1、Designation: D 4086 92a (Reapproved 2007)Standard Practice forVisual Evaluation of Metamerism1This standard is issued under the fixed designation D 4086; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A
2、number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) 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 characteri
3、stics 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 t
4、o exist, 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 condi
5、tions, 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 illuminantmetameri
6、sm 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 n
7、ot 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-pria
8、te safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 2616 Test Method for Evaluation of Visual Color Differ-ence With a Gray ScaleE 284 Terminology of Appearance3. Terminology3.1 Definitions of appearance
9、terms used in this practicemay be found in Terminology E 284.3.2 Definitions:3.2.1 metamerism, nproperty of two specimens thatmatch under a specified illuminator and to a specified observerand whose spectral reflectances or transmittances differ in thevisible wavelengths.3.2.1.1 DiscussionAs a conse
10、quence 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. (E 284)3.2.2 paramerism, nphenomenon in which specimenshaving different s
11、pectrophotometric curves produce approxi-mately the same color sensation under the same illuminatingand viewing conditions. (E 284)4. Significance and Use4.1 Metameric color matches result from the use of differentcolorants (pigments, dyes, and the like) in achieving the samecolor match. Usually, th
12、e purchaser requires that the colormatch be nonmetameric; this practice permits this requirementto be quickly tested in both field and laboratory. Wherenonmetameric matches are not possible or practicable, for costor other reasons, some limitation of metamerism may berequired. The procedures for est
13、imating the magnitude of1This practice is under the jurisdiction of ASTM Committee E12 on Color andAppearance and is the direct responsibility of Subcommittee E12.11 on VisualMethods.Current edition approved May 1, 2007. Published May 2007. Originallyapproved in 1982. Last previous edition approved
14、in 2003 as D 4086 92a (2003).2For 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.1Copyright ASTM International, 1
15、00 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.metamerism described in this practice provide methods forassessing the effectiveness of such limitation.5. Test Specimens5.1 This practice does not cover the preparation of testspecimens. The method shall be agreed up
16、on 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 light source, theobserver should view the specimens under one or more sourceshaving distinctly different spectral power d
17、istributions. Amongthe suggested sources are daylight, incandescent light, andfluorescent lamp light. The larger the differences in spectralcharacter of the sources, the easier it is to detect small degreesof metamerism.6.2 Observer MetamerismSpecimens that are a match toone observer under a given l
18、ight 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 among observers within the range ofnormal color vision. Replicate judgments by each observermay also be useful. Observer met
19、amerism is indicated whenthere is obvious disagreement among observers as to themagnitude and direction of the color difference.7. Procedures for Estimating Degrees of Metamerism7.1 When the existence of metamerism has been establishedby visual evaluation of a pair of specimens, as indicated inSecti
20、on 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, asspecified in Test Method D 2616, that display increasinglylarger color differences with each successive pair of grays inthe sc
21、ale. 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 two members of the test pair is compared to thelightness differences of the pairs on the gray scale, and the grayscale p
22、air 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 D 2616, that, thetotal color difference can be so evaluated in terms of anequivalent lightness difference. Observers can be expected torepro
23、duce 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 measured on aspectrophotometer that produces a reflectance curve in the visual region ofthe spectrum, direct comparison of such
24、 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 minimum of three times for specimens to be metameric. Specimens arenot metameric when the curves intersect only one or two tim
25、es in thevisible wavelengths, or when the curves do not intersect, but are merelyproportionally higher or lower in reflectance throughout the wavelengthregion. Judgment of the degree of metamerism by qualitative visualinspection of spectrophotometric curves requires considerable skill andexperience.
26、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 Section 7,8.1.5 Observed qualitative differences in hue, saturation,and lightness in accordance with the Procedure secti
27、on, seeEvaluation of the Color Difference, of Test Method D 2616,8.1.6 Number of observers and whether or not they weretested for color vision anomalies, and8.1.7 Description of light sources used as to type, size, colortemperature, and spectral power distribution.9. Precision and Bias9.1 PrecisionT
28、he only quantitative portion of this prac-tice, for which consideration of precision is appropriate, isSection 7, where use is made of Test Method D 2616. Theprecision statements of that test method should be consulted ifD 2616 is used.9.2 BiasThere are no recognized standards by which toassess the
29、bias of this practice.10. Keywords10.1 metamerism; visual examination-color; visualexamination-metamerismASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that
30、 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 time by the responsible technical committee and must be reviewed every five years andif not revised, either reapprov
31、ed 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 will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you fee
32、l 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 ASTM 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).D 4086 92a (2007)2
