This standard establishes methods for measuring the reflectance and transmission spectra and calculating the colorimetric parameters of printed images by printing methods such as lithography, relief printing, gravure and stencil printing. This standard does not apply to three-color filter (tristimulus value) colorimeters, although Annexes B, D, E, F and G may refer to such instruments. This standard applies to color images reproduced in limited batches by photography, inkjet, thermal transfer, diffusion, electrostatic photography, mechanical transfer toner (offline proofing) and other technologies. This standard does not involve the measurement of the emission spectrum of video monitors, nor can it replace the specification requirements of other measurement geometries applicable to special application needs, such as the evaluation of printing materials (inks, paper). GB/T 19437-2004 Printing technology Spectral measurement and colorimetric calculation of printed images GB/T19437-2004 Standard download decompression password: www.bzxz.net
This standard establishes methods for measuring the reflectance and transmission spectra and calculating the colorimetric parameters of printed images by printing methods such as lithography, relief printing, gravure and stencil printing. This standard does not apply to three-filter (tristimulus) colorimeters, although Appendices B, D, E, F, and G may refer to such instruments. This standard applies to limited batch reproduction of color images obtained by photography, inkjet, thermal transfer, diffusion, electrophotography, mechanical transfer toner (off-line proofing), etc. This standard does not cover the measurement of the emission spectrum of video monitors, nor can it replace the specification requirements of other measurement geometries applicable to special application needs, for example, evaluation of printed materials (inks, paper).

This standard is proposed and managed by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China. The drafting unit of this standard is Beihai Entry-Exit Inspection and Quarantine Bureau. The main drafters of this standard are Xiao Huanxin, He Liu, Li Yiming, Wu Junyi and Yin Jixian. GB/T19468—2004
GB/T19437—2004/IS013655:1996 Introduction
There are many customary practices for spectral measurement and colorimetric calculation in CIE publication 15.2. The geometric structure of the instrument, the illuminant, the observer angle and other conditions are selected by the user. However, this choice will result in different values ​​for the same parameters of the same material. Moreover, the measurement made by one method cannot usually be converted into the corresponding value of another method. Therefore, the data obtained by different methods are not comparable. The purpose of this international standard is to determine a measurement method for printed images that can produce valid and comparable data. Although this international standard refers to some standards established for the observation conditions of printed images, it does not attempt to provide an absolute correlation for visual color representation.
1 Scope
Printing technology
GB/T19437—2004/ISO13655:1996 Spectral measurement and colorimetric calculation of printed images This standard establishes methods for measuring the reflectance and transmission spectra and calculating the colorimetric parameters of printed images printed by lithographic, relief, gravure and screen printing methods. This standard does not apply to three-color filter (tristimulus value) colorimeters, although Annexes B, D, E, F and G may refer to such instruments. This standard applies to color images reproduced in limited batches obtained by photography, inkjet, thermal transfer, diffusion, electrostatic photography, mechanical transfer, toner (offline proofing) and other technologies.
This standard does not involve the measurement of the emission spectrum of video monitors, nor can it replace the specification requirements of other measurement geometric conditions applicable to special application needs, such as the evaluation of printing materials (inks, paper). Note 1: The measurement method of the spectral data of video monitors can be found in ASTM E1336-1991 L4}, and the evaluation method of paper using integrating sphere geometry can be found in ISO 2469 [2].bZxz.net
2 Normative references
The clauses in the following documents become clauses of this standard through reference in this standard. For any dated referenced document, all subsequent amendments (excluding errata) or revisions are not applicable to this standard. However, parties to an agreement based on this standard are encouraged to investigate whether the latest versions of these documents can be used. For any undated referenced document, the latest version applies to this standard. ISO 5-2 Photography — Density measurement — Part 2: Geometric conditions for transmission density (ISO 5-2:1991) ISO 5-4 Photography — Density measurement — Part 4: Geometric conditions for reflection density (ISO 5-4:1995) ISO 3664 Photography — Illumination conditions for viewing color transmission photographs and their reproductions (ISO 3664:1975) CIE Publication 15.2 Colorimetry
3 Definitions and abbreviations
For the purposes of this standard, the following definitions and abbreviations apply. 3.1
International Commission on Illumination.
