1、Designation:D261696(Reapproved2003) Designation: D2616 12Standard Test Method forEvaluation of Visual Color Difference With a Gray Scale1This standard is issued under the fixed designation D2616; the number immediately following the designation indicates the year oforiginal adoption or, in the case
2、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.INTRODUCTIONThis test method was developed to provide a precise procedure for visually evaluating colordi
3、fference of non-self luminous specimens. It was patterned after a method standardized by theAmerican Association of Textile Chemists and Colorists (AATCC)2designed to evaluate “change incolor” and this antecedent was reflected in the original title.This test method provides for evaluation of small t
4、o moderate color differences (less than 15CIELAB (International Commission on Illumination) color difference units) by comparing testspecimens to a series of paired gray color chips having progressively larger lightness differences.Color difference is rated according to which of nine gray pairs of d
5、ifferences is visually closest to thetest pair, or by interpolation between gray-pair differences.The gray-scale pairs are specified in terms of decimal differences in CIELAB color space. Thischange together with two continuous, decimal numerical scale equations modeling the original scalecomprise t
6、he major differences between the previous edition and this revision. The changes were madeto provide an ASTM test method that parallels closely the AATCC method.1. Scope1.1 This test method describes a painted gray scale and the procedure to be used in the visual evaluation of color differencesof no
7、n-self luminous materials by comparison to this scale.1.2 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability o
8、f regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:3E284 Terminology of AppearanceDE1729Practice for Visual Appraisal of Colors and Color Differences of Diffusely-Illuminated Opaque Materials Practice forField Collection of Dried Paint Samples for Subsequent Lead Determin
9、ationE1499 Guide for Selection, Evaluation, and Training of Observers2.2 AATCC Procedures:AATCC Evaluation Procedure 1,Gray1 Gray Scale for Color Change23. Terminology3.1 Definitions:3.1.1 Definitions of appearance terms in Terminology E284 are applicable to this test method.4. Summary of Test Metho
10、d4.1 The gray scale consists of nine pairs of neutral gray color standards of which Reference Pair 5 is two examples of the same1This test method is under the jurisdiction ofASTM Committee E12 on Color andAppearance and is the direct responsibility of Subcommittee E12.11 on Visual Methods.Current ed
11、ition approved Dec. 1, 2003. Published December 2003. Originally approved in 1967. Last previous edition approved in 1996 as D261696. DOI:10.1520/D2616-96R03.Current edition approved July 1, 2012. Published September 2012. Originally approved in 1967. Last previous edition approved in 2003 as D2616
12、96 (2003) which waswithdrawn April 2012 and reinstated in July 2012. DOI: 10.1520/D261612.2Technical Manual of the American Association of Textile Chemists and Colorists, P.O. Box 12215, Research Triangle Park, NC 27709, Vol 68, 1993,86, 2011, pp.348349.365366.3For referencedASTM standards, visit th
13、eASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.1This document is not an ASTM standard and is intended only to provide the user of an ASTM standard a
14、n indication of what changes have been made to the previous version. Becauseit may not 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 t
15、o be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.gray. One element common to each pair is the gray of Reference Pair 5; the other element, being progressively lighter, providesa succession of light
16、ness differences. Total color differences between non-self luminous specimens are expressed as eitherfractional, linear scale value between 1 and 5 or as equivalent CIELAB color differences (DE*ab) by comparison with the paireddifferences of the gray scale, which are predominantly lightness differen
17、ces.NOTE 1The gray specimen common to each pair is specified to have CIE 1976 metric lightness, L*=41.2(+0.6,0.0). * = 41.2 (+ 0.6, 0.60).5. Significance and Use5.1 The total perceived color difference between two non-self luminous specimens is compared as an equivalent lightnessdifference between t
18、wo neutral gray specimens on a gray scale. A fundamental assumption is made that the total color differencecan be so evaluated in terms of an equivalent lightness difference. Only the total color differences, that is, a summation of thedifferences in hue, lightness, and chroma between two specimens
19、is evaluated; this test method is not applicable to the separateprecise evaluation of the hue, lightness, and chroma components of color difference.5.2 The total color difference determined by this test method depends on the degree of uniformity of the specimens and on thesharpness of the dividing l
20、ine between them. The color difference between specimens having rough or mottled surfaces appearssmaller than it would if the specimens had smooth and uniform surfaces. Thus the equivalent CIELAB lightness differencedetermined for non-uniform specimens will be smaller than for uniform specimens. Lik
21、ewise, specimens whose dividing line isnot sharp will appear to have smaller color differences than those with sharp dividing lines, and for this reason, the equivalentvisually observed CIELAB lightness differences will be smaller than the color differences obtained from instrumentalmeasurements.5.2
22、.1 Aphysically sharp border between colors differing slightly in the yellow-blue direction in color space appears diffuse. Theperceived color difference is noticeably increased by a hairline black separation. This technique imposes a more rigorous test ofsuch small differences.5.3 In the CIELAB syst
23、em, a unit of color difference is intended to represent the same visual difference in each of the threeattributes; lightness, hue and chroma or alternatively lightness, redness-greeness, yellowness-blueness. It is valid to express colordifferences that are not simply lightness differences by compari
