1、Designation: E 2194 03Standard Practice forMultiangle Color Measurement of Metal Flake PigmentedMaterials1This standard is issued under the fixed designation E 2194; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last
2、revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.INTRODUCTIONSurfaces that exhibit different colors depending on the angles of illumination or sensing are said tobe “gonioapparent.” C
3、olorimetric values of reflecting gonioapparent materials are derived fromspectrophotometric (narrow band) or colorimetric (broad band) measurements of reflectance factor, atvarious angles of illuminating or sensing. When using spectral values, tristimulus values are computedusing the CIE Standard Ob
4、server and the spectrum of the illuminant, as described in Practice E 308.This practice, E 2194, specifies the measurement of color observed at various aspecular angles.1. Scope1.1 This practice covers the instrumental requirements,standardization procedures, material standards, and parametersneeded
5、 to make precise instrumental measurements of thecolors of gonioapparent materials. This practice is designed toencompass gonioapparent materials; such as, automotive coat-ings, paints, plastics, and inks.1.2 This practice addresses measurement of materials con-taining metal flake and pigments. The
6、optical characteristics ofmaterials containing pearlescent and interference materials arenot covered by this practice. The measurement of materialscontaining metal flakes requires three angles of measurementto characterize the colors of the specimen.NOTE 1Data taken by utilizing this practice are fo
7、r appearance qualitycontrol purposes. This procedure may not necessarily supply appropriatedata for pigment identification.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
8、-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:D 2244 Practice for Calculation of Color Differences fromInstrumentally Measured Color Coordinates2E 284 Terminology of Appearance2E 308 Practice for
9、Computing the Colors of Objects byUsing the CIE System2E 805 Practice for Identification of Instrumental Methods ofColor or Color-Difference Measurement of Materials2E 1164 Practice for Obtaining Spectrophotometric Data forObject Color Evaluation2E 1345 Practice for Reducing the Effect of Variabilit
10、y ofColor Measurement by Use of Multiple Measurements2E 1708 Practice for Electronic Interchange of Color andAppearance Data2E 1767 Practice for Specifying the Geometry of Observa-tions and Measurements to Characterize the Appearance ofMaterials22.2 CIE Document:3Publication No. 15.2 Colorimetry 2nd
11、 Edition2.3 NIST (NBS) Publication:4LC 1017 Standards for Checking the Calibration of Spec-trophotometers3. Terminology3.1 Terms and definitions in Terminology E 284 are appli-cable to this practice. See Section “Specialized Terminology onGonioapparent Phenomena.”3.2 DefinitionsUsually the term meta
12、llic refers to a metalmaterial. However, this standard employs the alternative defi-nition given in Terminology E 284 as:3.2.1 metallic, adjpertaining to the appearance of a go-nioapparent material containing metal flakes.1This practice is under the jurisdiction of ASTM Committee E12 on Color andApp
13、earance and is the direct responsibility of Subcommittee E12.12 on Metallic andPearlescent Colors.Current edition approved Feb. 10, 2003. Published May 2003.2Annual Book of ASTM Standards, Vol 06.01.3Available from The U.S. National Committee of the CIE (InternationalCommission on Illumination), C/o
14、 Thomas M. Lemons, TLA-Lighting Consultants,Inc., 7 Pond St., Salem, MA 01970.4Available from National Institute of Standards and Technology (NIST), 100Bureau Dr., Stop 3460, Gaithersburg, MD 20899-3460.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-29
15、59, United States.4. Summary of Practice4.1 This practice describes the procedures for the spectro-photometric and colorimetric measurement of metal flakepigmented materials. The results are reported in terms of CIEtristimulus values and other color coordinate systems. Stan-dardization of the instru
16、ment used to measure these materials isdefined. Guidelines are given for the selection of specimensand a measurement protocol given. Characterization of thesematerials requires measurement at a near-specular angle, a face(mid-aspecular angle) and a flop (far-specular) angle. Thesepreferred aspecular
17、 angles are 15, 45, and 110.5. Significance and Use5.1 Instrumental Measurement AnglesThis practice is de-signed to provide color data at specific measurement anglesthat can be utilized for quality control, color matching, andformulating in the characterization of metal flake pigmentedmaterials.5.2
18、MaterialsThis practice provides meaningful colorinformation for metal flake pigmented materials, but has notbeen evaluated for use with pearlescent materials or othergonioapparent materials. This practice has been tested andverified on paint and coatings, and the same principles shouldapply to plast
