1、Designation: E313 10E313 15Standard Practice forCalculating Yellowness and Whiteness Indices fromInstrumentally Measured Color Coordinates1This standard is issued under the fixed designation E313; 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.1. Scope1.1 This practice provides numbers that correlate with visual ratings of yellowness or whiteness
3、 of white and near-white orcolorless object-color specimens, viewed in daylight by an observer with normal color vision. White textiles, paints, and plasticsare a few of the materials that can be described by the indices of yellowness or whiteness calculated by this practice.1.2 For a complete analy
4、sis of object colors, by a specified observer and under a specified illuminant, use of three parametersis required. For near-white specimens, however, it is often useful to calculate single-number scales of yellowness or whiteness.Thispractice provides recommended equations for such scales and discu
5、sses their derivations and uses, and limits to their applicability(see also Ref (1)2).1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.4 This standard does not purport to address all of the safety concerns, if any, associ
6、ated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:3D1535 Practice for Specifying Color by the Munsell SystemD1729
7、 Practice for Visual Appraisal of Colors and Color Differences of Diffusely-Illuminated Opaque MaterialsD1925 Test Method for Yellowness Index of Plastics (Withdrawn 1995),4E284 Terminology of AppearanceE308 Practice for Computing the Colors of Objects by Using the CIE SystemE805 Practice for Identi
8、fication of Instrumental Methods of Color or Color-Difference Measurement of MaterialsE991 Practice for Color Measurement of Fluorescent Specimens Using the One-Monochromator MethodE1164 Practice for Obtaining Spectrometric Data for Object-Color EvaluationE1247 Practice for Detecting Fluorescence in
9、 Object-Color Specimens by SpectrophotometryE1331 Test Method for Reflectance Factor and Color by Spectrophotometry Using Hemispherical GeometryE1345 Practice for Reducing the Effect of Variability of Color Measurement by Use of Multiple MeasurementsE1347 Test Method for Color and Color-Difference M
10、easurement by Tristimulus ColorimetryE1348 Test Method for Transmittance and Color by Spectrophotometry Using Hemispherical GeometryE1349 Test Method for Reflectance Factor and Color by Spectrophotometry Using Bidirectional (45:0 or 0:45) GeometryE1360 Practice for Specifying Color by Using the Opti
11、cal Society of America Uniform Color Scales SystemE1499 Guide for Selection, Evaluation, and Training of ObserversE1541 Practice for Specifying and Matching Color Using the Colorcurve System (Withdrawn 2007)51 This practice is under the jurisdiction of ASTM Committee E12 on Color and Appearance and
12、is the direct responsibility of Subcommittee E12.04 on Color andAppearance Analysis.Current edition approved July 1, 2010Jan. 1, 2015. Published July 2010February 2015. Originally approved in 1967. Last previous edition approved in 20052010 asE313 05.E313 10. DOI: 10.1520/E0313-10.10.1520/E0313-15.2
13、 The boldface numbers in parentheses refer to the list of references at the end of this practice.3 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standardsstandar
14、ds Document Summary page on the ASTM website.4 The last approved version of this historical standard is referenced on www.astm.org. Replaced by Section 6 of E313.5 The last approved version of this historical standard is referenced on www.astm.org.This document is not an ASTM standard and is intende
15、d only to provide the user of an ASTM standard an 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
16、versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13. Terminology3.1 Terms and definitions in Terminology E284 are applicable to this practice.3.2 Defi
17、nitions:3.2.1 perfect reflecting diffuser, nideal reflecting surface that neither absorbs nor transmits light, but reflects diffusely, with theradiance of the reflecting surface being the same for all reflecting angles, regardless of the angular distribution of the incident light.3.2.2 whiteness, nt
18、he attribute of color perception by which an object color is judged to approach the preferred white.3.2.3 whiteness index, WI, na number, computed by a given procedure from colorimetric data, that indicates the degree ofdeparture of an object color from that of a preferred white.3.2.4 yellowness, nt
19、he attribute of color perception by which an object color is judged to depart from colorless or a preferredwhite toward yellow.3.2.5 yellowness index, YI, na number, computed by a given procedure from colorimetric or spectrophotometric data, thatindicates the degree of departure of an object color f
