Designation:E1164–09a
Standard Practice for
Obtaining Spectrometric Data for Object-Color Evaluation1 This standard is issued under thefixed designation E1164;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.
INTRODUCTION
The fundamental procedure for evaluating the color of a reflecting or transmitting object is to obtain spectrometric data for specified illuminating and viewing conditions,and from these data to compute tristimulus values based on a CIE(International Commission on Illumination)standard observer and a CIE standard illuminant.The considerations involved and the procedures used to obtain precise spectrometric data are contained in this practice.The values and procedures for computing CIE tristimulus values from spectrometric data are contained in Practice E308.Considerations regarding the selection of appropriate illuminating and viewing geometries are contained in Guide E179.
1.Scope
1.1This practice covers the instrumental measurement re-quirements,calibration procedures,and material standards needed to obtain precise spectral data for computing the colors of objects.
1.2This practice lists the parameters that must be specified when spectrometric measurements are required in specific methods,practices,or specifications.
1.3Most sections of this practice apply to both spectrom-eters,which can produce spectral data as output,and spectro-colorimeters,which are similar in principle but can produce only colorimetric data as output.Exceptions to this applicabil-ity are noted.
1.4This practice is limited in scope to spectrometers and spectrometric colorimeters that employ only a single mono-chromator.This practice is general as to the materials to be characterized for color.
1.5The values stated in SI units are to be regarded as standard.No other units of measurement are included in this standard.
1.6This standard does not purport to address the safety concerns,if any,associated with its use.It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
2.Referenced Documents
2.1ASTM Standards:2
D1003Test Method for Haze and Luminous Transmittance of Transparent Plastics
E179Guide for Selection of Geometric Conditions for Measurement of Reflection and Transmission Properties of Materials
E259Practice for Preparation of Pressed Powder White Reflectance Factor Transfer Standards for Hemispherical and Bi-Directional Geometries
E275Practice for Describing and Measuring Performance of Ultraviolet and Visible Spectrophotometers
E284Terminology of Appearance
E308Practice for Computing the Colors of Objects by Using the CIE System
E387Test Method for Estimating Stray Radiant Power Ratio of Dispersive Spectrophotometers by the Opaque Filter Method
E805Practice for Identification of Instrumental Methods of Color or Color-Difference Measurement of Materials
E925Practice for Monitoring the Calibration of Ultraviolet-Visible Spectrophotometers whose Spectral Slit Width does not Exceed2nm
E958Practice for Measuring Practical Spectral Bandwidth of Ultraviolet-Visible Spectrophotometers
E991Practice for Color Measurement of Fluorescent
1This practice is under the jurisdiction of ASTM Committee E12on Color and
Appearance and is the direct responsibility of Subcommittee E12.02on Spectro-photometry and Colorimetry.
Current edition approved June1,2009.Published June2009.Originally approved in1987.Last previous edition approved in2009as E1164–09.
2For 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.
Copyright©ASTM International,100Barr Harbor Drive,PO Box C700,West Conshohocken,PA19428-2959,United States.
Specimens Using the One-Monochromator Method
E 1767Practice for Specifying the Geometries of Observa-tion and Measurement to Characterize the Appearance of Materials
E 2153Practice for Obtaining Bispectral Photometric Data for Evaluation of Fluorescent Color
E 2194Practice for Multiangle Color Measurement of Metal Flake Pigmented Materials 2.2NIST Publications:
LC-1017Standards for Checking the Calibration of Spec-trophotometers 3
TN-594-12Optical Radiation Measurements:The Translu-cent Blurring Effect—Method of Evaluation and Estima-tion 3
SP-260-66Didymium Glass Filters for Calibrating the Wavelength Scale of Spectrophotometers—SRM 2009,2010,2013,and 20143
SP-692Transmittance MAP Service 32.3CIE Publications:
CIE No.15.2Colorimetry,2nd edition 4
CIE No.38Radiometric and Photometric Characteristics of Materials and Their Measurement 4
CIE No.46Review of Publications on Properties and Reflection Values of Material Reflection Standards 4
CIE No.51Method for Assessing the Quality of Daylight Simulators for Colorimetry 4
CIE No.130Practical Applications of Reflectance and Transmittance Measurements 42.4ISO Publications:
ISO 2469Paper,Board and Pulps —Measurement of Diffuse Reflectance Factor 52.5ISCC Publications:
Technical Report 2003-1Guide to Material Standards and Their Use in Color Measurement 53.Terminology
3.1Definitions —The definitions contained in Terminology E 284are applicable to this practice.
