ASTM E2214-2008 Standard Practice for Specifying and Verifying the Performance of Color-Measuring Instruments.pdf

1、Designation: E 2214 08Standard 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:4D 2244 Practice for Calculation of Color Tolerances andColor Differences from Instrumentally Measured ColorCoordinatesE 284 Terminology of AppearanceE 1164 Practice for Obtaining Spectrom

10、etric Data forObject-Color Evaluation2.2 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-sults63. Terminology3.1 Definitions of appearance terms in Termin

11、ology E 284are applicable to this pracitce.1This 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 Jan. 1, 2008. Published January 2008. Originallyapproved i

12、n 2002. Last previous edition approved in 2002 as E 2214 - 02.2Ladson, J., “Colorimetric Data Comparison of Bench-Top and PortableInstruments,” AIC Interim Meeting, Colorimetry, Berlin, 1995.3Rich, D., “Standardized Terminology and Procedures for Specifying andVerifying the Performance of Spectrocol

13、orimeters,” AIC Color 97 Kyoto, Kyoto1997.4For 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 ASTM website.5ISO/IDE/OIML/BIPM,

14、 International Vocabulary 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. Gov

15、ernment Printing Office, Washington, D. C., 1984.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.2 Definitions of metrology terms in ISO, InternationalVocabulary of Basic and General Terms in Metrology (VIM)are applicable to this p

16、ractice.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 interference filter or wedge or tunable or discreteseries of monochromatic sources), that is normally capable ofprodu

17、cing as output 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.3.3.1.1 DiscussionAt one time, UV-VIS analytical spec-trophotometers were used for colorim

18、etric measurements. To-day, while instruments intended for use in color measurementsshare many common components with UV-VIS analyticalspectrometers, there are two distinct classes of instruments.UV-VIS analytical spectrometers are designed to optimize theiruse in chemometric quantitative analysis,

19、which requires veryprecise spectral position and very narrow spectral windows andmoderate baseline stability. Colorimetric spectrometers aredesigned to optimize their use as simulations of the visualcolorimeter or as the source of spectral and colorimetricinformation for computer-assisted color matc

20、hing 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 form of reproduc-ibility in which two or more instruments from the samemanufacturer and model are compared.3.3.3 inter-m

21、odel 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 DiscussionModern instruments have such highprecision that small differences in geometric and spectraldesign can result

22、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 uncertainty of the instrumentand within the requirements of any international standard.3.3.4 mean color differe

23、nce 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 readings and the average of that setof readings. MCDM = average(DEi(average(Lab)Labi), fori =1toN readings. Any st

24、andard 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 practice defines standardized terms for the mostcommon instrument measurement performance parameters(repeatability, repr

25、oducibility, 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 instruments verify or certifythe specification and performance of color-measuring instru-ments. Following

26、this practice can improve communicationsbetween instrument manufacturers and instrument users andbetween suppliers and purchasers of colored materials.5. Significance and Use5.1 In todays commerce, instrument makers and instrumentusers must deal with a large array of bench-top and portablecolor-meas

27、uring instruments, many with different geometricand spectral characteristics.At the same time, manufacturers ofcolored goods are adopting quality management systems thatrequire periodic verification of the performance of the instru-ments that are critical to the quality of the final product. Thetech

28、nology 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. What had been a tool for the research laboratoryis now available to the retail point of sale, to manufacturi

29、ng, todesign and to corporate communications. New documentarystandards have been published that encourage the use ofcolorimeters, spectrocolorimeters, and colorimetric spetrom-eters in applications previously dominated by visual expertiseor by filter densitometers.7Therefore, it is necessary todeter

30、mine 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 some commoninstrumental parameters that relate to the way an instrumentwill contribute to the quality and

31、 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 test reportsto aid in verifying the performance of the instrument relative toits intended application.6. Inst

32、rument Performance Parameters6.1 Repeatability is generally the most important specifica-tion in a color-measuring instrument. Colorimetry is primarilya relative or differential measurement, not an absolute mea-surement. In colorimetry, there is always a standard and a trialspecimen. The standard ma

33、y 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 colorimetry is generally a test of how well theinstrument repeats its readings of the same or nearly the samespecimen over

34、 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 standarddeviation is an estimate of repeatability. Repeatability is furtherdefined as the standard deviation of a set of measurementstaken ove

35、r 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 ISOexplicitly defines the metric of “closeness of agreement” as thesample standard deviation. Since color is a multidimensional7ISO 13

36、655 Spectral Measurement and Colorimetric Computation for GraphicArts Images, International Organization for Standardization, Geneva, Switzerland.E2214082property of a material, repeatability should be reported in termsof the multidimensional variancecovariance matrix.6.1.2 The time period over whic

37、h 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 of test results.6.1.2.1 For the purposes of color

38、imetry, “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” term is normally defined as, at least theperiod of

39、 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 period of 314 years.86.2 Reproducibility is the seco

40、nd 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 different, theprocedures or instrument are different, or

41、 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 ofrepeatability in which either the time frame is

42、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-ments taken over a specified period of time by a sing

43、leoperator, 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 is a multidimensional property of a material, repr

44、oduc-ibility should be reported in terms of the multidimensionalvariancecovariance 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

45、 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 readings.6.3 Inter-Instrument Agreement, as defined in 3.3.2, de-scribes the reproducibility between two or more instruments, o

46、fidentical 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 this situation,such a test measures the consistency of the design andmanufacturing process. Within the technical description of

47、 thestandard geometric and spectral parameters for the measure-ment 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

48、 ofreference materials. The most common form of test forinter-model 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

49、, 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. If a group of instruments are being testedthen a multivariate analysis of variance (MANOVA) can beperformed to test the agreement o