1、Designation: E 2214 02Standard Practice forSpecifying and Verifying the Performance of Color-Measuring Instruments1This standard is issued under the fixed designation E 2214; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、 of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.INTRODUCTIONRecent advances in optics, electronics and documentary standard have resulted in a proliferation ofinstruments fo
3、r 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 standar
4、ds 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.2,3F
5、ollowing 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
6、.1. 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 forma
7、t and 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
8、 and 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 an
9、d determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:D 2244 Practice for Calculation of Color Tolerances andColor Differences from Instrumentally Measured ColorCoordinates4E 284 Terminology of Appearance4E 1164 Practice for Obtaining Spectro
10、photometric Data forObject-Color Evaluation42.2 Other Documents:ISO International Vocabulary of Basic and General Terms inMetrology (VIM)5NIST Technical Note 1297 Guidelines for Evaluating andExpressing the Uncertainty of NIST Measurement Re-sults6DIN 55600 Bestimmung der Signifikanz von Farbabstnde
11、n1This 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 June 10, 2002. Published August 2002.2Ladson, J., “Colorimetric Data Comparison of Bench-Top and Por
12、tableInstruments,” AIC Interim Meeting, Colorimetry, Berlin, 1995.3Rich, D., “Standardized Terminology and Procedures for Specifying andVerifying the Performance of Spectrocolorimeters,” AIC Color 97 Kyoto, Kyoto1997.4Annual Book of ASTM Standards, Vol 06.01.5ISO/IDE/OIML/BIPM, International Vocabul
13、ary of Basic and General Termsin Metrology, International Organization for Standardization, Geneva, Switzerland,1984.6Taylor, Barry N., and Kuyatt, Chris E., Guidelines for Evaluating andExpressing the Uncertainty of NIST Measurement Results, NIST Technical Note1297, U. S. Government Printing Office
14、, Washington, D. C., 1984.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.bei Krperfarben nach der CIELAB-Formel73. Terminology3.1 Definitions of appearance terms in Terminology E 284are applicable to this pracitce.3.2 Definitions of
15、 metrology terms in ISO, InternationalVocabulary of Basic and General Terms in Metrology (VIM)are applicable to this practice.3.3 Definitions 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
16、 interference filter or wedge or tunable or discreteseries of monochromatic sources), that is normally capable ofproducing as output colorimetric data (such as tristimulusvalues and derived color coordinates or indices of appearanceattributes) as well as the underlying spectral data from whichthe co
17、lorimetric data are derived.3.3.1.1 DiscussionAt one time, UV-VIS analytical spec-trophotometers were used for colorimetric measurements. To-day, while instruments intended for use in color measurementsshare many common components with UV-VIS analyticalspectrometers, there are two distinct classes o
18、f instruments.UV-VIS analytical spectrometers are designed to optimize theiruse in chemometric quantitative analysis, which requires veryprecise spectral position and very narrow spectral windows andmoderate baseline stability. Colorimetric spectrometers aredesigned to optimize their use as simulati
19、ons of the visualcolorimeter or as the source of spectral and colorimetricinformation for computer-assisted color matching systems.They allow more tolerance on the spectral scale and spectralwindow width but demand much more stability in the radio-metric scale.3.3.2 inter-instrument agreement, na fo
20、rm of reproduc-ibility in which two or more instruments from the samemanufacturer and model are compared.3.3.3 inter-model agreement, na form of reproducibilityin which the measurements of two or more instruments fromdifferent manufacturers or of different but equivalent design arecompared.3.3.3.1 D
21、iscussionModern 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 co
22、mbined uncertainty 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
23、 of readings and the average of that setof readings. MCDM = average(DEi(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 D 2244).4. Summary of Practice4.1 This pr
24、actice defines 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 colo
25、r-measuring 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 t
26、odays commerce, 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 perio
27、dic verification 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 inper
28、formance. What 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
29、in applications previously dominated by visual expertiseor by filter densitometers.8Therefore, 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 des