19、ics containing metallic flake.5.3 UtilizationThis practice is appropriate for measure-ment and characterization of metal flake pigmented materials.These data may be used for quality control, incoming inspec-tion, or color correction purposes.5.4 Specimen RequirementsEven though a pair of speci-mens
20、have the same color values at three angles, if there aredifferences in gloss, orange peel, texture, or flake orientation,they may not be a visual match.NOTE 2Information presented in this practice is based upon datataken on metallic materials coatings. Applicability of this practice to othermaterial
21、s should be confirmed by the user.6. Apparatus6.1 InstrumentThis practice requires measurement atmultiple angles of illumination and sensing, usually accom-plished by the use of a multiangle spectrophotometer asspecified in this practice to characterize metal flake pigmentedmaterials. Measurement wi
22、th a single geometry cannot char-acterize the gonioappearance of these materials.6.2 StandardizationA standardization plaque with as-signed spectral reflectance factor or tristimulus values traceableto a national standardizing laboratory for each specified as-pecular angle is required to standardize
23、 the instrument. Theinstrument manufacturer typically assigns the values to thisplaque.7. Geometric Conditions7.1 Conventional Color MeasurementIn general purposecolorimetry, the common geometry involves illuminating at45 and sensing at 0. This geometry is designated 45:0 (45/0).Reverse geometry has
24、 the illumination at 0 and the sensing at45. That is, the illuminator and sensing geometries areinterchanged. This reciprocal geometry is designated 0:45(0/45). Either geometry is used.7.1.1 A single bi-directional geometry is specified by illu-mination and sensing angles with respect to the normal
25、of theplane of the specimen. Angles are measured relative to thenormal. Angles on the same side of the normal as theillumination beam are written as positive angles; those on theother side are shown as negative, as shown in Fig. 1.7.2 Multiangle Uniplanar MeasurementThe color of me-tallic materials
26、specimens varies with the angle of view. Thusmeasurements must be taken at more than one angle tocharacterize the change of color with angle. The measurementgeometry for multiangle measurements is specified by aspecu-lar angles. The aspecular angle is the sensing angle measuredfrom the specular dire
27、ction, in the illuminator plane. The angleis considered positive when measured from the speculardirection towards the normal direction. Thus, if the specimen isilluminated at 45 to the normal the specular reflection will beat -45 (See Fig. 1). Sensing at 65 from the normal, and on thesame side of no
28、rmal as the illumination, is sensing 110 awayfrom the specular direction; that is an aspecular angle of 110.Thus, the aspecular angle is the sum of the materials colors, aspecific aspecular angle gives the same measurement regard-less of angle of illumination.57.3 Annular and Circumferential Geometr
29、yAnnular illu-mination provides incident light to a sample at all azimuthalangles. This type of illumination minimizes the contributionfrom directional effects such as the venetian blind effect andsurface irregularities. Circumferential illumination is an ap-proximation to annular illumination, inci
30、dent light being pro-vided from a discrete number of representative azimuthalangles. A large number or an odd number of illuminationsources more closely approximates annular illumination. An-nular or circumferential illumination minimizes directionaleffects. Therefore, measurements with annular or c
31、ircumferen-tial illumination may or may not correlate with how thatspecimen appears under directional illumination. For example,this system averaging may cause the measured color values of5Rodrigues, Die Farbe 37, pp. 65-78 (1990).NOTE 1Anormal illumination angle = 45 and anormal sensingangle = 65;
32、therefore, aspecular angle = 45 + 65 = 110.FIG. 1 Example of Illuminating and Sensing GeometryE2194032two specimens to be the same or similar, even though thesesame two specimens would not match visually due to the factthat one specimen exhibits the venetian blind effect.7.4 Recommended GeometryThe
33、instrument shall con-form to the following geometric requirements for measurementof reflectance factor unless otherwise agreed upon between thebuyer and the seller. The preferred aspecular angles formeasurement are 15, 45, and 110.NOTE 3Given a geometric configuration, the reverse geometry isconside
34、red equivalent, if all other components of the instrument design areequivalent; for example, in the example shown in Fig. 1, the same resultwould be obtained with the illumination angle at 65 and the sensing angleat 45. The aspecular angle would still be 110.NOTE 4Measurement angles below are stated
