ASTM E2729-16(2021)
(Practice)Standard Practice for Rectification of Spectrophotometric Bandpass Differences
Standard Practice for Rectification of Spectrophotometric Bandpass Differences
SIGNIFICANCE AND USE
5.1 Failure to make such a rectification introduces differences from the true value of the spectrum of about 0.02 to 0.4 ΔE*ab units. All users are required to make a rectification of such bandpass differences. It is especially incumbent upon writers of computer programs whose function it is to acquire such spectra from instruments to see that a competent rectification is implemented in the program before any additional processing of the spectrum, or calculations involving the spectrum are accomplished, or before the spectrum is made available to a user.
5.2 Legacy measuring systems are explicitly exempted from any requirements for retrofitting of hardware or software and may continue to utilize previously accepted methods of making the bandwidth rectification.
SCOPE
1.1 This standard outlines the methods that can be used to deconvolve, at least partially, the spectral bandpass differences of raw spectral data acquired by abridged spectrophotometry. Such differences are introduced because the spectral passband must be of significant bandwidth to allow sufficient energy to reach the detector. On the other hand, the spectral data that should be reported is that of a virtual 1-nm bandwidth spectrum in order to be useful in the CIE method of tristimulus integration which involves 1-nm summation.
1.2 The standard establishes practices for whether, when, and how a bandpass rectification should be made to any reflectance or transmittance spectrum acquired by abridged spectrophotometry.
1.3 It is applicable where the shape of the passband is triangular and the bandwidth is equal to the measurement interval between passbands. Information is provided in Section 7 for users when that condition is not satisfactorily met.
1.4 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.5 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.
General Information
Relations
Standards Content (Sample)
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.
Designation: E2729 −16 (Reapproved 2021)
Standard Practice for
Rectification of Spectrophotometric Bandpass Differences
This standard is issued under the fixed designation E2729; 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.
1. Scope E308 PracticeforComputingtheColorsofObjectsbyUsing
the CIE System
1.1 This standard outlines the methods that can be used to
deconvolve, at least partially, the spectral bandpass differences
3. Terminology
of raw spectral data acquired by abridged spectrophotometry.
3.1 Definitions—For definition of terms used in this
Such differences are introduced because the spectral passband
practice, refer to Terminology E284.
must be of significant bandwidth to allow sufficient energy to
reach the detector. On the other hand, the spectral data that
3.2 Definitions of Terms Specific to This Standard:
shouldbereportedisthatofavirtual1-nmbandwidthspectrum
3.2.1 virtual 1-nm bandwidth spectrum, n—spectral data
in order to be useful in the CIE method of tristimulus
that have been corrected by numerical methods so as to match
integration which involves 1-nm summation.
ascloselyaspossibleaspectrumfromthesamesourcebutwith
a putative bandwidth of 1 nm.
1.2 The standard establishes practices for whether, when,
and how a bandpass rectification should be made to any
4. Summary of Practice
reflectance or transmittance spectrum acquired by abridged
spectrophotometry. 4.1 The practice assumes that the shape of the passband is
triangular and that the bandwidth is equal to the measurement
1.3 It is applicable where the shape of the passband is
intervalbetweenpassbands.Thisconditionisthoughttobemet
triangular and the bandwidth is equal to the measurement
by a majority of commercial instruments in use in spectropho-
interval between passbands. Information is provided in Section
tometry and spectrocolorimetry. Under those conditions, the
7 for users when that condition is not satisfactorily met.
methods of Section 6 are to be utilized to rectify the raw
1.4 This standard does not purport to address all of the
reflectance or transmittance data for its bandpass differences
safety concerns, if any, associated with its use. It is the
immediately upon the return of the data to the host computer
responsibility of the user of this standard to establish appro-
program from the acquiring instrument, or before presentation
priate safety, health, and environmental practices and deter-
of the data to the user.
mine the applicability of regulatory limitations prior to use.
1.5 This international standard was developed in accor-
5. Significance and Use
dance with internationally recognized principles on standard-
5.1 Failure to make such a rectification introduces differ-
ization established in the Decision on Principles for the
ences from the true value of the spectrum of about 0.02 to 0.4
Development of International Standards, Guides and Recom-
∆E* units. All users are required to make a rectification of
ab
mendations issued by the World Trade Organization Technical
such bandpass differences. It is especially incumbent upon
Barriers to Trade (TBT) Committee.
writers of computer programs whose function it is to acquire
such spectra from instruments to see that a competent rectifi-
2. Referenced Documents
cation is implemented in the program before any additional
2.1 ASTM Standards:
processing of the spectrum, or calculations involving the
E284 Terminology of Appearance
spectrum are accomplished, or before the spectrum is made
available to a user.
5.2 Legacymeasuringsystemsareexplicitlyexemptedfrom
This practice is under the jurisdiction of ASTM Committee E12 on Color and
Appearance and is the direct responsibility of Subcommittee E12.04 on Color and
any requirements for retrofitting of hardware or software and
Appearance Analysis.
maycontinuetoutilizepreviouslyacceptedmethodsofmaking
Current edition approved June 1, 2021. Published June 2021. Originally
the bandwidth rectification.
approved in 2009. Last previous edition approved in 2016 as E2729 – 16. DOI:
10.1520/E2729-16R21.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or 6. Methodology
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
6.1 The First and Last Passbands—In the first and last
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. passband being rectified, no correction is called for. The
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2729 − 16 (2021)
corrected spectral value R should be set equal to the above correction is among the best practices for making a
s,λ
measured spectral value R . rectification of bandpass differences.
m,λ
R 5 R (1) 7.2 While the underlying theory leading to the rectification
s,1 m,1
equations is based on triangular passbands, some related
R 5 R
s,n m,n
bandpass shapes may be adequately rectified by the methods of
this practice. This is true of Gaussian and Lorentzian function
where the subscripts 1 andn refer to the wavelength index of
band shapes, and may be true of instruments with concave
the first and last passbands being corrected.
diffraction gratings imaged on diode arrays with more pixels
6.2 The Second and Next-to-last Passbands—The second
than wavelengths being reported. Those passbands are trap-
and next-to-last passbands being rectified are subject to the
ezoidal in shape.
following correction:
7.3 If the user has specific knowledge as to departures from
R 520.10R 11.21R 2 0.12R 10.01R (2)
s,2 m,1 m,2 m,3 m,4
the above assumptions with respect to his particular measure-
ment conditions, he may calculate a set of correction coeffi-
R 520.10R 11.21R 2 0.12R 10.01R
s,n21 m,n m,n21 m,n22 m,n23
cients fitting his own case from principles laid down in the
where the second subscript refers to the wavelength index of
published literature. Most helpful in this regard will be articles
the bandpass considered.
by Stearns (1,2), Fairman (3), Oleari (4),Venable (5), Gardner
(6), and Ohno (7). Corrections using such coefficients are
6.3 The Remaining Interior Passbands—The remaining in-
deemed to meet the requirements of this practice.
terior passbands are subject to the following five-point rectifi-
cation:
8. Precision and Bias
R 5 0.01R 2 0.12R 11.22R 2 0.12R 10.01R
s,i m,i22 m,i21 m,i m,i11 m,i12
8.1 The rectification has no impact on the precision of any
(3)
test method.
wherethesubscriptiisthewavelengthindexofthepassband
8.2 In the absence of any rectification, the bias introduced
being
...
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