ASTM E2214-17 Standard Practice for Specifying and Verifying the Performance of Color-Measuring Instruments.pdf

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1、Designation: E2214 17Standard 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, the year o

2、f 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 ofinstruments for t

3、he 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 standards

4、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.2,3Foll

5、owing 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 factory.1.

6、 Scope1.1 This practice provides standard terms and proceduresfor describing and characterizing the performance of spectraland filter based instruments designed to measure and computethe colorimetric properties of materials and objects. It does notset the specifications but rather gives the format a

7、nd process bywhich specifications can be determined, communicated andverified.1.2 This practice does not describe methods that are gener-ally applicable to visible-range spectroscopic instruments usedfor analytical chemistry (UV-VIS spectrophotometers). ASTMCommittee E13 on Molecular Spectroscopy an

8、d Chromatog-raphy includes such procedures in standards under their juris-diction.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and d

9、etermine the applica-bility of regulatory limitations prior to use.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-men

10、dations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:4D2244 Practice for Calculation of Color Tolerances andColor Differences from Instrumentally Measured ColorCoordinatesE284 Terminology of AppearanceE1164 Practice for O

11、btaining Spectrometric Data for Object-Color Evaluation1This practice is under the jurisdiction of ASTM Committee E12 on Color andAppearance and is the direct responsibility of Subcommittee E12.04 on Color andAppearance Analysis.Current edition approved May 1, 2017. Published July 2017. Originally a

12、pprovedin 2002. Last previous edition approved in 2016 as E2214 16. DOI: 10.1520/E2214-17.2Ladson, J., “Colorimetric Data Comparison of Bench-Top and PortableInstruments,” AIC Interim Meeting, Colorimetry, Berlin, 1995.3Rich, D., “Standardized Terminology and Procedures for Specifying andVerifying t

13、he Performance of Spectrocolorimeters,” AIC Color 97 Kyoto, Kyoto,1997.4For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe AST

14、M website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopmen

15、t of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.12.2 Other Documents:ISO VIM International Vocabulary of Basic and GeneralTerms in Metrology (VIM)5NIST Technical Note 1297 Guidelines for Evaluating andExpress

16、ing the Uncertainty of NIST Measurement Re-sults63. Terminology3.1 Definitions of appearance terms in Terminology E284are applicable to this practice.3.2 Definitions of metrology terms in ISO, InternationalVocabulary of Basic and General Terms in Metrology (VIM)are applicable to this practice.3.3 De

17、finitions of Terms Specific to This Standard:3.3.1 colorimetric spectrometer, nspectrometer, one com-ponent of which is a dispersive element (such as a prism,grating or interference filter or wedge or tunable or discreteseries of monochromatic sources), that is normally capable ofproducing as output

18、 colorimetric data (such as tristimulusvalues and derived color coordinates or indices of appearanceattributes) as well as the underlying spectral data from whichthe colorimetric data are derived.3.3.2 inter-instrument agreement, nthe closeness of agree-ment between the results of measurements in wh

19、ich two ormore instruments from the same manufacturer and model arecompared.3.3.3 inter-model agreement, nthe closeness of agreementbetween the results of measurements in which two or moreinstruments from different manufacturers, or of different butequivalent design, are compared.3.3.3.1 DiscussionM

20、odern instruments have such highprecision that small differences in geometric and spectraldesign can result in significant differences in the performanceof two instruments. This can occur even though both instru-ments exhibit design and performance bias which are wellwithin the expected combined unc

21、ertainty of the instrumentand within the requirements of any international standard.3.3.4 mean color difference from the mean, MCDM, nameasure of expectation value of the performance of a color-measuring instrument.3.3.4.1 DiscussionMCDM calculates the average colordifference between a set of readin

22、gs and the average of that setof readings. MCDM = average(Ei(average(Lab)Labi), fori =1toN readings. Any standard color difference or colortolerance equation can be used as long as the report clearlyidentifies the equation being used (see Practice D2244).4. Summary of Practice4.1 This practice defin

23、es standardized terms for the mostcommon instrument measurement performance parameters(repeatability, reproducibility, inter-instrument agreement,inter-model instrument agreement, accuracy) and describes aset of measurements and artifacts, with which both the produc-ers and users of color-measuring

24、instruments verify or certifythe specification and performance of color-measuring instru-ments. Following this practice can improve communicationsbetween instrument manufacturers and instrument users andbetween suppliers and purchasers of colored materials.5. Significance and Use5.1 In todays commer

25、ce, instrument makers and instrumentusers must deal with a large array of bench-top and portablecolor-measuring instruments, many with different geometricand spectral characteristics.At the same time, manufacturers ofcolored goods are adopting quality management systems thatrequire periodic verifica

26、tion of the performance of the instru-ments that are critical to the quality of the final product. Thetechnology involved in optics and electro-optics has progressedgreatly over the last decade. The result has been a generation ofinstruments that are both more affordable and higher inperformance. Wh

27、at had been a tool for the research laboratoryis now available to the retail point of sale, to manufacturing, todesign and to corporate communications. New documentarystandards have been published that encourage the use ofcolorimeters, spectrocolorimeters, and colorimetric spetrom-eters in applicati

28、ons previously dominated by visual expertiseor by filter densitometers.7Therefore, it is necessary todetermine if an instrument is suitable to the application and toverify that an instrument or instruments are working within therequired operating parameters.5.2 This practice provides descriptions of

