ANSI T 1215 SP-2012 The determination of instrumental color differences.pdf

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1、T 1215 sp-12 FORMERLY TIP 0804-01 STANDARD PRACTICE 1998 REVISED 2003 REVISED 2007 REVISED 2012 2012 TAPPI The information and data contained in this document were prepared by a technical committee of the Association. The committee and the Association assume no liability or responsibility in connect

2、ion with the use of such information or data, including but not limited to any liability under patent, copyright, or trade secret laws. The user is responsible for determining that this document is the most recent edition published. Approved by the Standard Specific Interest Group for this Test Meth

3、od TAPPI CAUTION: This Test Method may include safety precautions which are believed to be appropriate at the time of publication of the method. The intent of these is to alert the user of the method to safety issues related to such use. The user is responsible for determining that the safety precau

4、tions are complete and are appropriate to their use of the method, and for ensuring that suitable safety practices have not changed since publication of the method. This method may require the use, disposal, or both, of chemicals which may present serious health hazards to humans. Procedures for the

5、 handling of such substances are set forth on Material Safety Data Sheets which must be developed by all manufacturers and importers of potentially hazardous chemicals and maintained by all distributors of potentially hazardous chemicals. Prior to the use of this method, the user must determine whet

6、her any of the chemicals to be used or disposed of are potentially hazardous and, if so, must follow strictly the procedures specified by both the manufacturer, as well as local, state, and federal authorities for safe use and disposal of these chemicals. The determination of instrumental color diff

7、erences 1. Scope This standard practice provides a general introduction to the use of color differences and a list of the most widely used equations to obtain them. Color differences can be used 1) as a guide to establishing color tolerances in the production of pulp, paper, and paperboard, 2) for t

8、he determination of buying and selling tolerances of color, 3) to provide a method of determining the adequacy of color matches. 2. Significance Although the eye is unsurpassed as a detector of a difference in color between two samples, it is, however, very poor in assessing the size and nature of t

9、hat difference. Two common examples will attest to this statement: The redder yellow of a pair of yellows will generally be assessed as the stronger one; the brighter of a pair of colors will generally be assessed as weaker. This is no fault of the individual, but rather a defect of the visual proce

10、ss, for human vision is not designed to distinguish between the various attributes of color (hue, saturation and lightness) but rather to give an assessment based on an integration of all three. In addition, many other factors influence the visual process: health, lighting, age, etc. 3. Safety preca

11、utions There are no specific safety precautions associated with this standard practice. 4. Development 4.1 Around 1930 several developments laid the foundation for most of the important developments we have had in color instrumentation to date. Ostwald, Munsell, the CIE, and Adams all described colo

12、r spaces which would help to attach a number designation to a color. Further, the Ostwald, Munsell, and Adams systems attempted to space the T 1215 sp-12 The determination of instrumental color differences / 2 colors equally in all directions. The CIE set up the specifications for the Tristimulus Va

13、lues X, Y and Z in 1931. All data were laboriously hand calculated which was far from a simple routine. 4.2 Several others collaborated during the 1930s and 1940s to develop colorimeters to measure tristimulus values or some modification of them directly. These led to the widely used filter colorime

14、ters. 4.3 Many papers were published which were aimed at giving a more uniform color space in the 1940s. The color difference formulae of McAdam, Adams, Saunderson-Milner, etc. were developed, but the calculations were still too long to be done practically on a production level. In the 1950s came th

15、e computational aids: nomographs, tables, charts, and even slide rules. Nickerson (1) and Buc (2) published tables of data to assist in the computation of the Adams color difference equation. Davidson L, a, b; or R, G, B. These data are directly substituted in the appropriate color difference equati

16、on and the color difference calculated. Manufacturers of the colorimeters may give the conversion formulae needed to convert from one set of reading to another, so that color differences can be computed in other color systems. Some colorimeters have been internally programmed to read out color diffe

17、rences directly. Some instruments can provide color differences in more than one system, illuminant, and standard observer. 5.2 Spectrophotometers provide percent reflectance data at discreet intervals throughout the visible spectrum. The spectral range is commonly 400 to 700 nanometers (nm) at 10 o

18、r 20 nanometer intervals. The range may be expanded to include 380 to 740 nm, and the interval may be only 5 nm. These data must be converted to tristimulus values (10, 11, 12) before color differences can be calculated. A programmed digital computer is required for this operation. The tristimulus d

19、ata are then used to compute the color difference between specimens as was described for colorimeters. 6. Official recommendations 6.1 No one color difference formula has been shown to be superior so as to receive the official endorsement of a major standardization body. The CIE (12, 13,) recommende

20、d the study of four (1964 CIE, Cube-Root, Munsell 3 / The determination of instrumental color differences T 1215 sp-12 Renotation, and the FMC II) with a view toward adoption as an international standard. The Helmholtz Memorial Symposium on Color Metrics reported the disappointing results of seven y

