A Correlated Color Temperature for Illuminants
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Light and Color
Chapter 9 LIGHT AND COLOR What Is Color? Color is a human phenomenon. To the physicist, the only difference be- tween light with a wavelength of 400 nanometers and that of 700 nm is Different wavelengths wavelength and amount of energy. However a normal human eye will see cause the eye to see another very significant difference: The shorter wavelength light will different colors. cause the eye to see blue-violet and the longer, deep red. Thus color is the response of the normal eye to certain wavelengths of light. It is nec- essary to include the qualifier “normal” because some eyes have abnor- malities which makes it impossible for them to distinguish between certain colors, red and green, for example. Note that “color” is something that happens in the human seeing ap- Only light itself paratus—when the eye perceives certain wavelengths of light. There is causes sensations of no mention of paint, pigment, ink, colored cloth or anything except light color. itself. Clear understanding of this point is vital to the forthcoming discus- sion. Colorants by themselves cannot produce sensations of color. If the proper light waves are not present, colorants are helpless to produce a sensation of color. Thus color resides in the eye, actually in the retina- optic-nerve-brain combination which teams up to provide our color sen- Color vision is sations. How this system works has been a matter of study for many years complex and not and recent investigations, many of them based on the availability of new completely brain scanning machines, have made important discoveries. -
Calculation of CCT and Duv and Practical Conversion Formulae
CORM 2011 Conference, Gaithersburg, MD, May 3-5, 2011 Calculation of CCT and Duv and Practical Conversion Formulae Yoshi Ohno Group Leader, NIST Fellow Optical Technology Division National Institute of Standards and Technology Gaithersburg, Maryland USA CORM 2011 1 White Light Chromaticity Duv CCT CORM 2011 2 Duv often missing Lighting Facts Label CCT and CRI do not tell the whole story of color quality CORM 2011 3 CCT and CRI do not tell the whole story Triphosphor FL simulation Not acceptable Not preferred Neodymium (Duv=-0.005) Duv is another important dimension of chromaticity. CORM 2011 4 Duv defined in ANSI standard Closest distance from the Planckian locus on the (u', 2/3 v') diagram, with + sign for above and - sign for below the Planckian locus. (ANSI C78.377-2008) Symbol: Duv CCT and Duv can specify + Duv the chromaticity of light sources just like (x, y). - Duv The two numbers (CCT, Duv) provides color information intuitively. (x, y) does not. Duv needs to be defined by CIE. CORM 2011 5 ANSI C78.377-2008 Specifications for the chromaticity of SSL products CORM 2011 6 CCT- Duv chart 5000 K 3000 K 4000 K 6500 K 2700 K 3500 K 4500 K 5700 K ANSI 7-step MacAdam C78.377 ellipses quadrangles (CCT in log scale) CORM 2011 7 Correlated Color Temperature (CCT) Temperature [K] of a Planckian radiator whose chromaticity is closest to that of a given stimulus on the CIE (u’,2/3 v’) coordinate. (CIE 15:2004) CCT is based on the CIE 1960 (u, v) diagram, which is now obsolete. -
Goethe's Theory of Colors Between the Ancient Philosophy, Middle Ages
CULTURE, MEDIA & FILM | RESEARCH ARTICLE Goethe’s theory of colors between the ancient philosophy, middle ages occultism and modern science Victor Barsan and Andrei Merticariu Cogent Arts & Humanities (2016), 3: 1145569 Page 1 of 29 Barsan & Merticariu, Cogent Arts & Humanities (2016), 3: 1145569 http://dx.doi.org/10.1080/23311983.2016.1145569 CULTURE, MEDIA & FILM | RESEARCH ARTICLE Goethe’s theory of colors between the ancient philosophy, middle ages occultism and modern science 1 2 Received: 18 February 2015 Victor Barsan * and Andrei Merticariu Accepted: 20 January 2016 Published: 18 February 2016 Abstract: Goethe’s rejection of Newton’s theory of colors is an interesting example *Corresponding author: Victor Barsan, of the vulnerability of the human mind—however brilliant it might be—to fanati- Department of Theoretical Physics, cism. After