35、 in terms of aspecularangles. It has been established that for metallic materials colors, a specificaspecular angle gives the same measurement regardless of angle ofillumination. For pearlescent materials, it is known that color is also afunction of angle of illumination. The importance of this phen
36、omenon inmeasurement of pearlescent and interference materials for color differencefor quality control or color correction purposes has not been established.NOTE 5Uniplanar instruments can measure the venetian blind effect.Circumferential and annular illumination will not quantify this gonioap-paren
37、t effect.NOTE 6There are instruments commercially available with uniplanar,multiangle geometries that give results that characterize gonioapparentmaterials. These instruments will detect the venetian blind effect and otheranomalies. Table 1 delineates the preferred angles. Note that circumfer-ential
38、 geometry is limited to 10 when being observed.This observation usually occurs at approximately 45 cm (17.7 in.) fromthe eye. This specimen size is well suited for instrumental measurementand visual assessment.8.5.2 The surface of the specimen to be measured should beessentially planar.8.6 Specimen
39、Optical Requirements:8.6.1 UniformityReference specimens and test specimensshould be uniform in color and appearance when viewed in alighting booth. They must be similar in appearance to makemeaningful observations. There should be no appearance ofmottling or banding in the specimens.8.6.2 GlossSpec
40、imens should be uniform and similar ingloss when viewed in a lighting booth.8.6.3 Surface TextureThe standard and batch being com-pared should have substantially similar surface textures. Or-ange peel is a common example of surface texture.8.6.4 Specimen Flake DistributionExamine the speci-mens to e
41、nsure that they have similar flake size and distribu-tion. Dissimilar flake distributions will cause results to varysignificantly.8.6.5 OrientationConsistent orientation of the specimenfor presentation to the measuring instrument must be controlledfor repeatable measurements. This is necessary to mi
42、nimizeerrors due to indiscriminate matching of the directionality ofthe specimen to that of the instrument.9. Instrument Standardization9.1 Standardization is essential to ensure that spectrophoto-metric or tristimulus measurements with minimum bias arereported. For the measurement of reflectance fa
43、ctor, twostandardizations are required, namely,9.1.1 Optical Zero (0) Level StandardizationTo verify theoptical zero, the instrument manufacturer normally supplies ahighly polished black glass or a black trap that has an assignedreflectance factor value.9.1.2 Full Scale StandardizationTo standardize
44、 the instru-ment relative to the perfect reflecting diffuser, the instrumentmanufacturer should provide a standardization plaque withmultiangle calibration traceable to a standardizing laboratory.9.1.3 Photometric Scale ValidationTo ascertain properstandardization, measure a reference plaque immedia
45、tely afterthe standardization sequence and validate that the measuredvalues agree with the assigned values within 0.05 reflectanceunit.9.1.4 DiscussionTypically a neutral gray of 50 % reflec-tance is used for this purpose.10. Instrumental Performance Verification10.1 The use of validation standards
46、to verify spectropho-tometric performance of an instrument is recommended. TheseNOTE 1Example is for 15 aspecular angle.FIG. 3 Diagram of Ray Tracing Used to Calculate EffectiveAspecular Angles and their DistributionE2194034standards are readily available from multiple sources. Theinstrument user mu
47、st assume responsibility for obtaining thesestandards and their appropriate use. See NIST LC-1017 forfurther discussion.10.2 It is recommended that a user measure a durablegonioapparent specimen over time, recording and comparingvalues to ascertain proper instrument performance.11. Measurement Proce
48、dure11.1 Select Measurement VariablesSelect and validate theinstrumental configuration before measurement.11.1.1 Select the desired illuminating and sensing geom-etries. See Section 6 for definition of angles when measuringgonioapparent materials.11.1.2 Select the desired observer.11.1.3 Select the
49、desired illuminant.11.1.4 Select the desired colorimetric space, for example,CIELAB.11.2 Variation in measurements of gonioapparent materialsis largely due to inherent non-uniformity of these materials. Toobtain reproducible results, use large specimen areas that are490 mm2. These results can be achieved by a single measure-ment with a sampling aperture diameter 25 mm, or byaveraging multiple readings taken with a smaller aperture.Refer to Practice E 1345 for a description of averagingpractice.11.3 Measure the specimen(s) in accordance