21、ears of the study (14). Two new equations were set forth for the possible adoption (CIE L*U*V*. and CIE L*a*b*) in 1976 (16). Additional terms were defined for hue and saturation. 6.2 The Textile Committee of the International Standards Organization (16) suggested the Adams-Nickerson equation be use

22、d until a better one is found. They recommended that the factor of 40, as recommended by Nickerson (1), be used and the color difference unit be designated AN-40. This unit is commonly, but erroneously, referred to as the NBS unit. The American Association of Textile Chemists 1 Y 100 u* = 13 L*(u -

23、u0) v* = 13 L*(v - v0) T 1215 sp-12 The determination of instrumental color differences / 4 with: 00000000031593154ZYXYVZYXXu3Z+ 15Y + X9Y= v 3Z + 15Y + X4X= u+=+=X0, Y0, Z0define the color of the nominally white object-color stimulus, with Y0= 100 8.3 CIE 1976 (L*a*b*), CIELAB (21), Pauli (22) E =

24、(L*)2+ (a*)2+ (b*)21/2where: L* = 116(Y/Yn)1/3- 16 a* = 500(X/Xn)1/3- (Y/Yn)1/3 b* = 200(Y/Yn)1/3- (Z/Zn)1/3X/Xn, Y/Yn, Z/Zn 0.01 The tristimulus values Xn, Yn, Zndefine the color of the nominally white object-color stimulus. Usually, the white object-color stimulus is given by the spectral radiant

25、power of one of the CIE standard illuminants reflected into the observers eye by the perfect reflecting diffuser. Under these conditions, Xn, Yn, Znare the tristimulus values of the standard illuminant with Ynequal to 100. The total difference E*abbetween two colors each given in terms of L*, a*, b*

26、 is calculated from: E*ab= (L*)2 + (a*)2+ (b*)21/2In calculating L*, values of Y/Ynless than 0.01 may be included if the normal formula is used for values of Y/Yngreater than 0.008856, and the following modified formula is used for values of Y/Ynequal to or less than 0.008856: L* = 903.3(Y/Yn) Y/Yn

27、0.008856 In calculating a* and b*, values of X/Xn, Y/Yn, Z/Znless than 0.01 may be included if the normal formula are replaced by the following modified formulae: a* = 500(X/Xn) - (Y/Yn) b* - 200 (Y/Yn) - (Z/Zn) where: (X/Xn) = (X/Xn)1/3X/Xn 0.008856 (X/Xn) = 7.787(X/Xn) + 16/116 X/Xn0.008856 (Y/Yn)

28、 = 7.787(Y/Yn) + 16/116 Y/Yn0.008856 (Z/Zn) = 7.787(Z/Zn) + 16/116 Z/Zn 0.008856 X0, Y0, Z0are as defined in CIE 1976 (L*u*v*) 5 / The determination of instrumental color differences T 1215 sp-12 This space and formula are simplified versions of the Adams-Nickerson version. It is intended to give a

29、more easily computed space and equation. They are widely used for colorant formulation, color tolerances, and quality control determinations. 8.4 A CMC color difference formula was developed by the Color Measurement Committee of the Society of Dyers and Colorists (18, 23, 24). The CMC formula evolve

30、s from the CIELAB system, previously described. An improvement is claimed in agreement between calculated color difference values and visual assessment of color difference. The coordinates lightness (L*), chroma (C*), and hue angle (h) are derived from CIE L*, a* and b* values: C* = a*2+ b*21/2h = a

31、rctan (b*/a*) Color difference calculated in terms of L*, C* and h is: E* = L*2+ C*2+ H*21/2where for small color differences H*=C*h (/180) The CMC (:c) formula is then: E CMC (:c) = L*/SL)2+ (C*/cSc)2+ (H*/SH)21/2where: SL= 0.040975 L*/(1+ 0.01765 L*) unless L* 16 when SL= 0.511 SC= 0.0638 C*/(1 +

32、0.0131C*) + 0.638 SH= SC(FT + 1 - F) F = (C*)4/(C*)4+ 19000.5T = 0.36 + ABS 0.4 cos (h + 35) unless h is between 164 and 345 when T = 0.56 + ABS 0.2 cos (h + 168) When = c = l, the formula quantifies the perceptibility of color difference. Optimum values for and c may be determined for quantifying t

33、he acceptability of a color match. 8.5 CIE E*94This is a CIE recommendation on the practice of industrial color difference evaluation (25). It does not have the status of a CIE standard. The CIE 1976 (L*a*b*) color space (see 8.3) is retained as an approximate uniform color space representing percep

34、tion color magnitudes in terms of opponent color scales. The total color difference E*94between two color samples is a weighted Euclidean distance in CIE 1976 (L*a*b*) color space with rectangular color difference components; L*, C*ab, H*ab. A perceived color difference magnitude, V, is related to t

35、he total color difference through an overall sensitivity factor, KE. V = KE-1 E*94 SKH+ SKC+ SKL= EHH*ab2CCab2LL*20.5*94*Weighting functions SL, SC , SHadjust the total color difference equation to account for variation in perceived color difference magnitude with variation in the color standard loc