24、son to a lightness-difference scale.5.4 Personnel to be employed in the evaluation of color differences with the paired gray scale should be tested for color visionusing the procedures in Guide E1499.6. Apparatus6.1 Gray Scale Chart,4having the characteristics as shown in Table 1. . The DE* values i
25、n this table are only for the purposeof determining if the Gray Scale Chart itself meets performance specifications. It is not to be used to convert either visual ratingsto DE* values or DE* values to Gray Scale ratings.NOTE 2It should be recognized that the practical requirements of gray scale prod
26、uction mitigate against members of a reference pair either beingabsolutely neutral, or being of identical near-neutral chromaticity. However, chromaticity differences, if present, are of negligible magnitude.6.2 Gray MasksLight gray masks with rectangular openings shall be used to ensure comparison
27、of equal areas of specimenand reference pairs. Masks are included with each AATCC gray-scale chart.6.3 Color Matching Light BoothSee Practice D1729 E1729 for a description of an appropriate color-matching light booth foruse in visual evaluation of color differences.7. Preparation of Specimens7.1 Spe
28、cimens shall be uniform in color and gloss and shall be free of scratches and other imperfections of surface texture. Thespecimen being compared to the standard should have the same gloss and surface texture as the standard for maximum precisionof color differences determination.4Available from Amer
29、ican Association of Textile Chemists and Colorists (as Gray Scale for Color Change).TABLE 1 Gray Scale CharacteristicsAATCC StepDesignationsCIELAB (DE*)Color Difference Tolerance(6)5.0 0.0 0.24.5 0.8 0.24.0 1.7 0.33.5 2.5 0.33.0 3.4 0.42.5 4.8 0.52.0 6.8 0.61.5 9.6 0.71.0 13.6 1.0D2616 1228. Procedu
30、re8.1 Illumination and Viewing:8.1.1 Place the specimens and the paired gray-scale charts in the same plane on a horizontal surface with a neutral background(middle gray to white) under the prescribed light source. The light source shall be daylight or a daylight simulator, for examplea color-matchi
31、ng light booth. Make sure that the specimen pairs whose color differences are to be evaluated are juxtaposed as arethe reference pairs, so that there is no space between the elements of a pair. It is also desirable to locate the specimen pairsimmediately adjacent to the reference pairs when making a
32、 judgment. These procedures are designed to provide ease of handlingand optimum accuracy in judging color differences.8.1.2 Avoid specular reflection of the source by illuminating the specimens at an angle of about 45 and viewing themperpendicularly, or the reverse geometry. Shield specimens from ex
33、traneous light sources and resulting reflected images by placinga black cloth at the mirror reflection position.8.1.3 Cover the specimens with the gray mask so that equivalent areas are from each member of the specimen pair.8.2 Evaluation of the Color Difference:8.2.1 If the color difference of the
34、specimen pair is equal to that of any of the reference pairs, record it in terms of the scalevalue. If the difference appears to be between those of two adjacent reference pairs, record it by interpolation between the scalevalues of the two pairs.8.2.2The gray scale value can be converted to a calcu
35、lated CIELAB color difference and likewise, a CIELAB color differencecan be converted to a gray scale value. If the gray scale value (GS) is three or greater then the following equation describes therelationship between gray scale value and CIELAB DE*:DE*51.752GS!;D2616-96R03_1 (1)else if the gray s
36、cale value (GS) is less than three the following equation can be used:DE*50.8510Alog2!52GS!.D2616-96R03_2 (2)8.3 Character of Color Difference:8.3.1 It is desirable to record the direction of the color difference of the specimens in general terms by indicating the directionof difference in hue (as b
37、luer, greener, etc.), or the difference in chroma (as grayer or more vivid), or the difference in lightness(as lighter or darker). It is essential to indicate whether such descriptive differences apply to the specimen as compared to thestandard, or apply to the standard as compared to the specimen.9
38、. Report9.1 When a report is required, the following information should be included:9.1.1 Designation of the specimens,9.1.2 Gray scale rating in accordance with 8.2.1,9.1.2.1CIELAB color difference estimated from the gray scale rating in accordance with 8.2.2,9.1.3 Observed qualitative differences
39、in hue, saturation, and lightness in accordance with 8.3.1,9.1.4 Viewing conditions including light source, surround, and geometric aspects of viewing (reference to Practice D1729E1729 when applicable),9.1.5 Description of gloss or surface characteristics, or both, and9.1.6 Identity of observers by
40、name or code designation.10. Precision and Bias10.1 PrecisionIt is impossible to state in absolute terms the generalized precision of this test method for all observers, for allcolor differences in all parts of color space, and for all conditions of lighting and surround. The stated repeatability an
41、dreproducibility of this test method assume observers of normal color vision, daylight quality illumination of at least 1000 lux (100foot-candles), use of the specified surround and angles of illumination and viewing, equivalent gloss, and texture of pairs underexamination.10.2 When the above condit
42、ions are fulfilled, the following statements of repeatability and reproducibility will apply:10.2.1 RepeatabilityRepeat ratings of the same specimen pair by one observer in one laboratory should give results agreeingto within one-half-the difference between the two closest reference pairs.10.2.2 Rep
43、roducibilityRepeat ratings of the same specimen pair by different observers in different laboratories or by usingdifferent sets of reference gray scales should give results agreeing to within the difference between the two closest reference pairs.11. Keywords11.1 AATCC; color difference; gray scaleD
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