an analysis of Goethe’s persistent fascination with magic and occultism, Horia Hulubei Institute of Physics and Nuclear Engineering, Aleea Reactorului of his education, existential experiences, influences, and idiosyncrasies, the authors nr. 30, Magurele, Bucharest, Romania E-mail: [email protected] propose an original interpretation of his anti-Newtonian position. The relevance of Goethe’s Farbenlehre to physics and physiology, from the perspective of modern sci- Reviewing editor: Peter Stanley Fosl, Transylvania ence, is discussed in detail. University, USA Subjects: Aristotle; Biophysics; Experimental Physics; Fine Art; Medical Physics; Ophthal- Additional information is available at the end of the article mology; Philosophy of Art; Philosophy of Science; Presocratics Keywords: ancient philosophy; Greek–Roman classicism; middle ages science; Newtonian science; occultism; pantheism; optics; theory of colors; primordial phenomenon (urphaeno men) 1. Introduction Light is one of the most interesting components of the physical universe. -
Calculating Correlated Color Temperatures Across the Entire Gamut of Daylight and Skylight Chromaticities
Calculating correlated color temperatures across the entire gamut of daylight and skylight chromaticities Javier Herna´ ndez-Andre´ s, Raymond L. Lee, Jr., and Javier Romero Natural outdoor illumination daily undergoes large changes in its correlated color temperature ͑CCT͒, yet existing equations for calculating CCT from chromaticity coordinates span only part of this range. To improve both the gamut and accuracy of these CCT calculations, we use chromaticities calculated from our measurements of nearly 7000 daylight and skylight spectra to test an equation that accurately maps CIE 1931 chromaticities x and y into CCT. We extend the work of McCamy ͓Color Res. Appl. 12, 285–287 ͑1992͔͒ by using a chromaticity epicenter for CCT and the inverse slope of the line that connects it to x and y. With two epicenters for different CCT ranges, our simple equation is accurate across wide chromaticity and CCT ranges ͑3000–106 K͒ spanned by daylight and skylight. © 1999 Optical Society of America OCIS codes: 010.1290, 330.1710, 330.1730. 1. Introduction term correlated color temperature ͑CCT͒ instead of A colorimetric landmark often included in the Com- color temperature to describe its appearance. Sup- mission Internationale de l’Eclairage ͑CIE͒ 1931 pose that x1, y1 is the chromaticity of such an off-locus chromaticity diagram is the locus of chromaticity co- light source. By definition, the CCT of x1, y1 is the ordinates defined by blackbody radiators ͑see Fig. 1, temperature of the Planckian radiator whose chro- inset͒. One can calculate this Planckian ͑or black- maticity is nearest to x1, y1. The colorimetric body͒ locus by colorimetrically integrating the Planck minimum-distance calculations that determine CCT function at many different temperatures, with each must be done within the color space of the CIE 1960 temperature specifying a unique pair of 1931 x, y uniformity chromaticity scale ͑UCS͒ diagram. -
Cooledge Light Quality Metrics Fabricated
COOLEDGE LIGHT QUALITY METRICS: FABRICATED LUMINAIRES - 3500K NOTES ABOUT LIGHT QUALITY METRICS DATA: ― Values shown are TYPICAL – actual performance of individual units may vary ― The data presented has been generated in accordance with LM-79-08 ― A complete summary of LM-79-08 data is provided for nominal 4x8 (1200x2400) FABRICated Luminaire models only; however, spectral and color rendering data is applicable to all luminaire sizes, models, and flux levels including: ― Spectral Power Distribution (SPD) ― Nominal CCT ― Chromaticity ― Rf and Rg (TM-30-15) ― CRI (Ra) and R-values ― Duv SELECTED DEFINITIONS ― Candlepower: As presented in this document it is the same as “candela” the SI unit of measurement for light intensity. ― CRI (Ra): The general Color Rendering Index based on 8 CIE reference pastel color samples. ― Duv: The American National Standards Institute (ANSI) references Duv, a metric based on the CIE 1976 color space that quantifies the distance between the chromaticity of a given light source and a blackbody radiator of equal