Designation:E308–08
Standard Practice for
Computing the Colors of Objects by Using the CIE System1 This standard is issued under thefixed designation E308;the number immediately following the designation indicates the year of original adoption or,in the case of revision,the year of last revision.A number in parentheses indicates the year of last reapproval.A superscript epsilon(´)indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the Department of Defense.
INTRODUCTION
Standard tables(Tables1-4)of color matching functions and illuminant spectral power distributions have since1931been defined by the CIE,but the CIE has eschewed the role of preparing tables of tristimulus weighting factors for the convenient calculation of tristimulus values.There have subsequently appeared numerous compilations of tristimulus weighting factors in the literature with disparity of data resulting from,for example,different selections of wavelength intervals and methods of truncating abbreviated wavelength ranges.In1970,Foster et al.(1)2proposed conventions to standardize these two features,and Stearns(2)published a more complete set of tables.Stearns’work and later publications such as the1985revision of E308have greatly reduced the substantial variations in methods for tristimulus computation that existed several decades ago.
The disparities among earlier tables were largely caused by the introduction of computations based on20-nm wavelength intervals.With the increasing precision of modern instruments,there is a likelihood of a need for tables for narrower wavelength intervals.Stearns’tables,based on a10-nm interval,did not allow the derivation of consistent tables with wavelength intervals less than10nm. The1-nm table must be designated the basic table if others with greater wavelength intervals are to have the same white point,and this was the reason for the1985revision of E308,resulting in tables that are included in the present revision as Tables5.
The1994revision was made in order to introduce to the user a method of reducing the dependence of the computed tristimulus values on the bandpass of the measuring instrument,using methods that are detailed in this practice.These changes,however,lead to tables(Tables6in this practice)that are substantially different from the Tables5that have been in use since1985.There is accordingly a danger,if the new tables are introduced but not universally adopted,that there may again be,perhaps for several decades,a significant disparity among the tables of tristimulus weighting factors commonly used.It is highly desirable that this should be avoided.
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1.1This practice provides the values and practical compu-tation procedures needed to obtain CIE tristimulus values from spectral reflectance,transmittance,or radiance data for object-color specimens.
1.2Procedures and tables of standard values are given for computing from spectral measurements the CIE tristimulus values X,Y,Z,and chromaticity coordinates x,y for the CIE 1931standard observer and X10,Y10,Z10and x10.y10for the CIE1964supplementary standard observer.
1.3Standard values are included for the spectral power of six CIE standard illuminants and three CIE
recommended fluorescent illuminants.
1.4Procedures are included for cases in which data are available only in more limited wavelength ranges than those recommended,or for a measurement interval wider than that recommended by the CIE.This practice is applicable to spectral data obtained in accordance with Practice E1164with 1-,5-,10-,or20-nm measurement interval.
1.5Procedures are included for cases in which the spectral data are,and those in which they are not,corrected for bandpass dependence.For the uncorrected cases,it is assumed that the spectral bandpass of the instrument used to obtain the data was approximately equal to the measurement interval and
1This practice is under the jurisdiction of ASTM Committee E12on Color and
Appearance and is the direct responsibility of Subcommittee E12.04on Color and
Appearance Analysis.
Current edition approved Dec.1,2008.Published January2009.Originally
approved in1966.Last previous edition approved in2006as E308–06.
2The boldface numbers in parentheses refer to the list of references at the end of
this practice.
Copyright©ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA19428-2959,United States.
was triangular in shape.These choices are believed to corre-spond to the most widely used industrial practice.
1.6This practice includes procedures for conversion of results to color spaces that are part of the CIE system,such as CIELAB and CIELUV (3).Equations for calculating color differences in these and other systems are given in Practice D 2244.
1.7The values stated in SI units are to be regarded as standard.No other units of measurement are included in this standard.
1.8This standard does not purport to address all of the safety concerns,if any,associated with its use.It is the responsibility 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 Documents 2.1ASTM Standards:3
D 2244Practice for Calculation of Color Tolerances and Color Differences from Instrumentally Measured Color Coordinates
E 284Terminology of Appearance
E 313Practice for Calculating Yellowness and Whiteness Indices from Instrumentally Measured Color Coordinates E 1164Practice for Obtaining Spectrometric Data for Object-Color Evaluation夺标800
E 2022Practice for Calculation of Weighting Factors for Tristimulus Integration 2.2ANSI Standard:
PH2.23Lighting Conditions for Viewing Photographic Color Prints and Transparencies 42.3CIE/ISO Standards:
辜鸿鸣CIE Standard S 001/ISO IS 10526,Colorimetric Illumi-nants 4,5
CIE Standard S 002/ISO IS 10527,Colorimetric Observ-ers 4,5
CIE Standard D 001,Colorimetric Illuminants and Observ-ers (Disk)5
2.4ASTM Adjuncts:
Computer disk containing Tables 5and 663.Terminology
3.1Definitions of terms in Terminology E 284are appli-cable to this practice (see also Ref (4)).3.2Definitions:
3.2.1bandpass ,adj —having to with a passband.