CIE illuminants CIE illuminants
Illuminants A, Dso, Ds and other illuminants D defined by CIE with relative spectral power distribution. 3.3
Illuminant
Radiance with a defined relative spectral power distribution over the entire wavelength range that affects the color perception of objects. 3.4
measurement illuminant
measurement illuminant
radiant luminous flux characteristics incident on the sample surface. 3.5
radiance factor
the ratio of the radiance of the object surface to the radiance of a completely diffuse reflecting surface or a completely diffuse transmitting surface under specific lighting and observation conditions. 1
GB/T19437--2004/IS013655:19963.6
reflectance factor
the ratio of the reflected luminous flux measured from the printed sample to the reflected luminous flux measured from a completely diffuse reflector at the same position. 3.7
sample backing
the plane on which the sample to be tested is placed.
Transmittance factorThe ratio of the luminous flux through the measuring aperture covered by the sample to the luminous flux when the aperture is not covered by the sample. 3.9
Bandwidth
The width between the half-energy points on the spectral response function curve. Note 2: The spectral measurement instrument uses a triangular characteristic function. 4 Spectral measurement conditions
4.1 Instrument calibration
The measuring instrument should be calibrated according to the method in the product manual. The calibration method provided by the manufacturer should follow the relevant regulations of the national standardization agency.
Note 3: When measuring with multiple instruments, the measurement data will be different due to differences in instrument characteristics. Appendix H provides a method to make these data close to the same. This method can be used for spectrophotometric measurements of reflection and transmission. 4.2 Measuring the spectral energy distribution of the light source
4.2.1 Non-fluorescent materials
If the material to be measured does not fluoresce, there is no special requirement for measuring the spectral energy distribution of the light source. Therefore, no detailed description of the spectral power distribution of the measuring light source consistent with the illuminant in 5.1 is given. 4.2.2 Fluorescent materials
In order to minimize the difference in measurement results between measuring instruments due to fluorescence, the spectral power distribution of the measuring light source shall match the CIE illuminant Dso specified in 5.1 in the wavelength range of energy absorption and emission. NOTE 4: At present, many instruments do not have a measuring light source consistent with Ds. Appendix G provides further technical information on fluorescence and testing for the presence of fluorescence.
4.3 Wavelength range and wavelength intervals
The data shall be measured from 340nm to 780nm, with measurement intervals of 10nm, and shall at least include the wavelength range of 400nm to 700nm, and the measurement interval shall not exceed 20nm. The reference spectral data shall be based on the calculated data with 10nm intervals, and its spectral response function shall be a triangular wave with 10nm intervals.
NOTE 5: Different instruments will produce different results due to different intervals or response functions. This error can be reduced by choosing the appropriate bandpass shape within the wavelength interval and using the appropriate bandpass characteristics and the calculation method for the appropriate wavelength interval. 4.4 Measurement of reflectance
4.4.1 Sample backing material
The backing material should be placed under or behind the sample during measurement as specified in 4.7 of ISO 5-4:1995 to eliminate the influence of different backgrounds and the color printed on the back of the sample. See Annex D. 4.4.2 Measurement geometry
The measurement geometry is 45°/0° or 0/45° and complies with the relevant geometry specified in ISO 5-4. NOTE 6: If the 45°/0° or 0/45° geometry cannot fully reflect all the characteristics of the sample surface, other instruments can be used to measure special characteristics of the sample surface, such as "gloss", see Annex E.
NOTE 7: Due to the physical size of the printed color standard usually measured, many instruments do not meet the ISO 5-4 requirement that the illuminated area of ​​the sample is larger than the sampling aperture by 2 mm. Annex F provides further information on aperture sizes. 2
4.4.3 Measurement Record
GB/T19437—2004/ISO13655:1996 A perfect diffuse reflector has 100% reflectivity at all wavelengths, so the reflectance coefficient measured relative to a perfect diffuse reflector should be multiplied by 100 and accurate to 0.01% or an equivalent decimal. 4.5 Measurement of Transmittance
4.5.1 Measurement Geometric Conditions
The measurement geometric conditions are vertical/diffuse (0°/d) or diffuse/vertical (d/0°) and conform to the geometric conditions specified in ISO5-2 or CIE15.2.