CCT. A negative Duv indicates that the source is “below” the Planckian locus (blackbody curve), potentially having a red/ blue tint, whereas a positive Duv indicates that the source is “above” the curve, potentially exhibiting a green tint. ― Nominal CCT Quadrangles: ANSI has defined acceptable chromaticity quadrangles for LED binning in relation to the blackbody curve within CIE color space. The data presented shows the typical chromaticity coordinate within the relevant quadrangle. ― R-value (Ri): The R-value is a mathematical calculation measuring how similar a light source renders a particular color compared to a reference blackbody source of the same CCT. -
Fuzzy Set Theoretical Approach to the Tone Triangular System
JOURNAL OF COMPUTERS, VOL. 6, NO. 11, NOVEMBER 2011 2345 Fuzzy Set Theoretical Approach to the Tone Triangular System Naotoshi Sugano Tamagawa University, Tokyo, Japan [email protected] Abstract—The present study considers a fuzzy color system gravity of the attribute information of vague colors. This in which three input fuzzy sets are constructed on the tone fuzzy set theoretical approach is useful for vague color triangle. This system can process a fuzzy input to a tone information processing, color identification, and similar triangular system and output to a color on the RGB applications. triangular system. Three input fuzzy sets (not black, white, and light) are applied to the tone triangle relationship. By treating three attributes of chromaticness, whiteness, and II. METHODS blackness on the tone triangle, a target color can be easily A. Color Triangle and Additive Color Mixture obtained as the center of gravity of the output fuzzy set. In Additive color mixing occurs when two or three beams the present paper, the differences between fuzzy inputs and inference outputs are described, and the relationship of differently colored light combine. It has been found between inference outputs for crisp inputs and for fuzzy that mixing just three additive primary colors, red, green, inputs on the RGB triangular system are shown by the and blue, can produce the majority of colors. In general, a input-output characteristics between chromaticness, color vector can be described by certain quantities as a whiteness, and blackness as the inputs and redness (as one scalar and a direction. These quantities are referred to as of the outputs). -
Calculating Color Temperature and Illuminance Using the TAOS TCS3414CS Digital Color Sensor Contributed by Joe Smith February 27, 2009 Rev C
TAOS Inc. is now ams AG The technical content of this TAOS document is still valid. Contact information: Headquarters: ams AG Tobelbader Strasse 30 8141 Premstaetten, Austria Tel: +43 (0) 3136 500 0 e-Mail: [email protected] Please visit our website at www.ams.com NUMBER 25 INTELLIGENT OPTO SENSOR DESIGNER’S NOTEBOOK Calculating Color Temperature and Illuminance using the TAOS TCS3414CS Digital Color Sensor contributed by Joe Smith February 27, 2009 Rev C ABSTRACT The Color Temperature and Illuminance of a broad band light source can be determined with the TAOS TCS3414CS red, green and blue digital color sensor with IR blocking filter built in to the package. This paper will examine Color Temperature and discuss how to calculate the Color Temperature and Illuminance of a given light source. Color Temperature information could be useful in feedback control and quality control systems. COLOR TEMPERATURE Color temperature has long been used as a metric to characterize broad band light sources. It is a means to characterize the spectral properties of a near-white light source. Color temperature, measured in degrees Kelvin (K), refers to the temperature to which one would have to heat a blackbody (or planckian) radiator to produce light of a particular color. A blackbody radiator is defined as a theoretical object that is a perfect radiator of visible light. As the blackbody radiator is heated it radiates energy first in the infrared spectrum and then in the visible spectrum as red, orange, white and finally bluish white light. Incandescent lights are good models of blackbody radiators, because most of the light emitted from them is due to the heating of their filaments. -
