ASTM E2214-2018 Standard Practice for Specifying and Verifying the Performance of Color-Measuring Instruments.pdf

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1、Designation: E2214 17E2214 18Standard Practice forSpecifying and Verifying the Performance of Color-Measuring Instruments1This standard is issued under the fixed designation E2214; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, th

2、e year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.INTRODUCTIONRecent advances in optics, electronics and documentary standard have resulted in a proliferation ofinstrumen

3、ts for the measurement of color and appearance of materials and objects. These instrumentspossess very good performance but there has been little progress toward standardizing the terminologyand procedures to quantify that performance. Therefore, the commercial literature and even somedocumentary st

4、andards are a mass of confusing terms, numbers and specifications that are impossibleto compare or interpret.Two recent papers in the literature, have proposed terms and procedures to standardize thespecification, comparison and verification of the level of performance of a color-measuringinstrument

5、.2,3 Following those procedures, those specifications can be compared to product tolerances.This becomes important so that instrument users and instrument makers can agree on how to compareor verify, or both, that their instruments are performing in the field as they were designed and testedin the f

6、actory.1. Scope1.1 This practice provides standard terms and procedures for describing and characterizing the performance of spectral and filterbased instruments designed to measure and compute the colorimetric properties of materials and objects. It does not set thespecifications but rather gives t

7、he format and process by which specifications can be determined, communicated and verified.1.2 This practice does not describe methods that are generally applicable to visible-range spectroscopic instruments used foranalytical chemistry (UV-VIS spectrophotometers). ASTM Committee E13 on Molecular Sp

8、ectroscopy and Chromatographyincludes such procedures in standards under their jurisdiction.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety safety, health,

9、and healthenvironmental practices and determine theapplicability of regulatory limitations prior to use.1.4 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of Internatio

10、nal Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:4D2244 Practice for Calculation of Color Tolerances and Color Differences from Instrumentally Measured Color CoordinatesE284 Terminolo

11、gy of AppearanceE1164 Practice for Obtaining Spectrometric Data for Object-Color Evaluation1 This practice is under the jurisdiction of ASTM Committee E12 on Color and Appearance and is the direct responsibility of Subcommittee E12.04 on Color andAppearance Analysis.Current edition approved May 1, 2

12、017Oct. 15, 2018. Published July 2017October 15, 2018. Originally approved in 2002. Last previous edition approved in 20162017 asE2214 16.E2214 17. DOI: 10.1520/E2214-17.10.1520/E2214-18.2 Ladson, J., “Colorimetric Data Comparison of Bench-Top and Portable Instruments,” AIC Interim Meeting, Colorime

13、try, Berlin, 1995.3 Rich, D., “Standardized Terminology and Procedures for Specifying and Verifying the Performance of Spectrocolorimeters,” AIC Color 97 Kyoto, Kyoto, 1997.4 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For An

14、nual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not b

15、e technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Driv

16、e, PO Box C700, West Conshohocken, PA 19428-2959. United States12.2 Other Documents:ISO VIM International Vocabulary of Basic and General Terms in Metrology (VIM)5NIST Technical Note 1297 Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results63. Terminology3.1 Definitio

17、ns of appearance terms in Terminology E284 are applicable to this practice.3.2 Definitions of metrology terms in ISO, International Vocabulary of Basic and General Terms in Metrology (VIM) areapplicable to this practice.3.3 Definitions of Terms Specific to This Standard:3.3.1 colorimetric spectromet

18、er, nspectrometer, one component of which is a dispersive element (such as a prism, grating orinterference filter or wedge or tunable or discrete series of monochromatic sources), that is normally capable of producing as outputcolorimetric data (such as tristimulus values and derived color coordinat

19、es or indices of appearance attributes) as well as theunderlying spectral data from which the colorimetric data are derived.3.3.2 inter-instrument agreement, nthe closeness of agreement between the results of measurements in which two or moreinstruments from the same manufacturer and model are compa

20、red.3.3.3 inter-model agreement, nthe closeness of agreement between the results of measurements in which two or moreinstruments from different manufacturers, or of different but equivalent design, are compared.3.3.3.1 DiscussionModern instruments have such high precision that small differences in g

21、eometric and spectral design can result in significantdifferences in the performance of two instruments. This can occur even though both instruments exhibit design and performancebias which are well within the expected combined uncertainty of the instrument and within the requirements of any interna

22、tionalstandard.3.3.4 mean color difference from the mean, MCDM, na measure of expectation value of the performance of a color-measuringinstrument.3.3.4.1 DiscussionMCDM calculates the average color difference between a set of readings and the average of that set of readings. MCDM =average(Ei(average

23、(Lab) Labi), for i = 1 to N readings. Any standard color difference or color tolerance equation can be usedas long as the report clearly identifies the equation being used (see Practice D2244).4. Summary of Practice4.1 This practice defines standardized terms for the most common instrument measureme

24、nt performance parameters(repeatability, reproducibility, inter-instrument agreement, inter-model instrument agreement, accuracy) and describes a set ofmeasurements and artifacts, with which both the producers and users of color-measuring instruments verify or certify thespecification and performanc

25、e of color-measuring instruments. Following this practice can improve communications betweeninstrument manufacturers and instrument users and between suppliers and purchasers of colored materials.5. Significance and Use5.1 In todays commerce, instrument makers and instrument users must deal with a l

26、arge array of bench-top and portablecolor-measuring instruments, many with different geometric and spectral characteristics. At the same time, manufacturers ofcolored goods are adopting quality management systems that require periodic verification of the performance of the instrumentsthat are critic