The measurement geometric conditions and the integrating sphere or opalescent diffuser used should be stated (see Appendix E). 4.5.2 Measurement Record
A completely diffuse transmittance has 100% transmittance at all wavelengths, so the transmittance coefficient measured relative to the completely diffuse transmittance should be multiplied by 100 and accurate to 0.01% or an equivalent decimal (see Appendix E). 5 Chromaticity Calculation Conditions
5.1 Calculation of Tristimulus Values
In order to be consistent with the printed image observation conditions specified in ISO3664, the tristimulus values ​​should be calculated based on the CIEDso illuminant and CIE Publication 15.2 (commonly known as the 2° standard field of view). The calculation should be done with a wavelength interval of 10nm or 20nm. Tables 1 and 2 list the products of the CIEDso illuminant and the 2° standard field of view, with intervals of 10nm and 20nm, respectively, as the weighting coefficients of the spectral reflectance and transmittance coefficients when calculating the tristimulus values. The data is from ASTM E308 [3]. It is strongly recommended to use a 10nm interval to improve the accuracy of the calculation.
Note 8: The 2° field of view is chosen instead of the 10° field of view because it better matches the size of the image detail range observed by the human eye. If the measured spectral data uses a wavelength greater than 340nm as the starting wavelength, then all weighting coefficients less than the starting measurement wavelength in Tables 1 and 2 should be combined and added to the weighting coefficient of the starting wavelength. If the end measurement wavelength is less than 780nm, then all weighting coefficients greater than the end measurement wavelength in Tables 1 and 2 should be combined and added to the weighting coefficient of the end wavelength. The general form of
calculation is:
Z[R(a) · Wx(A)]
Yr(a) . Wy(a)]
Z-\ER(a) ·W2(a)
Where:
R(a)—
T(a)—
reflection coefficient when the wavelength is the input;
transmission coefficient when the wavelength is the input;
X-[T(a) Wx(A))
ET() · Wy(A))
Z(T(a) · Wz(a)]
Wx()—weighting coefficient for the tristimulus value X at wavelength input; Wy(a)
Wz(>)—weighting coefficient for the tristimulus value Y at wavelength input; weighting coefficient for the tristimulus value B at wavelength input. If the measurement interval and bandpass are less than 10nm, the bandpass of the data can be expanded using the method in Appendix A. Note 9: The weighting coefficients given in Tables 1 and 2 are based on the triangular bandpass characteristics described in 4.3. The data X, = 96.422, Y, = 100.00, Z, = 82.521 are used for chromaticity calculations. Note 10: In Tables 1 and 2, the sum of the weighting coefficients from 340nm to 780nm is not equal to the values ​​of X, Y, and Z, because X, Y, and Z are calculated according to ASTME308 , which is more accurate than the values ​​given in the table. The sum of X, Y, and Z in the table can be used to verify the data in the table. 3
GB/T19437-2004/1S013655:1996Table 11
Weighting coefficients for calculating tristimulus values ​​under Dso illumination and 2° field of view observation conditions (interval 10nm) Wavelength/nm
Wavelength/nm
Table 1 (continued)
GB/T19437-2004/ISO13655:1996Wz(a)
2Weighting coefficients for calculating tristimulus values ​​under Dso illumination and 2° field of view observation conditions (interval 20nm)Table 2
Wavelength/nm
Note: Although the table provides weighting coefficients at intervals of 20nm, it is recommended to use 10 Data at nm intervals are used to improve the accuracy of calculations. 5
GB/T19437—2004/IS013655:1996 Note 11: It is convenient to use the CIE Dss illuminant, but it is inconsistent with this standard. For ease of application, Appendix C lists the weighting coefficients used to calculate the tristimulus values ​​under the conditions of the CIE Das illuminant and the CIE1931 standard colorimetric observer (usually referring to a 2° field of view). Note 12: Tables 1 and 2, Tables C.1 and C.2 are taken from the ASTM Standards Manual with permission. Copyright is the American Society for Testing and Materials (1916 Race St. Philadelphia, PA 19130. USA). 5.2 Calculation of other chromaticity parameters
Chromaticity parameters should be calculated using the formulas given in CIE Publication 15.2. Appendix B provides the formulas for calculating CIEL, A, B, *, a*, b", C, ha and the related color difference formulas and CMC color difference formula. 5.3
3 Data Records
When recording data generated in accordance with this standard, the following information should be attached: a)
Confirmation that the measurement and calculation comply with this standard;
Data processor;
Date of data recording;
State the purpose or content of the exchanged data;
State the The instruments used, including but not limited to the brand and model of the instruments; the application conditions of the measurement source (light source and color filter); the wavelength interval used.
