ISO 5-3:2009 pdf free download – Photography and graphic technology一 Density measurements一 Part 3: Spectral conditions.
4.3 Types of instruments
Density measurements can be performed using two types of instrument, denoted as filter and spectral. A fully conforming filter instrument realizes the spectral product for the desired type of ISO 5 standard density, specified by Tables 2 to 7, by the appropriate combination of influx spectrum, given in 4.2, and spectral responsivity, usually achieved with a filtered detector. A filter instrument measures density directly. A spectral instrument measures the spectral transmittance or reflectance factor of a specimen and the desired type of ISO 5 standard density is calculated using the procedure specified in Annex B and the appropriate spectral weighting functions from Tables 8 to 13.
4.4 Spectral products
4.4.1 General
Spectral products, fl are obtained at each wavelength by multiplying the influx spectrum, S, by the spectral
responsivity, s.
4.4.2 Conformance
The spectral product of the densitometer (whether produced directly by a filter instrument or indirectly by calculation from a spectral instrument) shall be one of those specified in Tables 2 to 7. However, where greater accuracy is required, the 1 nm tables in the “Specprod.csv” file that forms an integral part of this part of ISO 5 may be used.
The spectral products at 10 nm intervals defined in Tables 2 to 7 provide the information necessary to define the spectral response of a “filter” instrument which claims conformance to this part of ISO 5. However, these data are not appropriate for calculation of ISO 5 standard density from spectral data. For this application, the methods specified in 4.5 shall be used.
NOTE The 10 nm spectral products specified in Tables 2 to 7 are defined in terms of logarithmic spectral product values specified at intervals of 10 nm, in order to be consistent with previous editions of this part of ISO 5. These are normalized to a peak value of 100 000. The logarithms to the base 10 of these values are used in this part of ISO 5 to define the various spectral types. The 1 nm spectral products are specified in the linear domain, normalized to a peak value of 1.
4.5 Computation of ISO 5 standard density from spectral data
4.5.1 General
When calculating ISO 5 standard density from spectral data, the measured spectral reflectance factor or spectral transmittance shall be multiplied by the spectral weighting factors appropriate for the measurement interval at which the data were collected.
4.5.2 Computation procedures
Computation of ISO 5 standard density shall be based on Simpson’s rule of numerical integration at 1 nm intervals, using the tables of spectral weighting factors identified in Annex A and contained in the “Specprod.csv” file. However, for practical measuring instruments, this result may be sufficiently approximated by using the abridged spectral weighting factors specified at 10 nm and 20 nm intervals contained in Tables 8 to 13 (and electronically in the “lOnmWeights.csv” and “2OnmWeights.csv” files) together with the computational techniques defined in Annex B. For the computation of abridged tables at other intervals, the method described in Annex D shall be used.