3.2Definitions of Terms Specific to This Standard:
3.2.1influx ,n —the cone of light rays incident upon the specimen from the illuminator in a color measuring instrument (see Practice E 1767).
3.2.2efflux ,n —the cone of light rays reflected or transmit-ted by a specimen and collected by the receiver in a color measuring instrument (see Practice E 1767).
3.2.3regular transmittance factor,T r ,n —the ratio of the flux transmitted by a specimen and evaluated by a receiver to the flux passing through the same optical system and evaluated by the receiver when the specimen is removed from the system.3.2.3.1Discussion —In some cases,this quantity is practi-cally identical to the transmittance,but it may differ consider-ably.It exceeds unity if the system is such that the specimen causes more light to reach the receiver than would in its absence.
4.Summary of Practice
4.1Procedures are given for selecting the types and oper-ating parameters of spectrometers used to provide data for the calculation of CIE tristimulus values and other color coordi-nates to document the colors of objects.The important steps in the calibration of such instruments,and the material standards required for these steps,are described.Guidelines are given for the selection of specimens to minimize the specimen’s contri-bution to the measurement imprecision.Parameters are identi-fied that must be specified when spectrometric measurements are required in specific test methods or other documents.
5.Significance and Use
5.1The most general and reliable methods for obtaining CIE tristimulus values or,through transformation of them,other coordinates for describing the colors of objects are by the use of spectro
metric data.Colorimetric data are obtained by combining object spectral data with data representing a CIE standard observer and a CIE standard illuminant,as described in Practice E 308.
5.2This practice provides procedures for selecting the operating parameters of spectrometers used for providing data of the desired precision.It also provides for instrument calibration by means of material standards,and for selection of suitable specimens for obtaining precision in the measure-ments.
6.Requirements When Using Spectrometry
6.1When describing the measurement of specimens by spectrometry,the following must be specified:
6.1.1The relative radiometric quantity determined,such as reflectance factor,radiance factor,or transmittance factor.6.1.2The geometry of the influx and efflux as defined in Practice E 1767,including the following:
6.1.2.1For hemispherical geometry,whether total or diffuse only measurement conditions (specular component of reflec-tion included or excluded)are to be used.
6.1.2.2For bi-directional geometry,whether annular,cir-cumferential,or uniplanar measurement conditions are to be used,and the number,angle,and angular distribution of the multiple beams.
6.1.3The spectral parameters,including the wavelength range,wavelength measurement interval,and spectral band-pass or bandpass function in the case of variable bandpass.6.1.4Identification of the standard of reflectance factor,(see 10.2.1).
6.1.5The computation variables specified in Practice E 308,Section 6,including the standard observer and standard illu-minant,if their values must be set at the time of measurement,whether the spectral bandpass has been adjusted or not,and 6.1.6Special requirements determined by the nature of the specimen,such as the type of illuminating source for fluores-cent specimens (see Practice E 991)or the absolute geometric conditions and tolerances for retroreflective specimens.
3
Available from National Institute of Standards and Technology (NIST),100Bureau Dr.,Stop 1070,Gaithersburg,MD 20899-1070,v.4
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 01970,5
Available from International Organization for Standardization (ISO),1rue de Varembé,Case postale 56,CH-1211,Geneva 20,Switzerland,
www.iso.ch.
7.Apparatus
7.1Spectrometer —The basic instrument requirement is a spectrometer designed for the measurement of reflectance factor and,if applicable,transmittance factor,using one or more of the standard influx and efflux geometries for color evaluation described in Section 8.The spectrometer may be either a typical colorimetric spectrometer,designed specifically for the measurement of object color or a more traditional analytical spectrometer equipped with accessories for the output of the spectral values to a digital computer.