Appendix A
(Normative Appendix)
Bandwidth expansion method for narrow-bandpass instruments
The spectral measurement tristimulus value integration method described in the text of GB/T19437--2004/ISO13655:1996 standard uses a 10nm or 20nm bandwidth instrument. The tristimulus value integration method assumes that the instrument has a bandwidth of The bandwidth and sampling interval are approximately equal (a sampling interval of 10nm assumes a bandwidth of 10nm, and a sampling interval of 20nm assumes a bandwidth of 20nm). The bandwidth is usually defined as the half-energy point of the triangular response function of the measuring instrument. This assumption is based on the design of traditional laboratory instruments using slit apertures, diffraction gratings or prisms. When the sampling interval does not meet the required 10nm or 20nm, the data must be corrected (resampled) to provide estimated (or approximate) data obtained at the required interval. This correction method should only be done when the sampling interval is less than 10nm or 20nm and the bandwidth is consistent with the sampling interval.
According to the required (new) sampling interval and bandwidth, the collected data is processed in turn with the triangular characteristic weighting function, and then the data is summed within the sampling interval and normalized based on the sum of the weighted values ​​to obtain the new bandwidth-widened data. This process is repeated for each new data point. The weighting coefficient is as follows:
dl ay, ax,
W(ax,) = 4
W(ax.)——weighting coefficient for wavelength x,; in y. —wavelength of data to be calculated (wavelength of new data); in x,——wavelength of existing data (wavelength of instrument measurement data);——required bandwidth.
The definition interval of this function is: 1, ax, "<. When the data at the end of the measurement range cannot be obtained, it is assumed that this section of data is uniform, and the last point of measurement data is used as the endpoint value. Note 13: The following example assumes that the data collected at intervals of 3nm are to be converted into data at intervals of 10nm that meet the requirements. Then, the specific values ​​near 420nm are at wavelengths of 403nm, 406nm, 409nm436nm. The data at 420nm is calculated as follows: 1 Because the bandwidth (△^) is 10nm, only the data between 410nm and 430nm are used for calculation (i.e.: data at 412, 415, 418, 421, 424, 427 and 430nm).
2 According to the above formula, the weighting coefficients are 412 (0.2), 415 (0.5), 418 (0.8), 421 (0.9), 424 (0.6), 427 (0.3) and 430 (0). The sum of the weighting coefficients is 3.3.
3 The spectral data of each wavelength X is multiplied by its corresponding weighting coefficient, the products are summed, and then divided by the sum of the weighting coefficients (3.3 in this case). This is the new data corresponding to the 10nm bandpass and the central wavelength of 420nm. 4 Repeat this process in the wavelength range of 340nm to 780nm with an interval of 10nm. This method can also be used to modify the data obtained with other intervals to provide weighting coefficients with intervals of 10nm or 20nm for chromaticity calculation.
GB/T 19437--2004/ISO13655:1996 Appendix B
(Informative Appendix)
Calculation of CIELAB, CIELUV and CMC(I : c) parameters B.1 CIELAB chromaticity parameters (see CIE Publication 15.2) L* -- 116[f(Y/Y,)J—16
a\ =500[f(X/X,)-f(Y/Y.)]
6* =200f(Y/Y,)- f(Z/Z.)J
When:X/X,>0.008 856,f(X/X,)=(X/X,)1/3Y/Y.>0.008 856, f(Y/Y,)=(Y/Y,)1/3Z/Z,>0.008 856, f(Z/Z,)=(Z/Z.)1/3 when:008856, f(Y/Y.)7.7867(Y/Y,)+16/116Z/Z,0.008 856, f(Z/Z,)-7.786 7(Z/Z,)+16/116 Where: For the conditions specified in 5.1
X, =96. 422,Y, 100.00,Z, =82.521Cu =(a*2 +b*2)1/2
ha =tan-1(b\ /a\)
Where:
When a>0,b*≥0,0≤ha<90°
When a*≤0,b*>0,90≤ha<180°
When a\0,b*0,180°h270°
When a\≥0,6\<0,270≤h<360
B.2CIELUV chromaticity parameters (see C IE Publication 15.2) L*=116[f(Y/Y,)]-16
u*=13L*(u'—u')
*=13L('-n)
where:
u'=4X/(X+15Y+3Z)
=9Y/(X+15Y+3Z)
and u'n,, is the u', value of the reference white.