20、rom colorless or from a preferred white, toward yellow.3.2.5.1 DiscussionNegative values of YI denote departure toward blue.3.3 Definitions of Terms Specific to This Standard:3.3.1 near white, na color having a Munsell value greater than 8.3 (luminous reflectance factor Y = 63) and Munsell chromano
21、greater than 0.5 for B hues, 0.8 for Y hues, and 0.3 for all other hues.3.3.2 preferred white, ncolor of a white standard used as the basis for calculating indices of whiteness or yellowness as thedeparture of the color of the specimen from that of the preferred white; in this practice, the perfect
22、reflecting diffuser.4. Summary of Practice4.1 The calculations described in this practice assume that specimens have been measured according to Practices E1164 andE308 and one of the Test Methods E1331, E1347, E1348, or E1349, depending on the type of specimen and measuring instrumentused (see also
23、Practice E805).4.2 This practice takes as a starting point for the calculations CIE tristimulus values X, Y, and Z for one of the CIE standardobservers and one of the CIE standard or recommended illuminants of daylight quality. Such tristimulus values are available byuse of modern color measuring in
24、struments.4.3 Equations for the preferred methods of calculating YI and WI are described in Sections 6 and 7, respectively. Equations forcalculating other quantities used as indices of yellowness or whiteness are given in Appendix X1 and Appendix X2, respectively.5. Significance and Use5.1 This prac
25、tice should be used only to compare specimens of the same material and same general appearance. For example,a series of specimens to be compared should have generally similar gloss, texture, and (if not opaque) thickness, and translucency.5.2 For yellowness measurement, this practice is limited to s
26、pecimens having dominant wavelength in the range 570 to 580 nm,or Munsell hue approximately 2.5GY to 2.5Y. For whiteness measurement, this practice is limited to specimens having Munsellvalue greater than 8.3 (CIE Y greater than 65) and Munsell chroma no greater than 0.5 for B hues, 0.8 for Y hues,
27、and 0.3 for allother hues (see 3.3.1).5.3 The combination of measurement and calculation leading to indices of yellowness or whiteness is a psychophysical process,that is, the procedures specified are designed to provide numbers correlating with visual estimates made under specified typicalobserving
28、 conditions. Because visual observing conditions can vary widely, users should compare calculated indices with visualestimates to ensure applicability. Some standards addressing the visual estimation of color and color difference are PracticesD1535, D1729, E1360, and E1541, and Guide E1499.5.4 This
29、practice does not cover the preparation of specimens, a procedure that may affect significantly the quantities measured.In general, specimens should be prepared and presented for measurement in the manner that is standard for the test beingperformed. Select enough specimens or specimen areas to prov
30、ide an average result that is representative of each sample to betested. See Practice E1345.6. Yellowness Index6.1 This section contains two main parts: 6.2 Historical background and 6.3 Calculation of currently recommended YellownessIndex. If the user wants to calculate the currently recommended Ye
31、llowness Index (YI), it is recommended to skip directly to 6.3.6.2 BackgroundThe currently recommended equation for the calculation of yellowness index is derived from an equation dueto Hunter (2) in 1942: YI = (A B)/G, where A, B, and G are, respectively, amber or red, blue, and green colorimeter r
32、eadings.E313 152Another version, used in the 1940s to 1960s for transparent plastics (3, 4), was based on transmittances near the ends of the visiblewavelength region: YI = 100(T680 T420)/T560 (with a factor of 100 introduced to give values of YI near unity). This equation failedto account correctly
33、 for differences in the spectral transmittance curves of such plastics, especially after the adoption of ultravioletlight absorbers to improve weathering, and was soon abandoned. When, in 1957, ASTM solicited new equations for calculatingyellowness indices, HuntersHunters equation was converted (5)
34、into CIE tristimulus value form by using HuntersHuntersapproximate relations between colorimeter readings and those tristimulus values; the resulting equation, YI = 100(1.28X 1.06Z)/Y, was adopted for use in Test Method D1925 in 1962.6.2.1 In the original form of Test Method E313, an alternative equ
