ASTM E2152-12(2017)

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Designation: E2152 − 12 E2152 − 12 (Reapproved 2017)
Standard Practice for
Computing the Colors of Fluorescent Objects from
Bispectral Photometric Data
This standard is issued under the fixed designation E2152; 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 fluorescent specimen is to obtain bispectral
photometric data for specified irradiating and viewing geometries, and from these data to compute
tristimulus values based on a CIE (International Commission on Illumination) standard observer and
a CIE standard illuminant. Procedures for such computation are contained in this practice. This
practice also contains procedures for computing illuminant-specific spectral radiance factor values
from illuminant-independent bispectral photometric data.
1. Scope
1.1 This practice provides the values and practical computation procedures needed to obtain tristimulus values, designated X,
Y, Z and X , Y , Z for the CIE 1931 and 1964 observers, respectively, from bispectral photometric data for the specimen.
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Procedures for obtaining such bispectral photometric data are contained in Practice E2153.
1.2 Procedures for conversion of results to color spaces that are part of the CIE system, such as CIELAB and CIELUV are
contained in Practice E308.
1.3 This standard may involve hazardous materials, operations, and equipment. This 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 appropriate
safety safety, health, and healthenvironmental practices and determine the applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
E284 Terminology of Appearance
E308 Practice for Computing the Colors of Objects by Using the CIE System
E2153 Practice for Obtaining Bispectral Photometric Data for Evaluation of Fluorescent Color
2.2 CIE Standards:
CIE Publication 15.2,15 Colorimetry
2.3 ISO Standards:
ISO 11476 Paper and Board—Determination of CIE-Whiteness, C/2 Degrees
3. Terminology
3.1 Definitions—The definitions contained in Terminology E284 are applicable to this practice.
3.2 Definitions of Terms Specific to This Standard:
This practice is under the jurisdiction of ASTM Committee E12 on Color and Appearance and is the direct responsibility of Subcommittee E12.05 on Fluorescence.
Current edition approved July 1, 2012Nov. 1, 2017. Published September 2012November 2017. Originally approved in 2001. Last previous edition approved in 20062012
as E2152 - 01 (2006).E2152 – 12. DOI: 10.1520/E2152-12.10.1520/E2152-12R17.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from U.S. National Committee of the CIE (International Commission on Illumination), C/o Thomas M. Lemons, TLA-Lighting Consultants, Inc., 7 Pond St.,
Salem, MA 01970, http://www.cie-usnc.org.Illumination) at www.cie.co.at or www.techstreet.com.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2152 − 12 (2017)
3.2.1 bispectrometer, n—an optical instrument equipped with a source of irradiation, two monochromators, and a detection
system, such that a specimen can be measured at independently-controlled irradiation and viewing wavelengths. The
bispectrometer is designed to allow for calibration to provide quantitative determination of the bispectral radiation-transfer
properties of the specimen (1).
NOTE 1—Typically, a reference detection system monitors the radiation incident on the specimen. This reference detection system serves to compensate
for both temporal and spectral variations in the flux incident upon the specimen, by normalization of readings from the instrument’s emission detection
system.
3.2.2 diagonal elements, n—elements of a bispectral matrix for which irradiation and viewing wavelengths are equal.
3.2.3 fluorescence, n—this standard uses the term “fluorescence” as a general term, including both true fluorescence (with a
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luminescent decay time of less than 10 s) and phosphorescence with a delay time short enough to be indistinguishable from
fluorescence for the purpose of colorimetry.
3.2.4 off-diagonal element, n—any element of a bispectral matrix for which irradiation and viewing wavelengths are not equal.
4. Summary of Practice
4.1 Procedures—Procedures are given for computing from bispectral photometric measurements the CIE tristimulus values X,
Y, Z for the CIE 1931 standard observer and the CIE 1964 supplementary standard observer. While recognizing the CIE
recommendation of numerical integration at 1 nm intervals (in Publication 15.2) CIE 15) as the basic definition, this practice is
limited in scope to measurements and calculations using spectral intervals greater than or equal to 5 nm.