The two spaces defined above are both homogeneous color spaces. They are called homogeneous color spaces because they are much better than the XYZ color space in terms of numerical differences in expressing the same perceived color differences. Due to the needs of use, both color spaces were approved by CIE in 1976, one of which has a chromaticity diagram corresponding to the color space, and its coordinates must be linearly related to and. For users who study color mixing (including the television industry), the linearity of the XYZ system is an important feature. Since the color obtained by mixing color light can be easily predicted by the additive method, the color gamut formed by the mixture can be easily defined by constructing linear boundaries between the three primary colors and black and white. When defined by chromaticity coordinates, it can be simplified to a triangle composed of the coordinate values ​​of the three primary colors. Therefore, the chromaticity diagram composed of u and values ​​just meets the requirement that the uniform color space has a corresponding chromaticity diagram. Colorants cannot show the additive color process. Mediums with purer colors, such as dyes, can be well simulated when measured by color density. However, it is not widely used in the printing industry because pigments with turbidity characteristics are commonly used in printing reproduction. It is often said that CIELAB provides a more uniform space suitable for printing applications. Although it is rarely proven, it is accepted by the printing industry and widely cited. This color space is also preferred for this standard, however, since it has no linear relationship with XYZ (because α\ and 6 are cube roots in the calculation), there is no corresponding chromaticity diagram. Therefore, the color gamut of a set of additive primaries cannot be easily calculated. When strict accuracy is not required, due to the non-additive nature of the pigments, the color gamut of the pigments used for color reproduction is sometimes approximated by a hexagon in a u' diagram connecting the primary and secondary colors. This can be directly compared with the color gamuts obtained by other color systems and, more importantly, with the colors obtained by a color monitor (or any other additive color system). Obviously, such comparisons must be treated with caution, due to the non-additive nature of the pigments (and because such a chromaticity diagram cannot represent lightness or brightness). The above applications have demonstrated that CIELUV has a certain value in printing technology. B.3 CIELAB colour difference (see CIE publication 15.2) AL\ = L * —L *
Aa\ = a1* —a2
A6* = b * -- b2 *
AC = Ca1 —C2
Tha hab1 —— hab2
The ΔE obtained for L, a” and 6” in samples 1 and 2 is: E [(ΔL*)?+(Δa*)2+(*)?]1/2
CIE currently defines a metric colour difference ΔH: AH [(ΔE)?-(ΔL* )2-(AC)2]1/2 B.4 CMC (1:c) colour difference AEmc (see BS 6923 [5]) AEanc = [(AL* / ISL)*+(ΔC /cSc)2+(AH /SH)°1/2where:
△L", AC and △H are as defined in B.3; SL=0.040975L\/(1+0.01765L*), if L*<16, then St=0.511Sc=0.0638C/(1+0.0131C)+0.638#SH=Sc(FT+1-F)
where:
F= ((C)* /[(C± )4 +1900])1/2 ;T==0.36+10.4cos（ha+35)l; if 164≤ha≤345°, then T=0. 56+10. 2 cos (ha +168)/. NOTE 14: CMC (Colour Measurement Committee, a UK organisation) colour difference is not currently approved or recommended by CIE, but a modified version is being considered for incorporation into other colour difference formulas. The parameter values ​​in the
CMC equation are derived based on what is acceptable to the textile industry, rather than on perceptual visual judgement. When l = 2, the value of AEmc is consistent with the visual perception of colour difference in textiles. In current applications, the value of c is always equal to 1 and is given in the formula for consistency with British Standard BS 6923 [5] (see also AATCC Test Method 173-1990). Different colour difference tolerances may require other values ​​of 1 and c. However, for different surface colours even different relationships for SL, Sc, SH, F and T may be used. Different color difference tolerances may require different I and c values. The CMC color difference model helps to establish empirical tolerances. For color differences less than 3, the △E color difference formula is more advantageous. [See CIE Publication: 116--1995 (Formula 2.11)]. 9
GB/T19437-2004/IS013655:1996 Appendix C
(Informative Appendix)