29、 some commoninstrumental parameters that relate to the way an instrumentwill contribute to the quality and consistency of the productionof colored goods. It also describes some of the materialstandards required to assess the performance of a color-measuring instrument and suggests some tests and tes

30、t reportsto aid in verifying the performance of the instrument relative toits intended application.6. Instrument Performance Parameters6.1 Repeatabilityis generally the most important specifi-cation in a color-measuring instrument. Colorimetry is primar-ily a relative or differential measurement, no

31、t an absolutemeasurement. In colorimetry, there is always a standard and atrial specimen. The standard may be a real physical specimenor it may be a set of theoretical target values. The trial isusually similar to the standard in both appearance and spectralnature. Thus, industrial colorimetry is ge

32、nerally a test of howwell the instrument repeats its readings of the same or nearlythe same specimen over a period of minutes, hours, days, andweeks.6.1.1 The ISO VIM defines repeatability as a measure of therandom error of a reading and assumes that the sample standarddeviation is an estimate of re

33、peatability. Repeatability is furtherdefined as the standard deviation of a set of measurementstaken over a specified time period by a single operator, on a5ISO/IDE/OIML/BIPM, International Vocabulary of Basic and General Termsin MetrologyInternational Organization for Standardization, Geneva, Switz

34、erland,1984.6TaylorBarry N., and Kuyatt, Chris E., Guidelines for Evaluating and Express-ing the Uncertainty of NIST Measurement ResultsNIST Technical Note 1297, U. S.Government Printing Office, Washington, D. C., 1984.7ISO 13655 Spectral Measurement and Colorimetric Computation for GraphicArts Imag

35、es, International Organization for Standardization, Geneva, Switzerland.E2214 172single instrument with a single specimen. This definition issimilar to that in Terminology E284, except that the ISOexplicitly defines the metric of “closeness of agreement” as thesample standard deviation. Since color

36、is a multidimensionalproperty of a material, repeatability should be reported in termsof the multidimensional variancecovariance matrix.6.1.2 The time period over which the readings are collectedmust be specified and is often qualitatively described as“short,” “medium,” or “long.” The definitions of

37、 these timeframes do not overlap. This is intentional, providing clearlydefined milestones in the temporal stability of test results.6.1.2.1 For the purposes of colorimetry, “short” is normallythe time required to collect a set of 30 readings, taken as fastas the instrument will allow. The actual ti

38、me will vary as afunction of lamp and power supply characteristics but shouldbe less than one hour.6.1.2.2 “Medium” term is normally defined as, at least theperiod of one work shift (8 h) but less than three work shifts(one day).6.1.2.3 “Long” term is open ended but is often described asany set read

39、ings taken over a period of at least 4 to 8 weeks.The longest known reported study described readings takenover a period of 314 years.86.2 Reproducibility is the second most important specifica-tion in a color-measuring instrument. According to Terminol-ogy E284, reproducibility is the closeness of

40、agreement of theresults of measurements in which one or more of the measure-ment parameters have been systematically changed. Thus thesample is different, the procedures or instrument are different,or the time frame is very long. The increase of disorder over avery long time changes the instrument s

41、ystematically and theset of readings really compares a “young” instrument with an“old” instrument.6.2.1 The ISO VIM defines reproducibility as the closenessof agreement of the results of measurements in which either thetime frame is very long, in which the operator changes, theinstrument changes, or

42、 the measurement conditions change.ISO again recommends estimating this with a standard devia-tion. Reproducibility is further defined as the standard devia-tion of a set of measurements taken over a specified period oftime by a single operator, on a single instrument with a singlespecimen. This def

43、inition is similar to that in TerminologyE284, except that the ISO again, explicitly defines the metric of“closeness of agreement” as the sample standard deviation.Again, since color is a multidimensional property of a material,reproducibility should be reported in terms of the multidimen-sional var

44、iancecovariance matrix.6.2.2 The time period over which the readings are collectedmust be specified. For the purposes of colorimetry, “long” termrepeatability is the most common and important type ofreproducibility. Repeatability and reproducibility have tradi-tionally been evaluated in colorimetry

45、by comparing the colordifferences of a set of readings to a single reading or to theaverage of the set of readings.6.3 Inter-Instrument Agreement, as defined in 3.3.2, de-scribes the reproducibility between two or more instruments, ofidentical design. The ISO has no definition or description ofsuch

46、a concept. This is because in most test results, a methodor instrument dependent bias can be assessed. In this situation,such a test measures the consistency of the design andmanufacturing process. Within the technical description of thestandard geometric and spectral parameters for the measure-ment

47、 of diffuse reflectance factor and color, a significantamount of latitude exists. This latitude results in a randomamount of bias. For a given design, a manufacturer may reducethe random bias, often to a level less than the stability ofreference materials. The most common form of test forinter-model

48、 instrument agreement is pairwise color differenceassessment of a series of specimens. Various parameters arereported in the literature including the average color difference,the maximum color difference, the typical color difference, theRMS color difference or the MCDM mean color differencefrom the

49、 mean, taking the average of all instruments as thestandard and the other as the test instrument. Using pairs ofinstruments and materials one can derive a multivariate confi-dence interval against the value 0.0 difference and then testindividual components to determine which attribute (lightness,chroma, hue) are the significant contributors to the differencesbetween instruments. If a group of instruments are being testedthen a multivariate analysis of variance (MANOVA) can beperformed to test the agreement of the means of the instrument.6.4 Inter-Model Agreem