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About the IES
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IES Staff
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Information
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Annual Report
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Membership
Join
Committees & Panels
Sustaining Membership
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University Program
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Section Directory
Section Resources
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Philanthropic Donations
Events
Information
Events Calendar
Sponsorship
IES Progress Report
Featured Events
Light + Justice Symposium
IES24 Conference
Street & Area Lighting Conference
Research Symposium
Special Events
Light for Life®: Museum Symposium
Illumination Awards & Gala
Lighting Education Tour
Aviation Lighting Conference
Research & Education
Research
About IES Research
Publications
FIRES Forum
Past Projects
IES Lighting Ready Reference App
Education
eLearning Portal
Upcoming Webinars
Request IES CEU/AIA-LUs
LC Study Group
Register Now for Our Next Webinar
Standards
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Purchase Standards
Browse Standards
Nomenclature & Definitions
Standards Errata & Addenda
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Standards in Public Review
Toolbox
IES Standards Toolbox
My Lighting Library
My Illuminance Selector
My Reference Retriever
LD+A
Store
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Weber’s fraction
[5.9.4.3] (See
luminance contrast
.)
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