3.2.2bandwidth ,n —the width of a passband at its half-peak transmittance.
3.2.3chromaticity ,n —the color quality of a color stimulus definable by its chromaticity coordinates.
3.2.4chromaticity coordinates ,n —the ratio of each of the tristimulus values of a psychophysical color (see section 3.2.7.11)to the sum of the tristimulus values.
3.2.
4.1Discussion —In the CIE 1931standard colorimetric system,the chromaticity coordinates are:x =X /(X +Y +Z ),y =Y /(X +Y +Z ),z =Z /(X +Y +Z );in the CIE 1964supple-mentary colorimetric system,the same equations apply with all symbols having the subscript 10(see 3.2.7.).
3.2.5CIE ,n —the abbreviation for the French title of the International Commission on Illumination,Commission Inter-nationale de l’Éclairage.
3.2.6CIE 1931(x,y)chromaticity diagram ,n —chromaticity diagram for the CIE 1931standard observer,in which the CIE 1931chromaticity coordinates are plotted,with x as abscissa and y as ordinate.
3.2.7CIE 1964(x 10,y 10)chromaticity diagram,n —chromaticity diagram for the CIE 1964supplementary standard observer,in which the CIE 1964chromaticity coor-dinates are plotted,with x 10as abscissa and y 10as ordinate.3.2.7.1Discussion —Fig.1shows the CIE 1931and 1964chromaticity diagrams,including the locations of the spectrum locus and the connecting purple boundary.
3.2.8CIE 1976(u 8,v 8)or (u 810,v 810)chromaticity diagram,n —chromaticity diagram in which the CIE 1976L *u *v *(CIELUV)chromaticity coordinates are plotted,with u 8(or u 810)as abscissa and v
8(or v 810)as ordinate.
3.2.9CIE 1931standard colorimetric system ,n —a system for determining the tristimulus values of any spectral power distribution using the set of reference color stimuli,X,Y,Z and the three CIE color–matching functions x ¯(l ),y ¯(l ),z ¯(l )adopted by the CIE in 1931.大有
前途下载 3.2.10CIE 1964supplementary standard colorimetric sys-tem ,n —a system for determining the tristimulus values of any spectral power distribution using the set of reference color stimuli X 10,Y 10,Z 10and the three CIE color-matching func-tions x ¯10(l ),y ¯10(l ),z ¯10(l )adopted by the CIE in 1964(see Note 1).
N OTE 1—Users should be aware that the CIE 1964(10°)supplementary system and standard observer assume no contribution or constant contri-bution of rods to vision.Under some circumstances,such as in viewing highly metameric pairs in very low light levels (where the rods are unsaturated),the amount of rod participation can vary between the members of the pair.This is not accounted for by any trichromatic system of colorimetry.The 10°system and observer should be used with caution in such circumstances.
3.2.11color ,n —of an object ,aspect of object appearance distinct from form,shape,size,position or gl
oss that depends upon the spectral composition of the incident light,the spectral reflectance,transmittance,or radiance of the object,and the spectral response of the observer,as well as the illuminating and viewing geometry.
3.2.12color ,n —psychophysical ,characteristics of a color stimulus (that is,light producing a visual sensation of color)denoted by a colorimetric specification with three values,such as tristimulus values.
3.2.13color–matching functions ,n —the amounts,in any trichromatic system,of three reference color stimuli needed to
3
For referenced ASTM standards,visit the ASTM website,,or contact ASTM Customer Service at For Annual Book of ASTM Standards volume information,refer to the standard’s Document Summary page on the ASTM website.4
Available from American National Standards Institute (ANSI),25W.43rd St.,4th Floor,New York,NY 10036,5
Available from U.S.National Committee of the CIE (International Commission on Illumination),C/o Thomas M.Lemons,TLA-Lighting Consultants,Inc.,7Pond St.,Salem,MA 01970,6
Computer disk of 72tables is available from ASTM Headquarters.Request Adjunct No.
ADJE0308a.
match,by additive mixing,monochromatic components of an equal–energy spectrum.
3.2.14fluorescent illuminant ,n —illuminant representing the spectral distribution of the radiation from a specified type of fluorescent lamp.
