1、Designation: D4086 92a (Reapproved 2012)D4086 18Standard 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 revisi
2、on. A number 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 chara
3、cteristics 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 condit
4、ion to 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
5、conditions, and underanother set the direction and magnitude of the color difference may change.1. Scope1.1 This practice describes visual methods for detecting metamerism and for estimating the magnitude of a metameric colordifference.1.2 The practice is limited to the consideration of illuminant m
6、etamerism and observer metamerism. It is not designed to coverso-called geometric metamerism, in which members of specimen pairs change relative appearance as the angles of illuminationand viewing are changed, for example, because they incorporate flake metal or pearlescent colorants.This practice d
7、oes not covergonioapparent samples.1.3 This practice does not provide for the computation of indices of metamerism based upon instrumental measurement ofspectral characteristics.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the respo
8、nsibilityof the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine theapplicability of regulatory limitations prior to use.1.5 This international standard was developed in accordance with internationally recognized principles on stan
9、dardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D2616 Test Method for Evaluation of Visual Colo
10、r Difference With a Gray ScaleE284 Terminology of Appearance3. Terminology3.1 Definitions of appearance terms used in this practice may be found in Terminology E284.3.2 Definitions:3.2.1 metamerism, nproperty of two specimens that match under a specified illuminator and to a specified observer and w
11、hosespectral reflectances or transmittances differ in the visible wavelengths.1 This practice is under the jurisdiction of ASTM Committee E12 on Color and Appearance and is the direct responsibility of Subcommittee E12.11 on Visual Methods.Current edition approved July 1, 2012Oct. 1, 2018. Published
12、 August 2012October 2018. Originally approved in 1982. Last previous edition approved in 20072012 asD4086 92a (2007).(2012). DOI: 10.1520/D4086-92AR12.10.1520/D4086-18.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual
13、Book of ASTM Standardsvolume information, refer to the standardsstandards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may n
14、ot be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor
15、Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.2.1.1 DiscussionAs a consequence of the required difference, the two specimens may not match under a different illuminator or to a differentobserver. Similar considerations apply to two lights matching to a specified observer but
16、not to other observers. (E284)3.2.2 paramerism, nphenomenon in which specimens having different spectrophotometric curves produce approximately thesame color sensation under the same illuminating and viewing conditions. (E284)4. Significance and Use4.1 Metameric color matches result from the use of
17、different colorants (pigments, dyes, and the like) in achieving the same colormatch. Usually, the purchaser requires that the color match be nonmetameric; this practice permits this requirement to be quicklytested in both field and laboratory. Where nonmetameric matches are not possible or practicab
18、le, for cost or other reasons, somelimitation of metamerism may be required. The procedures for estimating the magnitude of metamerism described in this practiceprovide methods for assessing the effectiveness of such limitation.5. Test Specimens5.1 This practice does not cover the preparation of tes
19、t specimens. The sample preparation method shall be agreed upon betweenthe purchaser and the seller.6. Procedure for Visual Detection of Metamerism6.1 Illuminant MetamerismAfter observing that a pair of specimens is a visual match under one light source, the observershould view the specimens under o
20、ne or more sources having distinctly different spectral power distributions.Among the suggestedsources are daylight, incandescent light, and fluorescent lamp light. fluorescent lamp light, and LED light or other solid-statesources, preferable of very different color temperatures in the range of 2700
21、 to 7500 K. The larger the differences in spectralcharacter of the sources, the easier it is to detect small degrees of metamerism.Although two sources are required for determinationor metamerism, it is recommended that one use three sources. Two of the sources should have a very different color tem
22、perature;such as the difference in correlated color temperature between daylight and incandescent. The remaining source should representthe source of illumination expected to be used by the end user. It is recommended that observations be made in a controlledenvironment; such as a lighting booth or
23、under a luminaire.6.2 Observer MetamerismSpecimens that are a match to one observer under a given light source are then viewed by othernormal observers under the same conditions. The use of a light booth is recommended, but not required. Typically, five to tenobservers should be used so that the res
24、ults are not biased by differences among observers within the range of normal color vision.Replicate judgments by each observer may also be useful. Observer metamerism is indicated when there is obvious disagreementamong observers as to the magnitude and direction of the color difference.7. Procedur
25、es for Estimating Degrees of Metamerism7.1 When the existence of metamerism has been established by visual evaluation of a pair of specimens, as indicated in Section6, the degree of metamerism for that combination of source and observer can be determined by a visual estimate of the colordifference.
26、difference observed under the source where the difference was manifested. Use is made of paired gray scales, asspecified in Test Method D2616, that display increasingly larger color differences with each successive pair of grays in the scale.The metameric specimen pair is placed in juxtaposition wit
27、h the edge of the gray scale and compared with various gray pairs. Thetotal perceived color difference between the two members of the test pair is compared to the lightness differences of the pairs onthe gray scale, and the gray scale pair is selected that is the best visual equivalent to the color
28、difference of the test pair. pairfollowing the procedures given in Test Method D2616. It is assumed, as in the Significance and Use section in Test Method D2616,that, the total color difference can be so evaluated in terms of an equivalent lightness difference. Observers can be expected toreproduce
29、such evaluations within a half-step on the gray scale.NOTE 1Visual Evaluation of Spectral Reflectance CurvesWhen specimens that match under one set of circumstances are measured on aspectrophotometer that produces a reflectance curve in the visual region of the spectrum, direct comparison of such cu
30、rves will disclose if there ismetamerism. It is convenient to plot the spectral curves of the two members of a metameric pair on the same sheet. The curves must intersect a minimumof three times for specimens to be metameric. Specimens are not metameric when the curves intersect only one or two time
31、s in the visible wavelengths,or when the curves do not intersect, but are merely proportionally higher or lower in reflectance throughout the wavelength region. Judgment of the degreeof metamerism by qualitative visual inspection of spectrophotometric curves requires considerable skill and experienc
32、e.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,D4086 1828.1.5 Observed qualitative differences in hue, saturation, and lightness in accordance with the Pro
33、cedure section, see Evaluationof the Color Difference, of Test Method D2616,8.1.6 Number of observers and whether or not they were tested for color vision anomalies, and8.1.7 Description of light sources used as to type, size, color temperature, and spectral power distribution.9. Precision and Bias9
34、.1 PrecisionThe only quantitative portion of this practice, for which consideration of precision is appropriate, is Section 7,where use is made of Test Method D2616. The precision statements of that test method should be consulted if D2616 is used.9.2 BiasThere are no recognized standards by which t
35、o assess the bias of this practice.10. Keywords10.1 metamerism; visual examination-color; visual examination-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 expressl
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