Raphics & Visualization
Graphics & Visualization Chapter 11 COLOR IN GRAPHICS & VISUALIZATION Graphics & Visualization: Principles & Algorithms Chapter 11 Introduction • The study of color, and the way humans perceive it, a branch of: Physics Physiology Psychology Computer Graphics Visualization • The result of graphics or visualization algorithms is a color or grayscale image to be viewed on an output device (monitor, printer) Graphics programmer should be aware of the fundamental principles behind color and its digital representation Graphics & Visualization: Principles & Algorithms Chapter 11 2 Grayscale • Intensity: achromatic light; color characteristics removed • Intensity can be represented by a real number between 0 (black) and 1 (white) Values between these two extremes are called grayscales • Assume use of d bits to represent the intensity of each pixel n=2d different intensity values per pixel • Question: which intensity values shall we represent ? • Answer: Linear scale of intensities between the minimum & maximum value, is not a good idea: Human eye perceives intensity ratios rather than absolute intensity values. Light bulb example: 20-40-60W Therefore, we opt for a logarithmic distribution of intensity values Graphics & Visualization: Principles & Algorithms Chapter 11 3 Grayscale (2) • Let Φ0 be the minimum intensity value For typical monitors: Φ0 = (1/300) * maximum value 1 (white) Such monitors have a dynamic range of 300:1 • Let λ be the ratio between successive intensity values • Then we take: Φ1 = λ* Φ0 2 Φ1 = λ* Φ1=λ *Φ0 … -
Computer Vision? Color Histograms
Lecture 11 Color © UW CSE vision faculty Starting Point: What is light? Electromagnetic radiation (EMR) moving along rays in space •R(λ) is EMR, measured in units of power (watts) – λ is wavelength Perceiving light • How do we convert radiation into “color”? • What part of the spectrum do we see? Newton’s prism experiment Newton’s own drawing of his experiment showing decomposition of white light The light spectrum We “see” electromagnetic radiation in a range of wavelengths Light spectrum The appearance of light depends on its power spectrum • How much power (or energy) at each wavelength daylight tungsten bulb Our visual system converts a light spectrum into “color” • This is a rather complex transformation Recall: Image Formation Basics i(x,y) f(x,y) r(x,y) (from Gonzalez & Woods, 2008) Image Formation: Basics Image f(x,y) is characterized by 2 components 1. Illumination i(x,y) = Amount of source illumination incident on scene 2. Reflectance r(x,y) = Amount of illumination reflected by objects in the scene f(,)(,)(,) x y i= x y r x y where 0 (< ,i ) x < y ∞andr 0 < x y ( , < ) 1 r(x,y) depends on object properties r = 0 means total absorption and 1 means total reflectance The Human Eye and Retina Color perception • Light hits the retina, which contains photosensitive cells – rods and cones • Rods responsible for intensity, cones responsible for color Density of rods and cones Rods and cones are non-uniformly distributed on the retina • Fovea - Small central region (1 or 2°) containing the highest density of cones (and no rods) • Less visual acuity in the periphery—many rods wired to the same neuron Demonstration of Blind Spot With left eye shut, look at the cross on the left. -
Colorwatch: Color Perceptual Spatial Tactile Interface for People with Visual Impairments
electronics Article ColorWatch: Color Perceptual Spatial Tactile Interface for People with Visual Impairments Muhammad Shahid Jabbar 1 , Chung-Heon Lee 1 and Jun Dong Cho 1,2,* 1 Department of Electrical and Computer Engineering, Sungkyunkwan University, Suwon 16419, Gyeonggi-do, Korea; [email protected] (M.S.J.); [email protected] (C.