7.2Illuminator —For the measurement of nonfluorescent specimens,the exact spectral nature of the illuminator,of which the light source is a component,is immaterial so long as the source is stable with ti
me and has adequate energy at all wavelengths in the region required for measurement.Com-monly used light sources include incandescent lamps,either operated without filters or filtered to simulate CIE standard illuminants (see Publication CIE No.51),and flashed or continuous-wave xenon-arc lamps.More recently,discrete pseudo-monochromatic sources,such as light emitting diodes (LED)have also been used as sources in colorimetric spec-trometers.Considerations required when measuring fluorescent specimens are contained in Practice E 991.The use of pseudo-monochromatic sources is not currently recommended by Subcommittee E12.10for the measurement of the color of retroreflective materials.7.3Dispersive Element :
7.3.1The dispersive element,which separates energy in narrow bands of wavelength across the visible spectrum,may be a prism,a grating,or one of various forms of interference filter arrays or wedges.The element should conform to the following requirements:
7.3.2When highest measurement accuracy is required,the wavelength range should extend from 360to 830nm;other-wise,the range 380to 780nm should suffice.Use of shorter wavelength ranges may result in reduced accuracy.Each user must decide whether the loss of accuracy in his measurements is negligibly small for the purpose for which data are obtained.See Ref (1),6Practice E 308,and CIE No.15.2.
N OTE 1—Accuracy is here defined as agreement with results obtained by the use of the recommended measurement conditions and procedures.(1nm measurement interval with a 1nm spectral bandwidth and numerical summation of the data multiplied by CIE tabulated values at 1nm intervals).
7.3.2.1Fluorescent specimens should be measured with a wavelength scale beginning as close to 300nm as possible,if their characteristics when illuminated by daylight are desired.See Practice E 991.
7.3.3When highest accuracy is required,the wavelength measurement interval should be 1nm;otherwise,an interval of 5nm should suffice.Use of a wider interval,such as 10nm or 20nm,will result in a significant loss of accuracy.Each user must decide whether the loss of accuracy in his measurements is negligibly small for the purpose for which data are obtained.See Ref (1),Practice E 308,and CIE No.15.2.
7.3.4The spectral bandpass (width in nanometers at half energy of the band of wavelengths transmitted by the disper-sive element)should,for best results,be equal to the wave-length measurement interval or just slightly smaller than but no less than 80%of the wavelength measurement interval (2).If the spectral interval and bandpass are greater than 1nm then it is recomm
ended that the spectral data be interpolated and then deconvolved (21)down to the 1nm interval before computing tristimulus values as recommended in Practice E 308.
7.3.5The use of tables of tristimulus weighting factors (see Practice E 308)is a convenient means of treating data obtained for a shorter wavelength range than that specified in 7.3.2,or a wider measurement interval than that specified in 7.3.3,or both,for obtaining CIE tristimulus values.However,the use of a wider interval can lead to significant loss of measurement accuracy for specimens with reflectance or transmittance factors that change rapidly as a function of wavelength.Each user must decide whether the loss of accuracy in his measure-ments is negligibly small for the purpose for which data are obtained.
7.3.6For the measurement of nonfluorescent specimens,the dispersive element may be placed either between the source and the specimen or between the specimen and the detector.However,for the measurement of fluorescent specimens the dispersive element must be placed between the specimen and the detector so that the specimen is irradiated by the entire spectrum of the source.A still better method for characterizing fluorescent specimens is to use a bispectrometric method as described in Practice E 2153.
7.4Receiver —The receiver consists of the detector and related components.The detector may be a photoelectric device (phototube or photomultiplier),a silicon photodiode or diode array,or another suitable photodetector.The detector must be stable with time and have adequate responsivity over the wavelength range used.
