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Color Rendering & Color Gamut Metrics Terry Mcgowan Change Is Finally Underway … Dir

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Color Rendering & Color Gamut Metrics Terry Mcgowan Change Is Finally Underway … Dir The IESTM-30 – New Color Rendering & Color Gamut Metrics Terry McGowan Change Is Finally Underway … Dir. of Engineering American Lighting Association 1 . Why Do Lighting Regulations Include Color Requirements? Topics . The Strange Metrics Involved . Changes Have Long Been Needed 2 Color Is Part of Lighting . Light Source Performance ( Especially Regulations – LPW) Especially Lighting . User Acceptance of New Lamp Products Efficiency . Lighting Applications (Quality of Light) Regulations- . Price Because Light Source Color Impacts: 3 . DOE Which . Energy Star Lamps and Luminaires Regulations? . California (CEC) Title 20 & Title 24 Via the JA-8 Appendix 4 . Chromaticity (Correlated Color Temperature or CCT) What Color . Color Rendering Characteristics . Color Shift Over Life Are . Color Angular Uniformity (Directional Regulated? Light Sources) 5 Spectral Power Distributions How Should These Spectral Characteristics Be Described? 6 Chromaticity The CIE System of Colorimetry Based Upon The Trichromatic Nature of Human Vision CIE Color Space (1931 with revisions in 1960, 1964 1976 and 1991) 7 Chromaticity Of Common Light Sources 8 Chromaticity & Representations of Color Space Hue Saturation Brightness 9 The Color Characteristics Of Light Sources Which Is The Most Important? What’s The Analysis Process? 10 Chromaticity Energy Star Lamp Specification (V1.1) Effective 9/30/14 11 Chromaticity Specification Tolerance Limits (1976 CIE u’ v’ Diagram) * *jnd = Just Noticeable Difference 12 Chromaticity Energy Star Lamp Specification (V1.1) - Change Over Time 13 Chromaticity Energy Star Lamp Specification (V1.1) - Beam Angle Variation Limits 14 Color Rendering “Another Fine Mess ….”* *Movie title - Laurel and Hardy 1930 15 CHROMATICITY COLOR RENDERING Think of it this The overall color The appearance of way … impression or tone colors when you look (tint) that you see at people and things when you look at the light source 16 Light & Color & Seeing Measureable & Not So Measureable 17 Color Rendering Index (Ra) “Color Fidelity” A calculated value that compares the rendering of a set of 8 or 14 color samples under a test (ideal) light source compared to a reference light source of the same chromaticity Based upon CIE W*U*V* uniform color space(1964) 18 CRI Issues – Energy Star Requirements Energy Star Lamps V1.1, Effective September 1, 2014 19 Based upon a limited set of color samples Unreliable for LED light sources Color Limited applicability Rendering Now, not recommended for use “in energy Index regulations to characterize color attributes Issues: for solid state lighting ….” - IES (August, 2014) 20 Other Ways To Express Color Rendering Information: 21 Compliment To CRI: Gamut Area Index (GAI) “GAI can help ensure both good color discrimination and satisfactory perceptions of object color “vividness” and “naturalness”. (Rea and Freyssinier-Nova, Lighting Research Center “Color Rendering: A Tale of Two Metrics” CR&A, 9/07.) 22 CRI Alternative & Improvement: Color Quality Scale (CQS) 23 New (TM-30) “Color Fidelity” Metric = Rf Average Color Gamut Area = Rg Color Distortion/Color Saturation Icon 24 Comparing The Old Ra With The New Rf Source: DOE LightFair 5/15 25 Comparing The Old Ra With The New Rf 26 . Current regulations generally include requirements for light source chromaticity and color rendering (CRI = Ra) . Such requirements do not ensure quality lighting . CRI/Ra is a flawed metric for LEDs and other SS light Summary: sources . Improved metrics exist, but have not yet been agreed upon and adopted via the standards process . From a lighting design standpoint, both chromaticity and color rendering metrics are starting points – indicators of what to expect; but they are not a substitute for the actual visual experience 27.
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