-H.L.) 2 Department of Human ICT Convergence, Sungkyunkwan University, Suwon 16419, Gyeonggi-do, Korea * Correspondence: [email protected] Abstract: Tactile perception enables people with visual impairments (PVI) to engage with artworks and real-life objects at a deeper abstraction level. The development of tactile and multi-sensory assistive technologies has expanded their opportunities to appreciate visual arts. We have developed a tactile interface based on the proposed concept design under considerations of PVI tactile actuation, color perception, and learnability. The proposed interface automatically translates reference colors into spatial tactile patterns. A range of achromatic colors and six prominent basic colors with three levels of chroma and values are considered for the cross-modular association. In addition, an analog tactile color watch design has been proposed. This scheme enables PVI to explore artwork or real-life object color by identifying the reference colors through a color sensor and translating them to the tactile interface. The color identification tests using this scheme on the developed prototype exhibit good recognition accuracy. The workload assessment and usability evaluation for PVI demonstrate promising results. This suggest that the proposed scheme is appropriate for tactile color exploration. Citation: Jabbar, M.S.; Lee, C.-H.; Keywords: color identification; tactile perception; cross modular association; universal design; Cho, J.D. -
Evaluating Color Gamut of Smartphone Display
Evaluating Color Gamut of Smartphone Display Introduction gamut, but the most common reference spaces used for display products are CIE Yxy (1931) and CIE Lu’v’ With increased image and video content available over (1976) chromaticity chart. the internet, there is now a growing emphasis on color fidelity and accuracy of display used in smartphone. One reason for this growing emphasis is the emergence of online merchandising. Consumers want to be sure that the colors they see on their smartphone display are actually what they will get eventually. Another reason is CIE Yxy (1931) chromaticity chart that we are now accustomed to seeing displays which are able to reproduce colors we see in the real world. Anything less, the smartphone display would be deemed as mediocre. The good news is color fidelity and accuracy of display have improved throughout the years due to better display technology, advanced signal processing and color management solution. To ensure displays are able to portray specific colors accurately, evaluating parameter like color gamut is CIE Lu’v’ (1976) chromaticity chart necessary. Apart from color gamut, parameters like white point and gamma are also of equal importance TThere are various color gamut standards drafted for in evaluating the visual characteristic of display. expressing color display range according to different industry and different application. For smartphone What is Color Gamut? and PC displays, the standard gamut is sRGB/ Rec.709. However, with the growing adoption of wide color Color gamut is defined as the range of colors that a gamut solutions in the high-end display market, wide display can reproduce. -
An Integrative Framework for the Appraisal of Coloration in Nature Author(S): Darrell J
The University of Chicago An Integrative Framework for the Appraisal of Coloration in Nature Author(s): Darrell J. Kemp, Marie E. Herberstein, Leo J. Fleishman, John A. Endler, Andrew T. D. Bennett, Adrian G. Dyer, Nathan S. Hart, Justin Marshall, Martin J. Whiting Source: The American Naturalist, Vol. 185, No. 6 (June 2015), pp. 705-724 Published by: The University of Chicago Press for The American Society of Naturalists Stable URL: http://www.jstor.org/stable/10.1086/681021 . Accessed: 07/10/2015 01:10 Your use of the JSTOR archive indicates your acceptance of the Terms & Conditions of Use, available at . http://www.jstor.org/page/info/about/policies/terms.jsp . JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact [email protected]. The University of Chicago Press, The American Society of Naturalists, The University of Chicago are collaborating with JSTOR to digitize, preserve and extend access to The American Naturalist. http://www.jstor.org This content downloaded from 23.235.32.0 on Wed, 7 Oct 2015 01:10:39 AM All use subject to JSTOR Terms and Conditions vol. 185, no. 6 the american naturalist june 2015 Synthesis An Integrative Framework for the Appraisal of Coloration in Nature Darrell J. Kemp,1,* Marie E. Herberstein,1 Leo J. Fleishman,2 John A. Endler,3,4 Andrew T.