8.Influx and Efflux Conditions
8.1Types and Tolerances —Unless special considerations requiring other tolerances are applicable,the instrument shall conform to the following geometric requirements,based on those proposed for the new revision of Publication CIE No.15.2,Publication CIE No.130,and following the notations contained in Practice E 1767,for the various types of reflectance-factor and transmittance factor measurements.In this specification,it is understood that each beam axis may be within 0.5°of the nominal direction,and each cone half-angle may be within 0.25°of the nominal value.
N OTE 2—With the possible exception of the measurement of unusually structured or fluorescent specimens,the same results will be obtained in each case by using the reciprocal geometric arrangement,that is,with the influx and efflux geometries interchanged.For example,the value of the reflectance factor obtained when illuminating the specimen with a hemispherical illuminator (such as a
n integrating sphere)and viewing it at an angle of 8°from the normal to the specimen surface will be the same as that obtained when illuminating the specimen at an angle of 8°and viewing it with a hemispherical receiver.In order to avoid implying unnecessary restrictions on instrumentation that can be used,when referencing this practice one should (except in those cases of fluorescent specimens for which it has been proven that reciprocity does not apply)make an explicit statement that reciprocal measurement conditions are
editor evaluating revision
6
The boldface numbers in parentheses refer to a list of references at the end of the
text.
permissible.The following paragraphs incorporate such a statement. 8.1.145°:Normal(45:0)and Normal:45°(0:45)Reflec-tance Factor—For the45°:normal condition,the specimen is illuminated by one or more beams each of whose nominal axes is at an angle of45°from the normal to the specimen surface. The angle between the direction of viewing and the normal to the specimen surface should not exceed0.5°.Generally,for obtaining excellent inter-instrument agreement,the instru-ments should have illumination beam cone nominal half-angles within2°of each other.The same restriction applies to
the viewing beam.Instruments that make their beam cone nominal half-angles all2°or less achieve this condition automatically. The same restriction applies to the viewing beam.When the illuminating beam is continuous and uniform throughout the 360°of azimuth,the condition is designated annular(45a:0). When many illuminating beams are provided at uniform intervals around the360°of azimuth,the condition is desig-nated circumferential(45c:0).When only one illuminating beam is used,or when there are two illuminating beams180°apart in azimuth,the condition is designated uniplanar(45x:0). Detailed descriptions of these geometries can be found in the appropriate sections of Practice E1767.For the normal:45°condition,the requirements for illumination and viewing are interchanged from those just described.
N OTE3—For certain applications of the45:0or0:45conditions, including measurement for formulation(8.2.1),significantly tighter toler-ances than those given in8.1.1may be required for the instrument angles of illumination and viewing,in order to ensure inter-instrument agree-ment.
8.1.2Total:Normal(di:8)or Diffuse:Normal(de:8or d:0) and Normal:Total(8:di)or Normal:Diffuse(8:de or0:d) Reflectance Factor—For the total:normal or diffuse:normal conditions,the specimen is illuminated diffusely by a hemi-spherical illuminator,such as an integrating sphere.The angle between the normal(perpendicular)to the surface of the specimen(the specimen normal)and the axis of the view
ing beam shall be8°62°.For some specific applications,such as that defined in ISO2469,the viewing angle is exactly0°and the tolerances described for8°apply similarly except where they may contradict the requirements of ISO2469.In general, spectral reflectance factor readings taken with de:8will not be in close agreement with those taken with d:0geometry.The short-hand notation for the ISO2469geometry does not include the lower case“e,”indicating exclusion of the specular component,as it is impossible to capture the efflux in a cone centered at0°and properly include the specular component. Thus there is only one mode of measurement possible for the d:0geometry.The illuminator may be of any diameter pro-vided the total area of the ports does not exceed5%of the internal reflecting area.The angle between the axis and any ray of the viewing beam should not exceed2°.When all regularly (that is,specularly)reflected light is included in the measure-ment,the condition is designated di:8;when all regularly reflected light is excluded,the condition is designated de:8or d:0.For the normal:total or normal:diffuse conditions,the requirements for illumination and viewing are interchanged from those just described.