3.2.15CIE recommended fluorescent illuminants ,n —a set of spectral power distributions of 12types of fluorescent lamps,the most important of which are F2,representing a cool white fluorescent lamp with correlated color temperature 4200K,F7,a broad-band (continuous-spectrum)daylight lamp (6500K),and F11,a narrow-band (line-spectrum)white fluorescent lamp (4000K).
3.2.16luminous ,adj —weighted according to the spectral luminous efficiency function V (l )of the CIE.
3.2.17opponent-color scales ,n —scales that denote one color by positive scale values,the neutral axis by zero value,and an approximately complementary color by negative scale values,common examples being scales that are positive in the red direction and negative in the green direction,and those that are positive in the yellow direction and negative in the blue direction.
3.2.18CIELAB color scales ,n —CIE 1976L *,a *,b *opponent-color scales,in which a *is positive in the red direction and negative in the green direction,and b *is positive in the yellow direction and negative in the blue direction.3.2.19CIELUV color scales ,n —CIE 1976L *,u *,v *opponent-color scales,in which u *is positive in the red direction and negative in the green direction,and v *is positive in the yellow direction and negative in the blue direction.
3.2.20passband ,n —a contiguous band of wavelengths in which at least a fraction of the incident light is selectively transmitted by a light-modulating device or medium.
3.2.21spectral ,adj —for radiometric quantities ,pertaining to monochromatic radiation at a specified wavelength or,by extension,to radiation within a narrow wavelength band about a specified wavelength.
3.2.22standard illuminant ,n —a luminous flux,specified by its spectral distribution,meeting specificati
ons adopted by a standardizing organization.
3.2.23CIE standard illuminant A ,n —colorimetric illumi-nant,representing the full radiator at 2855.6K,defined by the CIE in terms of a relative spectral power distribution.
3.2.24CIE standard illuminant C ,n —colorimetric illumi-nant,representing daylight with a correlated color temperature of 6774K,defined by the CIE in terms of a relative spectral power distribution.
3.2.25CIE standard illuminant D 65,n —colorimetric illumi-nant,representing daylight with a correlated color temperature of 6504K,defined by the CIE in terms of a relative spectral power distribution.
3.2.25.1Discussion —Other illuminants of importance de-fined by the CIE include the daylight illuminants D 50,D 55,and D 75.Illuminant D 50is used by the graphic arts industry for viewing colored transparencies and prints (see ANSI PH2.23).3.2.26standard observer ,n —an ideal observer having vi-sual response described by the CIE color-matching functions (see CIE S002and Ref (3)
).
FIG.1The CIE 1931x ,y and 1964x 10,y 10Chromaticity Diagrams Ref (5)(see Note 2
)
3.2.27CIE1931standard observer,n—ideal colorimetric observer with color-matching functions x¯(l),y¯(l),z¯(l) corresponding to afield of view subtending a2°angle on the retina;commonly called the“2°standard observer.”
3.2.28CIE1964supplementary standard observer, n—ideal colorimetric observer with color-matching functions x¯10(l),y¯10(l),z¯10(l)corresponding to afield of view subtend-ing a10°angle on the retina;commonly called the“10°standard observer”(see Note1).
3.2.29tristimulus values,n—see3.2.9and3.2.10.
3.2.30tristimulus weighting factors,Sx¯,Sy¯,Sz¯,n—factors obtained from products of the spectral po
wer S of an illuminant and the spectral color-matching functions x¯,y¯,z¯(or x¯10,y¯10, z¯10)of an observer,usually tabulated at wavelength intervals of 10or20nm,used to compute tristimulus values by multipli-cation by the spectral reflectance,transmittance,or radiance(or the corresponding factors)and summation.
3.2.30.1Discussion—Proper account should be taken of the spectral bandpass of the measuring instrument.
4.Summary of Practice
4.1Selection of Parameters—The user of this practice must select values of the following parameters:
4.1.1Observer—Select either the CIE1931standard colo-rimetric observer(2°observer)or the CIE1964supplementary standard observer(10°observer),tabulated in this practice, CIE Standard S002or D001,or Ref(3)(see3.2.26and Note 1).
4.1.2Illuminant—Select one of the CIE standard or recom-mended illuminants tabulated in this practice,CIE Standard S001or D001,or Ref(3)(see3.2.22).
4.1.3Measurement Interval—Select the measurement inter-val of the available spectral data.This practice provides for1-, 5-,10-,or20-nm measurement intervals.For best practice the measurement interval should be selected to be as nearly as possible equal to the instrument bandpass.