35、ation was recommended for a yellowness index. In terms ofcolorimeter readings, it was YI = 100(1 B/G). Its derivation assumed that, because of the limitation of the concept to yellow (orblue) colors, it was not necessary to take account of variations in the amber or red colorimeter reading A. This e
36、quation is no longerrecommended.6.2.2 Significant Digits and PrecisionThe coefficients of Test Method D1925 equation were rounded to the number of digitsshown, commensurate with the precision of then-existing color measurement instrumentation. It was not intended that moresignificance should be attr
37、ibuted to values of YI than that implicit in this number of digits. As instrumentation was improved,however, it was found that some instruments unexpectedly gave nonzero values of YI for clear air or the perfect reflecting diffuser.One suggested (1), p. 205) remedy for this presumed failure of the e
38、quation was to increase the number of digits in the numericalcoefficients from two to ten after the decimal point, despite the obvious lack of significance of most of these digits. With moderninstrumentation, it is believed that two digits added to the coefficients in the original Test Method D1925
39、equation suffice to bringthe nonzero value of YI below 0.0005 on average. The new coefficients are given to this precision in 6.2.3.6.2.3 Derivation of EquationsSeveral sets of coefficients are involved in the derivation of the final equations recommendedfor calculating yellowness indices. With them
40、 evaluated, it is possible to derive highly precise equations for both the CIE 1931standard observer and the 1964 supplementary standard observer, in combination with either CIE standard illuminant C or D65.The results are given in Table 1.6.2.3.1 The first set of coefficients required, consists of
41、the tristimulus values Xn,Yn, and Zn of the perfect reflecting diffuser (orclear air) for the above observer-illuminant combinations. These are established by the CIE, and for the present derivation weretaken from the tables of tristimulus weighting factors in Practice E308.6.2.3.2 From these “white
42、 point” values, it is possible to calculate the coefficients in Hunters equation relating tristimulus valueX and colorimeter readings A and B: X = Xn(FAA + FBB), thus improving on the approximation FA = 0.8 and FB = 0.2 originallyused.6.2.3.3 The coefficients in revised Test Method D1925 equations f
43、or YI can be calculated, rounded, and adjusted in the lastretained significant digit to minimize the residual error in the white point values. These coefficients are given in Table 1 as CX andCZ. The tabulation of the residual white point error completes the table.6.2 Significant Digits and Precisio
44、nThe coefficients of Test Method D1925 equation were rounded to the number of digitsshown, commensurate with the precision of then-existing color measurement instrumentation. It was not intended that moresignificance should be attributed to values of YI than that implicit in this number of digits. A
45、s instrumentation was improved,however, it was found that some instruments unexpectedly gave nonzero values of YI for clear air or the perfect reflecting diffuser.One suggested (1), p. 205) remedy for this presumed failure of the equation was to increase the number of digits in the numericalcoeffici
46、ents from two to ten after the decimal point, despite the obvious lack of significance of most of these digits. With moderninstrumentation, it is believed that two digits added to the coefficients in the original Test Method D1925 equation suffice to bringthe nonzero value of YI below 0.0005 on aver
47、age. The new coefficients are given to this precision in 6.3.6.3 Derivation of EquationsCalculation of Yellowness Index (YI)SeveralYI sets of coefficients are involved in the derivationof the final equations recommended for calculating yellowness indices. With them evaluated, it is possible to deriv
48、e highly preciseequations for both can be calculated for either illuminant C or D65, and either the CIE 1931 standard observer and the 1964supplementary standard observer, in combination with either CIE standard illuminant colorimetric observer (2), Cor Dthe65. Theresults are given in CIE 1964 stand
49、ard colorimetric observer Table 1.(10).TABLE 1 Coefficients of the Equations for YellownessIndexQuantities Used in the Earlier Forms of Yellowness IndexEquationsQuantity CIE Standard Illuminant and Standard ObserverC, 1931 D65, 1931 C, 1964 D65, 1964Xn 98.074 95.047 97.285 94.811Yn 100.000 100.000 100.000 100.000Zn 118.232 108.883 116.145 107.304FA 0.7987 0.8105 0.7987 0.8103FB 0.2013 0.1895 0.2013 0.1897CX 1.2769 1.2985 1.2871 1.3013CZ 1.0592 1.1335 1.0781 1.1498Residual error 0.0006 0.0004 0.0004 0.0006E313 1536.3.1 The first set of coe
