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The Ideal Lovibond Color System for C I E Standard Illuminants a and C Shown in Three Colorimetric Systems

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The Ideal Lovibond Color System for C I E Standard Illuminants a and C Shown in Three Colorimetric Systems E lEFERENCi UNITED STATES \ EPARTMENT OF iOMMERCE NBS TECHNICAL NOTE 716 UBUCATION ir J V s **rts o* w The Ideal Lovibond Color System for CI Standard llluminants A and C Shown in Three U.S. RTMENT Colorimetric Systems OF )MMERCE National n , loo J0S153 197a LaJ NATIONAL BUREAU OF STANDARDS 1 The National Bureau of Standards was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology and facilitate their effective application for public benefit. To this end, the Bureau conducts research and provides: (1) a basis for the Nation's physical measure- ment system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology, the Center for Computer Sciences and Technology, and the Office for Information Programs. THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the United States of a complete and consistent system of physical measurement; coordinates that system with measurement systems of other nations; and furnishes essential services leading to accurate and uniform physical measurements throughout the Nation's scien- tific community, industry, and commerce. The Institute consists of a Center for Radia- tion Research, an Office of Measurement Services and the following divisions: Applied Mathematics—Electricity—Heat—Mechanics—Optical Physics—Linac Radiation 2—Nuclear Radiation 2—Applied Radiation 2—Quantum Electronics 3— Electromagnetics 3—Time and Frequency 3 —Laboratory Astrophysics 3—Cryo- 3 genics . THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research lead- ing to improved methods of measurement, standards, and data on the properties of well-characterized materials needed by industry, commerce, educational institutions, and Government; provides advisory and research services to other Government agencies; and develops, produces, and distributes standard reference materials. The Institute con- sists of the Office of Standard Reference Materials and the following divisions: Analytical Chemistry—Polymers—Metallurgy—Inorganic Materials—Reactor Radiation—Physical Chemistry. THE INSTITUTE FOR APPLIED TECHNOLOGY provides technical services to pro- mote the use of available technology and to facilitate technological innovation in indus- try and Government; cooperates with public and private organizations leading to the development of technological standards (including mandatory safety standards), codes and methods of test; and provides technical advice and services to Government agencies upon request. The Institute also monitors NBS engineering standards activities and provides liaison between NBS and national and international engineering standards bodies. The Institute consists of the following divisions and offices: Engineering Standards Services—Weights and Measures—Invention and Innovation—Product Evaluation Technology—Building Research—Electronic Technology—Technical Analysis—Measurement Engineering—Office of Fire Programs. THE CENTER FOR COMPUTER SCIENCES AND TECHNOLOGY conducts re- search and provides technical services designed to aid Government agencies in improv- ing cost effectiveness in the conduct of their programs through the selection, acquisition, and effective utilization of automatic data processing equipment; and serves as the prin- cipal focus within the executive branch for the development of Federal standards for automatic data processing equipment, techniques, and computer languages. The Center consists of the following offices and divisions: Information Processing Standards—Computer Information—Computer Services —Systems Development—Information Processing Technology. THE OFFICE FOR INFORMATION PROGRAMS promotes optimum dissemination and accessibility of scientific information generated within NBS and other agencies of the Federal Government; promotes the development of the National Standard Reference Data System and a system of information analysis centers dealing with the broader aspects of the National Measurement System; provides appropriate services to ensure that the NBS staff has optimum accessibility to the scientific information of the world, and directs the public information activities of the Bureau. The Office consists of the following organizational units: Office of Standard Reference Data—Office of Technical Information and Publications—Library—Office of International Relations. 1 Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washing- ton, D.C. 20234. 2 Part of the Center for Radiation Research. 