4.2Procedures—The user should ascertain whether or not the spectral data have been corrected for bandpass dependence. The accuracy of tristimulus values is significantly improved by incorporating a correction for bandpass dependence into either the spectral data or the tables of tristimulus weighting factors (see7.2).The procedures used depend on this and on the measurement interval.
4.2.1For data obtained at1-or5-nm measurement interval, the procedures of7.2should be followed.
4.2.2For data obtained at10-or20-nm measurement interval,the tables of tristimulus weighting factors contained in Tables5should be used with spectral data that have been corrected for bandpass dependence.The tables contained in Tables6should be used with spectral data that have not been so corrected;these tables include a provision that minimizes the error introduced by bandpass dependence when employing a triangular passband equal in half width to the measurement interval.
碱茅4.2.3Aflow chart to ensure the use of proper combinations of data and tables is given in Fig.2.The procedures of the practice are given in detail in7.1.
4.3Calculations—CIE tristimulus values X,Y,Z or X10,Y10, Z10are calculated by numerical summation of the products of tristimulus weighting factors for selected illuminants and observers with the reflectance factors(or transmittance or radiance factors)making up the spectral data.
4.4The tristimulus values so calculated may be further converted to coordinates in a more nearly uniform color space such as CIELAB or CIELUV.
5.Significance and Use
5.1The CIE colorimetric systems provide numerical speci-fications that are meant to indicate whether or not pairs of color stimuli match when viewed by a CIE standard observer.The CIE color systems are not intended to provide visually uniform scales of color difference or to describe visually perceived color appearances.
5.2This practice provides for the calculation of tristimulus values X,Y,Z and chromaticity coordinates x,y that can be used directly for psychophysical color stimulus specification or that can be transformed to nearly visually uniform color scales, such as CIELAB and CIELUV.Uniform color scales are preferred for research,production control,color-difference calculation,color specification,and setting color tolerances. The appearance of a material or an object is not completel
y specified by the numerical evaluation of its psychophysical color,because appearance can be influenced by other proper-ties such as gloss or texture.
6.Procedure
6.1Selecting Standard Observer—When colorimetric re-sults are required that will be compared with previous results obtained for the CIE1931standard observer,use the values in Table1for that observer.When new results are being com-puted,consider using the values in Table2for the CIE1964 supplementary standard observer,but see Note1.
6.1.1Whenever correlation with visual observations using fields of angular subtense between about1°and about4°at the eye of the observer is desired,select the CIE1931standard colorimetric observer.
6.1.2Whenever correlation with visual observations using fields of angular subtense greater than4°at the eye of the observer is desired,select the CIE1964supplementary stan-dard colorimetric observer(but see Note1).
6.2Selecting Standard or Recommended Illuminants—Select illuminants according to the type of light(s)under which objects will be viewed or for which their colors will be specified or evaluated.
6.2.1When incandescent(tungsten)lamplight is involved, use values for CIE illuminant A.
6.2.2When daylight is involved,use values for CIE illumi-nant C or D65.
6.2.3Whenfluorescent-lamp illumination is involved,use 4200K standard cool white(F2)unless results are desired for 6500K broad-band daylight(F7)or4000K narrow-band white (F11)fluorescent illumination.
6.3Selecting the Measurement Interval—For greater accu-racy select the5-nm measurement interval over the10-nm interval where spectral data are available at5-nm intervals. Likewise,select the10-nm measurement interval over the 20-nm interval where spectral data are available at10-nm intervals.If the20-nm interval is selected,users should
ensure
themselves that the resulting accuracy is sufficient for the purpose for which the results are intended.
For many industrial applications use of the 20-nm interval may be satisfactory.6.3.1If the instrument used has a selectable measurement interval,select the interval that most nearly equals the band-width of the instrument throughout the spectrum.If the instrument has an adjustable bandwidth,adjust the bandwidth to be approximately equal to the measurement interval.供热系数 6.3.2The measurement interval should be commensurate with the bandwidth.A much greater interval would under-sample the spectrum,and a much smaller interval would not improve the accuracy of the computation.
6.4Other Miscellaneous Conditions —While the above se-lections cover the majority of industrial practices,the possibil-ity exists that other conditions could be encountered.Further,the deconvolution routine used to produce Tables 6is not unique and uses approximating techniques that,while provid-ing overall a good approximation to the true value,may not in a specific instance provide the best approximation.Therefore,other procedures than those included in this practice may
be
N OTE 1—References to Section 7.Calculations are Included.
FIG.2Flow Chart for Selecting Methods and Tables for Tristimulus
Integration
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