4.2 Calculations—CIE tristimulus values X, Y, Z or X , Y , Z are calculated by numerical summation of the products of
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weighting factors for selected illuminants and observers with the bispectral Donaldson radiance factor of the specimen. The
tristimulus values so calculated may be converted to coordinates in a more nearly uniform color space such as CIELAB or
CIELUV.
5. Significance and Use
5.1 The bispectral or two-monochromator method is the definitive method for the determination of the general radiation-transfer
properties of fluorescent specimens (2). In this method, the measuring instrument is equipped with two separate monochromators.
The first, the irradiation monochromator, irradiates the specimen with monochromatic light. The second, the viewing
monochromator, analyzes the radiation leaving the specimen. A two-dimensional array of bispectral photometric values is obtained
by setting the irradiation monochromator at a series of fixed wavelengths (μ) in the ultraviolet and visible range, and for each μ,
using the viewing monochromator to record readings for each wavelength (λ) in the visible range. The resulting array, once
properly corrected, is known as the Donaldson matrix, and the value of each element (μ,λ) of this array is here described as the
Donaldson radiance factor (D(μ,λ)). The Donaldson radiance factor is an instrument- and illuminant-independent photometric
property of the specimen, and can be used to calculate its color for any desired illuminant and observer. The advantage of this
method is that it provides a comprehensive characterization of the specimen’s radiation-transfer properties, without the
inaccuracies associated with source simulation and various methods of approximation.
6. Procedure
6.1 Selecting Standard Observer—Select standard observer according to the guidelines of Practice E308.
6.2 Selecting Illuminants—Select illuminants that are similar to the light under which the objects will be viewed or for which
their colors will be specified or evaluated. In general, follow the recommendations of Practice E308. For fluorescent samples,
however, special attention must be given to the relative UV content of the selected illuminants and the light under which the objects
will be viewed.
6.2.1 When object will be viewed indoors, by daylight filtered through a glass window, use values for the extended version of
Illuminant C defined in ISO 11476.
6.2.2 When object will be viewed outdoors, by unfiltered daylight, use values for CIE Illuminant D65, or other daylight
illuminants, as defined by the formulas developed by Judd, and presented in CIE 15.2.CIE 15.
6.2.3 When object will be viewed under well-defined special conditions of irradiation which are not similar to any standard
illuminant, a provisional illuminant may be defined. Such a provisional illuminant must represent the relative spectral irradiance
upon the object surface under these special conditions.
7. Calculation
7.1 Calculation of Colorimetric Quantities—Use the method of calculating tristimulus values at 5 nm intervals over the viewing
wavelength range 380 to 780 nm, and irradiation wavelength range 300 to 780 nm.
The boldface numbers in parentheses refer to a list of references at the end of this standard.
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7.2 Calculation of Tristimulus Values—The calculation procedures described below involve numerical summation of the
products of the Donaldson radiance factor of the specimen and a bispectral factor derived from the tabulated standard illuminant
and observer functions. After normalization, the sums are the CIE tristimulus values X, Y, Z (3, 2, 1).
7.2.1 Application of Illuminant Weights—Select the desired CIE standard illuminant from Tables given in Practice E308.
Multiply each element D(μ,λ) of the specimen’s Donaldson matrix by the tabulated value of the relative spectral power of the
illuminant Φ at the element’s irradiation wavelength (μ).
7.2.2 Calculation of Stimulus Function—Obtain the sum over μ of these products at 5 nm intervals over the wavelength range
300 to 780 nm. The sum obtained at each viewing wavelength λ is the value of the specimen’s stimulus function (relative spectral
radiance) F(λ), under the specified conditions of irradiation. From these values, either tristimulus values or spectral radiance factor
values may be derived.