27、al to the quality of the final product. The technology involved in optics and electro-optics has progressed greatly overthe last decade. The result has been a generation of instruments that are both more affordable and higher in performance. Whathad been a tool for the research laboratory is now ava

28、ilable to the retail point of sale, to manufacturing, to design and to corporatecommunications. New documentary standards have been published that encourage the use of colorimeters, spectrocolorimeters,and colorimetric spetrometers in applications previously dominated by visual expertise or by filte

29、r densitometers.7 Therefore, it isnecessary to determine if an instrument is suitable to the application and to verify that an instrument or instruments are workingwithin the required operating parameters.5 ISO/IDE/OIML/BIPM, International Vocabulary of Basic and General Terms in Metrology, Internat

30、ional Organization for Standardization, Geneva, Switzerland, 1984.6 Taylor, Barry N., and Kuyatt, Chris E., Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results, NIST Technical Note 1297, U. S.Government Printing Office, Washington, D. C., 1984.7 ISO 13655 Spectral Me

31、asurement and Colorimetric Computation for Graphic Arts Images, International Organization for Standardization, Geneva, Switzerland.E2214 1825.2 This practice provides descriptions of some common instrumental parameters that relate to the way an instrument willcontribute to the quality and consisten

32、cy of the production of colored goods. It also describes some of the material standardsrequired to assess the performance of a color-measuring instrument and suggests some tests and test reports to aid in verifying theperformance of the instrument relative to its intended application.6. Instrument P

33、erformance Parameters6.1 Repeatabilityis generally the most important specification in a color-measuring instrument. Colorimetry is primarily arelative or differential measurement, not an absolute measurement. In colorimetry, there is always a standard and a trial specimen.The standard may be a real

34、 physical specimen or it may be a set of theoretical target values. The trial is usually similar to thestandard in both appearance and spectral nature. Thus, industrial colorimetry is generally a test of how well the instrument repeatsits readings of the same or nearly the same specimen over a perio

35、d of minutes, hours, days, and weeks.6.1.1 The ISO VIM defines repeatability as a measure of the random error of a reading and assumes that the sample standarddeviation is an estimate of repeatability. Repeatability is further defined as the standard deviation of a set of measurements takenover a sp

36、ecified time period by a single operator, on a single instrument with a single specimen. This definition is similar to thatin Terminology E284, except that the ISO explicitly defines the metric of “closeness of agreement” as the sample standarddeviation. Since color is a multidimensional property of

37、 a material, repeatability should be reported in terms of themultidimensional variancecovariance matrix.matrix, or in terms of the 95 % confidence interval of its combinatorial colordifference for a single specimen. See 6.6.6.1.2 The time period over which the readings are collected must be specifie

38、d and is often qualitatively described as “short,”“medium,” or “long.” The definitions of these time frames do not overlap. This is intentional, providing clearly defined milestonesin the temporal stability of test results.6.1.2.1 For the purposes of colorimetry, “short” is normally the time require

39、d to collect a set of 30 readings, taken as fast asthe instrument will allow. The actual time will vary as a function of lamp and power supply characteristics but should be less thanone hour.6.1.2.2 “Medium” term is normally defined as, at least the period of one work shift (8 h) but less than three

40、 work shifts (oneday).6.1.2.3 “Long” term is open ended but is often described as any set readings taken over a period of at least 4 to 8 weeks. Thelongest known reported study described readings taken over a period of 314 years.86.2 Reproducibility is the second most important specification in a co

41、lor-measuring instrument. According to TerminologyE284, reproducibility is the closeness of agreement of the results of measurements in which one or more of the measurementparameters have been systematically changed. Thus the sample is different, the procedures or instrument are different, or the ti

42、meframe is very long. The increase of disorder over a very long time changes the instrument systematically and the set of readingsreally compares a “young” instrument with an “old” instrument.6.2.1 The ISO VIM defines reproducibility as the closeness of agreement of the results of measurements in wh

43、ich either the timeframe is very long, in which the operator changes, the instrument changes, or the measurement conditions change. ISO againrecommends estimating this with a standard deviation. Reproducibility is further defined as the standard deviation of a set ofmeasurements taken over a specifi

44、ed period of time by a single operator, on a single instrument with a single specimen. Thisdefinition is similar to that in Terminology E284, except that the ISO again, explicitly defines the metric of “closeness ofagreement” as the sample standard deviation. Again, since color is a multidimensional

45、 property of a material, reproducibilityshould be reported in terms of the multidimensional variancecovariance matrix.6.2.2 The time period over which the readings are collected must be specified. For the purposes of colorimetry, “long” termrepeatability is the most common and important type of repr

46、oducibility. Repeatability and reproducibility have traditionally beenevaluated in colorimetry by comparing the color differences of a set of readings to a single reading or to the average of the set ofreadings.6.3 Inter-Instrument Agreement, as defined in 3.3.2, describes the reproducibility betwee

47、n two or more instruments, of identicaldesign. The ISO has no definition or description of such a concept. This is because in most test results, a method or instrumentdependent bias can be assessed. In this situation, such a test measures the consistency of the design and manufacturing process.Withi

48、n the technical description of the standard geometric and spectral parameters for the measurement of diffuse reflectance factorand color, a significant amount of latitude exists. This latitude results in a random amount of bias. For a given design, amanufacturer may reduce the random bias, often to

49、a level less than the stability of reference materials. The most common formof test for inter-model instrument agreement is pairwise color difference assessment of a series of specimens. Various parametersare reported in the literature including the average color difference, the maximum color difference, the typical color difference, theRMS color difference or the MCDM mean color difference from the mean, taking the average of all instruments as the standardand the other as the test instrument. Using pairs of instruments and materials one can derive a multivariate