30、criptions of 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 t
31、ests and test reportsto aid in verifying the performance of the instrument relative toits intended application.6. Instrument Performance Parameters6.1 Repeatability is generally the most important specifica-tion in a color-measuring instrument. Colorimetry is primarilya relative or differential meas
32、urement, not an absolute mea-surement. In colorimetry, there is always a standard and a trialspecimen. The standard may be a real physical specimen or itmay be a set of theoretical target values. The trial is usuallysimilar to the standard in both appearance and spectral nature.Thus, industrial colo
33、rimetry is generally a test of how well theinstrument repeats its readings of the same or nearly the samespecimen over a period of minutes, hours, days, and weeks.6.1.1 The ISO VIM defines repeatability as a measure of therandom error of a reading and assumes that the sample standard7DIN, Deutsches
34、Institut fr Normung,-Taschenbuch 49, Farbmittel 1, Pgimente,Fllstoffe, Farbstoffe, DIN 5033 Teil 1 bis DIN 55929, Beuth Verlag GmbH, Berlin.8ISO 13655 Spectral Measurement and Colorimetric Computation for GraphicArts Images, International Organization for Standardization, Geneva, Switzerland.E221402
35、2deviation is an estimate of repeatability. Repeatability is furtherdefined as the standard deviation of a set of measurementstaken over a specified time period by a single operator, on asingle instrument with a single specimen. This definition issimilar to that in Terminology E 284, except that the
36、 ISOexplicitly defines the metric of “closeness of agreement” as thesample standard deviation. Since color is a multidimensionalproperty of a material, repeatability should be reported in termsof the multidimensional standard deviations, derived from thesquare root of the absolute value of the varia
37、ncecovariancematrix.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 these timeframes do not overlap. This is intentional, providing clearlydefined milestones in the temporal stability
38、 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 time will vary as afunction of lamp and power supply characteristics but shouldbe less than one hour.6.1.2.2 “Medium”
39、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 readings taken over a period of at least 4 to 8 weeks.The longest known reported study described readings takenover a pe
40、riod of 314 years.96.2 Reproducibility is the second most important specifica-tion in a color-measuring instrument. According to Terminol-ogy E 284, reproducibility is a form of repeatability in whichone or more of the measurement parameters have beensystematically changed. Thus the sample is differ
41、ent, theprocedures or instrument are different, or the time frame is verylong. The increase of disorder over a very long time changesthe instrument systematically and the set of readings reallycompares a “young” instrument with an “old” instrument.6.2.1 The ISO VIM defines reproducibility as a type
42、ofrepeatability in which either the time frame is very long, inwhich the operator changes, the instrument changes, or themeasurement conditions change. ISO again recommends esti-mating this with a standard deviation. Reproducibility isfurther defined as the standard deviation of a set of measure-men
43、ts taken over a specified period of time by a singleoperator, on a single instrument with a single specimen. Thisdefinition is similar to that in Terminology E 284, except thatthe ISO again, explicitly defines the metric of “closeness ofagreement” as the sample standard deviation. Again, sincecolor
44、is a multidimensional property of a material, reproduc-ibility should be reported in terms of the multidimensionalstandard deviations, derived from the square root of theabsolute value of the variancecovariance matrix.6.2.2 The time period over which the readings are collectedmust be specified. For
45、the purposes of colorimetry, “long” termrepeatability is the most common and important type ofreproducibility. Repeatability and reproducibility have tradi-tionally been evaluated in colorimetry by comparing the colordifferences of a set of readings to a single reading or to theaverage of the set of
46、 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 a concept. This is because in most test results, a methodor instrument dependent bias can be assessed. In
47、 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 of diffuse reflectance factor and color, a significantamount of latitude exists. This latitude results i
48、n 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 instrument agreement is pairwise color differenceassessment of a series of specimens. Various parameters
49、 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 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. I
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