F~λ!5 Φ~μ!D~μ,λ! (1)
(
μ5300
7.2.3 Derivation of Tristimulus Values—Use the color-matching functions selected in 6.1. Multiply the specimen’s stimulus
function at each viewing wavelength (λ) by the corresponding tabulated values of the observer color-matching functions. Obtain
the sum of these spectral products at 5 nm intervals over the wavelength range 380 to 780 nm:
X 5 k xH λ F λ (2)
~ ! ~ !
(
λ5380
Y 5 k yH~λ!F~λ!
(
λ5380
Z 5 k zH~λ!F~λ!
(
λ5380
where:
k = the normalization constant:
k 5 (3)
Φ~λ!yH~λ!
(
λ5380
7.3 Derivation of Other Colorimetric Quantities—Other colorimetric values, such as chromaticity coordinates, CIELAB and
CIELUV values, may be calculated from tristimulus values as described in Practice E308.
NOTE 2—The validity of CIELAB and CIELUV values for describing the color of fluorescent materials is subject to question, for two reasons. First,
because the appearance of a fluorescent material may be influenced by irradiation at wavelengths outside the visible range, the appropriate definition of
the “ white “white point” (incorporated in the CIELAB and CIELUV calculations) is not clear. Second, the perceptual uniformity of these color spaces
has not been evaluated in regions where L* exceeds 100, as it may for fluorescent materials. It is the responsibility of the user to determine the
appropriateness of such metrics for any particular specimen and application.
7.4 Derivation of Spectral Radiance Factors—Calculate the specimen’sspecimen’s stimulus function (relative spectral radiance)
F(λ) for the selected illuminant as described in section 7.2.2. Divide F at each viewing wavelength (λ) by the corresponding
tabulated value of the relative spectral power Φ of the selected illuminant. Note that for a fluorescent specimen, the spectral
I
radiance factor (β (λ) is illuminant-specific (3).
I
F λ Φ μ
~ ! ~ !
I I
β λ 5 5 D μ,λ (4)
~ ! ~ !
I (
Φ ~λ! Φ ~λ!
μ5300
I I
7.5 Separation of Fluorescence and Reflection Components—Fluorescence and reflection components of tristimulus and
spectral radiance factor values can be calculated by substituting the fluorescent or reflection components of Donaldson radiance
factor (D or D ) for Donaldson radiance factor (D) in the calculations described in sections 7.2 and 7.3. This separation of
F R
components is valid for D,β, and tristimulus values; it may not be valid for other colorimetric values.
7.5.1 Estimation of Components—To a first approximation, the contribution of fluorescence and reflectance to the appearance
of the specimen can be separated by treating diagonal values of the Donaldson matrix as representing reflectance only, and
off-diagonal values as representing fluorescence.
7.5.2 Calculation of Components—While more rigorous and accurate methods for the separation of reflection and fluorescence
components may be employed, description of such calculations lies outside the scope of this standard.
7.6 Abridged Calculation Procedures:
7.6.1 Wavelength Intervals of Greater than 5 nm—When data for D(μ,λ) are not available at 5 nm intervals, estimated values
at 5 nm intervals should be derived by appropriate interpolation, as described in Annex A1.
7.6.2 Viewing Wavelength Range Less Than 380-780 nm—When data for D(μ,λ) are not available for the full viewing
wavelength range, add the illuminant or observer weights, or both, at the wavelengths for which data are not available to the
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weights at the shortest and longest wavelength for which spectral data are available. Note that such use of spectrally-truncated data
is not recommended when significant fluorescent emission occurs in the region of truncation.
7.6.3 Irradiation Wavelength Range Less Than 300-780 nm—When the bispectral region of fluorescence is known for a
particular specimen, it is acceptable to limit the collection of fluorescence data (off-diagonal values) to this region. Complete the
standard Donaldson matrix by setting off-diagonal values outside this region to zero.
8. Report
8.1 The report of the measurement of colorimetric for fluorescent samples data shall include the following:
8.2 Specimen Description—Including the following:
8.2.1 Type and identification,
8.2.2 Date of preparation or manufacture, if required,
8.2.3 Method of cleaning and date, if cleaned,
8.2.4 Orientation of t
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