ASTM E2729-16(R2021) pdf free download

ASTM E2729-16(R2021) pdf free download.Standard Practice for Rectification of Spectrophotometric Bandpass Differences
1. 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 ofa 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 appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.5 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
4. Summary of Practice
4.1 The practice assumes that the shape of the passband is triangular and that the bandwidth is equal to the measurement interval between passbands. This condition is thought to be met by a majority of commercial instruments in use in spectropho- tometry and spectrocolorimetry. Under those conditions, the methods of Section 6 are to be utilized to rectify the raw reflectance or transmittance data for its bandpass differences immediately upon the return of the data to the host computer program from the acquiring instrument, or before presentation of the data to the user.
5. Significance and Use
5.1 Failure to make such a rectification introduces differ- ences from the true value of the spectrum .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 rectifi- cation 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 ofmaking the bandwidth rectification.
7. Applicable Bandpass Shapes
7.1 The coefficients of the foregoing rectification equations have been calculated under the assumption that the passbands are spaced at equal intervals. The interval is assumed to be equal to the full-width half-height of the passbands. Further, assumption is made that the passbands are triangular in shape and that the reflectance, or transmittance, functions may be characterized by a quadratic function in the range of any passband. These assumptions are believed to be true for most instruments, materials, and measurements known to the Sub- committee with jurisdiction for this practice. Accordingly, the above correction is among the best practices for making a rectification of bandpass differences. 7.2 While the underlying theory leading to the rectification equations is based on triangular passbands, some related bandpass shapes may be adequately rectified by the methods of this practice. This is true of Gaussian and Lorentzian function band shapes, and may be true of instruments with concave diffraction gratings imaged on diode arrays with more pixels than wavelengths being reported. Those passbands are trap- ezoidal in shape.