ASTM_D_4086_-_92a_2012.pdf

Designation:D408692a(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 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 characteristics 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 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 conditions,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 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 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 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 ScaleE284 Terminology of Appearance3.Terminology3.1 Definitions of 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 DiscussionAs a consequence of the requireddifference,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 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.Usually,the 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 estimating 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 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 serviceastm.org.For Annual Book of ASTMStandards volume information,refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 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 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 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 it is to detect small degreesof metamerism.6.2 Observer MetamerismSpecimens tha