such ratios are defined and implemented in lighting ordiances, along with problems that occur when the implications of uniformity ratios are not undestood.
What Blue Skies Tell Us About Light Pollution
is a introduction to the issues of skyglow and particularly evaluation of relative contributions by different light sources.
Why MH Systems Cost More Than HPS Systems
discusses the relative costs - in monetary and environmental terms - of choosing Metal Halide or High Pressure Sodium sources for outdoor lighting.
Xenon Headlights
are a nuisance (or worse!) for many drivers and this discussion includes review of the relevant standards and reasons why these headlights are such a pain in the eye.
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Sources and Surfaces - Evaluating Spectral Distribution Interactions Using Roadway Signage
by Jefferey F. Knox & David M. Keith, discusses the revision of lighting calculations to evaluate color difference instead of luminous contrast, and reports on the results of applying these methods to roadway signage using fifteen different light soures described by induvidual spectral power distributions.
Learning from Roadway Lighting Research
is the Powerpoint presentation (1,115 kB) made in October 2002 for a leading manufacturer's luminaire design staff.
Legislation, Ordinances and Energy Codes: the Future for Outdoor Lighting
- an outline of the the presentation made to the IEEE 2003 Regional Conference in Denver, CO in March. The Powerpoint presentation (255 kB) is available here.
IESNA Street and Area Lighting Committee 2001
conference included this Powerpoint presentation about research into Unit Power Density (UPD), with special emphasis on the potential reduction of uplight.
Sources, Surfaces and Scatter
is the Powerpoint presentation made to the International Dark-sky Association 2003 Annual Conference in Tuscon, AZ in March The abstract is available here.
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Roadway Unit Uplight Density (UUD) Calculation Examples
includes information about calculating UUD with references and examples.
Sources, Surfaces and Atmospheric Scatter: The Rayleigh Scatter Index
is the paper submitted to the International Dark-sky Association 2003 Annual Conference in Tuscon, AZ in March. The abstract is here.
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