1、Designation: D4086 92a (Reapproved 2012)Standard Practice forVisual Evaluation of Metamerism1This standard is issued under the fixed designation D4086; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A nu
2、mber in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.INTRODUCTIONBecause perceived color involves the spectral characteristics of source, object, and eye, differentcombinations of spectral characteristi
3、cs can evoke the same color sensation. For this reason,metamerism has been described as “invisible spectral differences.”Apair of specimens is said to be metameric when the specimens match under one set of illuminatingand viewing conditions and do not match under another set. For this condition to e
4、xist, there must bedifferences in spectral character of specimens and sources or specimens and observers. There may bemore than one condition under which the specimens match, as well as more than one for which theyare a mismatch. Similarly, two specimens may be a near-match under one set of conditio
5、ns, and underanother set the direction and magnitude of the color difference may change.1. Scope1.1 This practice describes visual methods for detectingmetamerism and for estimating the magnitude of a metamericcolor difference.1.2 The practice is limited to the consideration of illuminantmetamerism
6、and observer metamerism. It is not designed tocover so-called geometric metamerism, in which members ofspecimen pairs change relative appearance as the angles ofillumination and viewing are changed, for example, becausethey incorporate flake metal or pearlescent colorants.1.3 This practice does not
7、provide for the computation ofindices of metamerism based upon instrumental measurementof spectral characteristics.1.4 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
8、safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D2616 Test Method for Evaluation of Visual Color Differ-ence With a Gray Scale (Withdrawn 2012)3E284 Terminology of Appearance3. Terminology3.1 Definitions o
9、f appearance terms used in this practicemay be found in Terminology E284.3.2 Definitions:3.2.1 metamerism, nproperty of two specimens that matchunder a specified illuminator and to a specified observer andwhose spectral reflectances or transmittances differ in thevisible wavelengths.3.2.1.1 Discussi
10、onAs a consequence of the required dif-ference, the two specimens may not match under a differentilluminator or to a different observer. Similar considerationsapply to two lights matching to a specified observer but not toother observers. (E284)3.2.2 paramerism, nphenomenon in which specimenshaving
11、different spectrophotometric curves produce approxi-mately the same color sensation under the same illuminatingand viewing conditions. (E284)4. Significance and Use4.1 Metameric color matches result from the use of differentcolorants (pigments, dyes, and the like) in achieving the samecolor match. U
12、sually, the purchaser requires that the colormatch be nonmetameric; this practice permits this requirementto be quickly tested in both field and laboratory. Where1This practice is under the jurisdiction of ASTM Committee E12 on Color andAppearance and is the direct responsibility of Subcommittee E12
13、11 on VisualMethods.Current edition approved July 1, 2012. Published August 2012. Originallyapproved in 1982. Last previous edition approved in 2007 as D4086 92a (2007).DOI: 10.1520/D4086-92AR12.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at
14、 serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohock
15、en, PA 19428-2959. United States1nonmetameric matches are not possible or practicable, for costor other reasons, some limitation of metamerism may berequired. The procedures for estimating the magnitude ofmetamerism described in this practice provide methods forassessing the effectiveness of such li
16、mitation.5. Test Specimens5.1 This practice does not cover the preparation of testspecimens. The method shall be agreed upon between thepurchaser and the seller.6. Procedure for Visual Detection of Metamerism6.1 Illuminant MetamerismAfter observing that a pair ofspecimens is a visual match under one
17、 light source, theobserver should view the specimens under one or more sourceshaving distinctly different spectral power distributions. Amongthe suggested sources are daylight, incandescent light, andfluorescent lamp light. The larger the differences in spectralcharacter of the sources, the easier i
18、t is to detect small degreesof metamerism.6.2 Observer MetamerismSpecimens that are a match toone observer under a given light source are then viewed byother normal observers under the same conditions. Typically,five to ten observers should be used so that the results are notbiased by differences am
19、ong observers within the range ofnormal color vision. Replicate judgments by each observermay also be useful. Observer metamerism is indicated whenthere is obvious disagreement among observers as to themagnitude and direction of the color difference.7. Procedures for Estimating Degrees of Metamerism
20、7.1 When the existence of metamerism has been establishedby visual evaluation of a pair of specimens, as indicated inSection 6, the degree of metamerism for that combination ofsource and observer can be determined by a visual estimate ofthe color difference. Use is made of paired gray scales, asspec
21、ified in Test Method D2616, that display increasinglylarger color differences with each successive pair of grays inthe scale. The metameric specimen pair is placed in juxtapo-sition with the edge of the gray scale and compared withvarious gray pairs. The total perceived color difference be-tween the
22、 two members of the test pair is compared to thelightness differences of the pairs on the gray scale, and the grayscale pair is selected that is the best visual equivalent to thecolor difference of the test pair. It is assumed, as in theSignificance and Use section in Test Method D2616, that, thetot
23、al color difference can be so evaluated in terms of anequivalent lightness difference. Observers can be expected toreproduce such evaluations within a half-step on the gray scale.NOTE 1Visual Evaluation of Spectral Reflectance CurvesWhenspecimens that match under one set of circumstances are measure
24、d on aspectrophotometer that produces a reflectance curve in the visual region ofthe spectrum, direct comparison of such curves will disclose if there ismetamerism. It is convenient to plot the spectral curves of the twomembers of a metameric pair on the same sheet. The curves must intersecta minimu
25、m of three times for specimens to be metameric. Specimens arenot metameric when the curves intersect only one or two times in thevisible wavelengths, or when the curves do not intersect, but are merelyproportionally higher or lower in reflectance throughout the wavelengthregion. Judgment of the degr
26、ee of metamerism by qualitative visualinspection of spectrophotometric curves requires considerable skill andexperience.8. Report8.1 Report the following information:8.1.1 Identification of the specimens,8.1.2 Procedures employed,8.1.3 Results observed in Section 6,8.1.4 Matching gray scale pair in
27、Section 7,8.1.5 Observed qualitative differences in hue, saturation,and lightness in accordance with the Procedure section, seeEvaluation of the Color Difference, of Test Method D2616,8.1.6 Number of observers and whether or not they weretested for color vision anomalies, and8.1.7 Description of lig
28、ht sources used as to type, size, colortemperature, and spectral power distribution.9. Precision and Bias9.1 PrecisionThe only quantitative portion of this prac-tice, for which consideration of precision is appropriate, isSection 7, where use is made of Test Method D2616. Theprecision statements of
29、that test method should be consulted ifD2616 is used.9.2 BiasThere are no recognized standards by which toassess the bias of this practice.10. Keywords10.1 metamerism; visual examination-color; visualexamination-metamerismASTM International takes no position respecting the validity of any patent rig
30、hts asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any
31、 time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments wi
32、ll receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by AS
33、TM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the ASTM website (www.astm.org/COPYRIGHT/).D4086 92a (2012)2