N OTE4—Corrections for errors in the use of integrating spheres for the measurement of hemispherical reflectance factor have been discussed(3).
8.1.3Regular Transmittance of Fully Transparent Speci-mens,Free from Translucency,Diffusion,or Haz
e—The speci-men is illuminated by a beam whose effective axis is at an angle not exceeding5°from the specimen normal and with the angle between the axis and any ray of the illuminating beam not exceeding5°.The geometric arrangement of the viewing beam may be the same as that of the illuminating beam,or may differ,for example,by the use of a hemispherical receiver such as an integrating sphere.The requirements for illuminating and viewing may be interchanged.
N OTE5—When a hemispherical receiver such as an integrating sphere is used,and the specimen is placedflush against the transmission port of the sphere,(essentially)total transmittance factor is obtained.When the specimen is placed in the transmission compartment as far away from the sphere port as possible,(essentially)regular transmittance factor is obtained.
8.1.4Normal:Total(0:T t)or Normal:Diffuse(0:T d)and Total:Normal(T t:0)or Diffuse:Normal(T d:0)Transmittance Factor of Translucent,Diffusing,or Hazy Specimens—The characteristics of translucent,diffusing,or hazy specimens may be such that it is very difficult if not impossible to obtain measured transmittance factors that are device-independent, that is,independent of the details of the geometry and construction of the instrument used.Special precautions,out-lined here,must be observed to minimize the effects of these characteristics;the use of special equipment beyond the scope of this practice may be required to eliminate the effects entirely.
8.1.4.1The visual phenomena of translucency,diffuseness, or haze arise from diffusely scatteredflux within the specimens that can emerge through their sides or surfaces,often at locations significantly removed from the illuminated region of the specimen(4,5,and NBS TN-594-12).Unless these emergentfluxes are all measured,the indicated transmittance factor may be significantly low.
8.1.4.2General Influx and Efflux Conditions—For the nor-mal:total or normal:diffuse conditions,the specimen is illumi-nated by a beam whose effective axis is at an angle not exceeding2°from the specimen normal and with the angle between the axis and any ray of the illuminating beam not exceeding5°.The hemispherical transmittedflux is collected with a hemispherical receiver,such as an integrating sphere as described in Test Method D1003.When the reflectance of the receiver reflecting surface or other material at the point of impingement of the regularly transmitted beam,or at the point of impingement of the illuminating beam in the absence of a specimen,is identical to the reflectance of the remainder of the internal reflecting area of the receiver,the condition is desig-nated0:T t and the measurement provides the total transmit-tance factor(T t).When the regularly transmitted beam is excluded,for example by the use of a light trap,the condition is designated0:T d and the diffuse transmittance(T d)is ob-tained.Details of the size,shape,and reflectance of the light trap should be specified.The results of diffuse measurements made on specimens having broad regular-transmittance factor peaks will depend importantly on the size of the reflected beam and the size of the light
trap.
8.1.4.3A portion of the transmittedflux may be regularly transmitted and a portion diffusely transmitted.It is essential that these portions impinge on areas of the sphere wall having the same reflectance.If a white reflecting standard is used at the sample reflectance port,care must be taken to ensure that it has the same reflectance as the walls of the integrating sphere. Care must also be taken to avoid discoloring of either area due to prolonged radiation or dirt,or partial translucency due to insufficient thickness of the coating.
8.1.4.4In all measurements of translucent,diffusing,or hazy specimens,it is essential that the specimen be placedflush against the entrance port of the receiver,in order that all the flux emerging from the specimen enter the sphere.
8.1.4.5To further ensure that as much as possible of theflux traveling from side to side within the specimen is collected, either(1)illuminate a very small central area of the specimen and view it with a l
arge specimen port;or(2)uniformly illuminate a very large area of the specimen and measure a small central portion of it(4,5,and NBS TN-594-12).
8.1.4.6The requirements of8.1.4.5may be approximately met by use of a conventional integrating sphere with the largest possible illuminated area and the smallest possible viewed area,or the reverse.In such cases,it is recommended(5)to use the substitution method of measurement rather than the com-parison method(3).However,the substitution method intro-duces an error due to change in the sphere efficiency when the specimen is removed(substitution of“no sample”for sample). Care must be taken to correct for this error(3,Test Method D1003).