3 Located at Boulder, Colorado 80302. '"' "\UC MAY 1 6 1972 The Ideal Lovibond Color System "%%i for C I E Standard llluminants A and C Shown in Three Colorimetric Systems Geraldine W. Haupt, John C. Schleter, and Kenneth L. Eckerle Heat Division Institute for Basic Standards National Bureau of Standards Washington, D.C. 20234 *t« T 0F c„ \ _-&£. 9*^ ** •"•ea^ o* U.S. DEPARTMENT OF COMMERCE, Peter G. Peterson, Secretary \j^ NATIONAL BUREAU OF STANDARDS, Lewis M. Branscomb, Director, Issued April 1972 "tT^Knir.J (^ €. m , W„ National Bureau of Standards Technical Note 716 Nat. Bur. Stand. (U.S.), Tech. Note 716, 115 pages ( Apr. 1972) CODEN: NBTNAE Issued April 1972 For sale by the Superintendent of Documents, U.S. Government Printing Office Washintgon, DC. 20402 (Order by SD Catalog No. C 13.46:716). Price $1.00. The Ideal Lovibond Color System for CIE Standard Illuminants A and C Shown in Three Colorimetric Systems Geraldine W. Haupt, John C. Schleter, and Kenneth L. Eckerle Tables are given which list luminous internal trans- mittances, luminous transmittances, and chromaticity coordinates of the ideal Lovibond color system for CIE standard illuminants A and C according to (1) the CIE 1931 (x,y)-system, (2) the CIE 1960 uniform-chromaticity-scale (UCS) (u,v) -system, and (3) the CIE 1964 (U*, V*, W*,)~ system. Chromaticity diagrams for the (x,y)- and (u,v)- systems are shown together with horizontal and vertical cross-sections of the (U*, V*, W*) -color solid for the entire ideal Lovibond color system produced by single- color units and two-color combinations of units for each illuminant. In addition, chromaticity diagrams and cross-sections are shown indicating the single-color units of red, yellow, and blue for each CIE system and illuminant, Key words: Chromaticity, Lovibond; CIE and Lovibond; color, Lovibond; color imetry, Lovibond; glass color standards; Lovibond and CIE. Lovibond glasses were introduced into this country from England at the turn of the century for the purpose of grading vegetable- and cottonseed - oils, i.e., of determining their quality and salability. These glasses together with the Lovibond Tintometer were developed in 1887 by Joseph W. Lovibond. Sets of Lovibond glasses were first made available as color standards sometime after 1896 when the company, The Tintometer Ltd. , was organized. This Lovibond color system consists of three scales, each represented by a series of glasses; a red, a yellow and a blue. The scales have been calibrated in arbitrary units, but the three units are related in such a way that for daylight illumination a combination of the same number of units of each of the red, yellow, and blue glasses results in an approximately neutral filter. Each glass in the series is identified by the number of unit glasses to which it is equivalent. In the 1920' s, the NBS undertook the standardization of one set of Lovibond glasses at the request of those interested in the use of similar glasses in the vegetable- and cottonseed-oil trade. The need or desire for an ideal scale had arisen long before 1927 when the first NBS paper on the Lovibond Color System was published [1] . This paper included, along with tables and graphs showing the fundamental spectro- photometry data for some of the glasses of NBS set BS9940 (purchased in 1912), a prefatory statement by Irwin G. Priest, first Chief of the 1 Figures in brackets indicate the literature references at on page 11. Colorimetry and Spectrophotometry Section of the National Bureau of Standards. It was here that Priest first alluded to the ideal scale by stating as one of the objectives of that standardization: "2. To specify in reproducible colorimetric terms a standard Lovibond scale which shall represent the present actual colors (BS9940) as closely as possible, subject to the condition that the irregularities or erratic variations (which are obviously departures from what might be called an ideal scale) are eliminated". These obvious departures may be seen in figures 1 and 2 of the paper published in 1947 [2]. These Lovibond "network" graphs were prepared to supply additional colorimetric data about the set BS9940. In 1962, the ideal units for the red (R) , yellow (Y) , and blue (B) glasses of the Lovibond Color System were defined in the paper by Judd, Chamberlin, and Haupt, "The Ideal Lovibond System" [3]. Table I of the 1962 paper gives the spectral internal transmittances of each of the unit glasses defining the ideal Lovibond Color System. These trans- mittances are based on fundamental spectrophotometric data determined for 20 glasses of each series (1, 2, 3, ..., 20). Some of the data were obtained at the NBS for the glasses of set BS9940 and others were obtained by the Tintometer, Ltd. , for glasses retained
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