36、ation in color space. T 1215 sp-12 The determination of instrumental color differences / 6 SL= 1 SC= 1 + 0.045C*abSH= 1 + 0.015C*abParametric factors KL, KC , KHare correction terms for variation in perceived color difference component sensitivity with variation in experimental conditions. These par

37、ametric factors may be defined by industry groups to correspond to typical experimental conditions for that industry. The CIE E*94formula was derived from the CMC formula (see section 8.4), which is widely used in some industries, and is generally acknowledged to give better results than CIELAB for

38、correlation with visual assessment. 9. Keywords Color, Optical measurement, Optical instruments 10. Additional information 10.1 Effective date of issue: April 24, 2012. 10.2 This standard practice was formerly TIP 0804-04 and was revised in 1998. The 2007 version included only editorial changes. In

39、the 2012 version, the equation in 8.5 was corrected. Literature cited 1. Nickerson, D., Tables For Use in Computing Small Color Differences, ADR 39, 17 Aug. 1950 541-549. 2. BUC, G. L., Further Tables For Use in Computing Small Color Differences, ADR 41, 12 Jun 1952 353-355. 3. Davidson, H.R. & Hanl

40、on, J.J., Use of Charts Rapid Calculation of Color Difference, JOSA 45 1955, p. 617-620. 4. Simon, F. T., & Goodwin, W. J., Rapid Graphical Computation of Small Color Differences, ADR 47, Feb 1958, 105-112. 5. MacAdam, D.L., Visual Sensitivies to Color Differences in Daylight, JOSA 32 1942, 247-274.

41、 6. MacAdam, D.L., Specification of Small Chromaticity Differences, JOSA 33 1943, 18-26 7. Brown, W.R.J. & MacAdam, D.L., Visual Sensitivites to Combined Chromaticity and Luminance Differences, JOSA 39 1949, 808-834. 8. Adams, D., Derby, R. Jr., Ernsberger, R. & Solo, R., A Nomograph for Calculating

42、 Color Differences Using the Adams-Nickerson Equation, ADR 46, 18 Sjep 1957, 649-654. 9. Bridgeman, T., Inversions of the Munsell Value Equation, JOSA 53, 1963, 499. 10. Hardy, A.C., Handbook of Colorimetry, The Technology Press, MIT, Cambridge, Mass., 1936. 11. Judd, D.B. & Wyszecki, G., Color in B

43、usiness, Science & Industry, 3rd Ed., John Wiley & Sons, New York, N.Y. 1975. 12. Commission Internationale de lEclairage, CIE 1964 Color-Difference Formula, Colorimetry Official Recommendations of the International Committee of Illumination, CIE 15, 1971, 19. 13. Wyszecki, G., Recent Agreements Rea

44、ched by the Colorimetry Committee of the CIE, JOSA 58, 2 Feb 1968, 290-292. 14. Friele, L.F.C., Vos, J.J. & Walraven, P.L., Color Metrics, Proceedings of the Helmholtz Memorial Symposium on Color Metrics Held at Driebergen, The Netherlands, Sept. 1-3, 1971, AIC, Holland, 1972. 15. CIE Technical Comm

45、ittee TC-1.3 (Colorimetry) Communique, Proposal for Study of Uniform Color Spaces and Color-Difference Evaluations, March 5, 1974. 16. ISO/TC 38/SCI(Paris) Document 563E, Report of Working Group 7 Colour Measurement, October 1971. 17. AATCC Test Method 173-1990 “CMC“ calculation of Small Color Diffe

46、rences for Acceptability“ American Association of Textile Chemists and Colorists, Research Triangle Park, North Carolina 27709-2215 USA. 18. Wyszecki, G. & Stiles, W.S., Color Science, Concepts and Methods, Quantitative Date and Formulas, John Wiley & Sons, New York, N.Y., 1967. 19. Nickerson, D., S

47、ummary of Available Information on Small Color Difference Formulas, ADR 33 1944, 252-256. 20. American Society for Testing and Materials, Instrumental Evaluation of Color Differences of Opaque Materials, 7 / The determination of instrumental color differences T 1215 sp-12 ASTM Annual Stds., D2244. 2

48、1. CIE Publication No. 15, Supplement 2, Recommendations on Uniform Color Spaces, Color Difference Equations, Psychometric Color Terms, 1978. 22. Pauli, H., Proposed Extension of the CIE Recommendation on Uniform Color Spaces, Color Difference Equations, and Metric Color Terms, JOSA 66, 1976, 866-7.

49、 23. Clarke, F.J.J., R. McDonald and B. Rigg, Modification to the JPC79 Colour-Difference Formula, Journal of the Society of Dyers and Colourists, Vol. 100, 1984, p128-132 and p281-282. 24. McDonald, R., Acceptability and Perceptibility Decisions Using the CMC Colour Difference Formula, Textile Chemist and Colorist, Vol. 20, No. 6 1988, p31-37, and Errata, Vol. 20, No. 8, 1988, p10. 25. CIE Technical report 116-1995 Industrial Color Diff