8.1.4.7The use of transmittance factor standards is recom-mended,provided that they are available with diffusing char-acteristics similar to those of the specimens being measured and are correctly calibrated using appropriate geometry(6,Test Method D1003).
8.1.4.8If instruments with conventional integrating spheres are used to measure translucent,diffusing,or hazy specimens, their measured transmittance factor will almost certainly be low and specific to the instrument and conditions used.
8.1.4.9For the total:normal and diffuse:normal conditions, the requirements for illumination and viewing
are interchanged from those just described.
N OTE6—For all the conditions described in8.1,the receiver should be arranged,with respect to both area and extent of angular acceptance,to view either considerably less than or considerably more than the entire beam emitted by the illuminator,so that the measurements are not sensitive to slight distortions of the beam by refraction in the specimen.
8.2Selection of Illuminating and Viewing Conditions—The following guidelines(7)may be useful for the selection of geometric conditions of illuminating and viewing for a variety of specimens and purposes.See also Guide E179and Practice E805.Geometric notations may be found in Practice E1767.
8.2.1For the formulation of product colors by computations involving Kubelka-Munk or other turbid-medium theory,either the bi-directional conditions(8)or the hemispherical diffuse conditions obtained by using an integrating sphere may be used.Special considerations for the interactions between an instrument geometry and the specimen surface are cited in the following sections and will also apply to the formulation of product colors.
8.2.2For assessing the color of highly glossy or fully matte specimens,the45:0or0:45conditions should
be used. Alternatively,the de:0or0:de conditions may be used,but different results may be obtained compared to those from the 45:0or0:45conditions or the de:8or the8:de conditions. 8.2.3For assessing the color of plane-surface low-gloss (matte)specimens,the8:de or de:8conditions(specular component excluded),or the di:8or8:di conditions(specular component included)may be used.Alternatively,the45:0or 0:45conditions or the0:de or de:0conditions may be used,but their use may lead to different results unless the specimens are perfectly Lambertian diffusers.
8.2.4For assessing the color of plane-surface specimens of intermediate gloss of textured-surface specimens,including textiles,where thefirst-surface reflection component may be distributed over a wide range of angles,the preferred geometry may have to be determined experimentally.Use of most geometries will not allow complete separation of the surface effects from the color.The preferred geometry will be the one that minimizes the surface effects,thereby optimizing the separation.The di:8or8:di conditions(specular component included)may be used,but it may be difficult to correlate visual judgements of the color to such measurements.
8.2.5When a specimen surface exhibits directionality,use of hemispherical,annular or circumferential geometry will provide data that may average over the effect.When the degree of directionality of the specimen is to be evaluated,uniplanar geometry should be used.The specimen should be measured at
two or more rotation angles45°apart to obtain the information on its directionality;alternatively,its rotation angle should be varied in successive measurements to obtain maximum and minimum instrument readings.The angles at which these readings occur should be noted in reference to the orientation of the specimen.When information on directionality is not required,the several measurements may be averaged.When the specimen does not exhibit directionality,any of the bi-directional geometries may be used.
8.2.6For the measurement offluorescent specimens,the 45:0or0:45conditions are normally required;see Practice E991.
8.2.7For the measurement of the daytime color of retrore-flective specimens,the45:0or0:45conditions are normally required.Some modern,high brightness,retroreflective sheet-ing has been shown to exhibit geometric artifacts if the cone angles are too narrow.In these cases,it may be more appropriate to use larger cone angles,with appropriate toler-ances.Subcommittee E12.10is working on this issue.
8.2.8For the measurement of materials pigmented with metallicflakes multiple angles of viewing are required.See Practice E2194.
9.Test Specimens
9.1Measurement results will not be better than the test specimens used in the measurements.Test specimens shall be representative of the materials being tested,and shall also conform to the following geometric and optical
requirements

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