Spectral weighting coefficients using D65 light source and 2° field of view observation conditions For the convenience of those who do not meet this standard but use the CIE standard illuminant Dss, the weighting coefficients for calculating the tristimulus values ​​using the CIE illuminant Ds and the CIE1931 standard colorimetric observer (commonly referred to as the 2° field of view) are listed here. X, 95.047, Y = 100.000 and Z, -108.833 can be used for chromaticity calculations. Note 15: In Table C.1 and Table C.2, the sum of the weighting coefficients from 340nm to 780nm is not equal to the values ​​of X, Y, and Z. This is because X, Y, and Z are calculated according to ASTM E308 and are more accurate than the values ​​given in the table. The sum of X, Y, and Z in the table can be used to verify the data in this table. Table C.1 Weighting coefficients for calculating tristimulus values ​​under D6s illuminant and 2° field of view observation conditions (interval 10 nm) Wavelength/nm
Both spaces defined above are uniform color spaces. They are called uniform color spaces because they are much better than XYZ color spaces in terms of numerical differences in representing the same perceived color difference. Due to the needs of their use, both color spaces were approved by CIE in 1976. One of them has a chromaticity diagram corresponding to the color space, and its coordinates must be linearly related to and. For users who study the mixing of light (including the television industry), the linearity of the XYZ system is an important feature. Since the additive method can easily predict the colors obtained by mixing light, the color gamut formed by the mixture can be easily defined by constructing linear boundaries between the three primary colors and black and white. When defined by chromaticity coordinates, it can be simplified to a triangle composed of the coordinate values ​​of the three primary colors. Therefore, the chromaticity diagram composed of u and values ​​just meets the requirement that the uniform color space has a corresponding chromaticity diagram. Colorants cannot show additive color processes. Mediums with pure colors, such as dyes, can be well simulated when measured by color density. However, it is not widely used in the printing industry because pigments with turbidity characteristics are commonly used in printing reproduction. It is often said that CIELAB provides a more uniform space suitable for printing applications, although this is rarely proven, it is accepted by the printing industry and is widely cited. This standard also tends to use this color space, however, because it has no linear relationship with XYZ (because α\ and 6 are cube roots in the calculation), there is no corresponding chromaticity diagram. Therefore, the color gamut of a set of additive primary colors cannot be easily calculated. When strict accuracy is not required, due to the non-additive nature of the pigment, a hexagon in the u' diagram connecting the three primary colors and the secondary colors is sometimes used to approximate the color gamut of the color reproduction pigment. This can be directly compared with the color gamut obtained by other color systems, and more importantly, it can be compared with the colors obtained by color monitors (or any other additive color system). Obviously, such comparisons must be treated with caution because of the non-additive nature of the pigments (and because such chromaticity diagrams cannot represent lightness or brightness). The applications described above demonstrate that CIELUV has value in printing technology. B.3 CIELAB colour difference (see CIE publication 15.2) AL\ = L * —L *
Aa\ = a1* —a2
A6* = b * -- b2 *
AC = Ca1 —C2
Tha hab1 —— hab2
The ΔE obtained for L, a” and 6” in samples 1 and 2 is: E [(ΔL*)?+(Δa*)2+(*)?]1/2
CIE currently defines a metric colour difference ΔH: AH [(ΔE)?-(ΔL* )2-(AC)2]1/2 B.4 CMC (1:c) colour difference AEmc (see BS 6923 [5]) AEanc = [(AL* / ISL)*+(ΔC /cSc)2+(AH /SH)°1/2where:
△L", AC and △H are as defined in B.3; SL=0.040975L\/(1+0.01765L*), if L*<16, then St=0.511Sc=0.0638C/(1+0.0131C)+0.638#SH=Sc(FT+1-F)
where:
F= ((C)* /[(C± )4 +1900])1/2 ;T==0.36+10.4cos（ha+35)l; if 164≤ha≤345°, then T=0. 56+10. 2 cos (ha +168)/. NOTE 14: CMC (Colour Measurement Committee, a UK organisation) colour difference is not currently approved or recommended by CIE, but a modified version is being considered for incorporation into other colour difference formulas. The parameter values ​​in the
CMC equation are derived based on what is acceptable to the textile industry, rather than on perceptual visual judgement. When l = 2, the value of AEmc is consistent with the visual perception of colour difference in textiles. In current applications, the value of c is always equal to 1 and is given in the formula for consistency with British Standard BS 6923 [5] (see also AATCC Test Method 173-1990). Different colour difference tolerances may require other values ​​of 1 and c. However, for different surface colours even different relationships for SL, Sc, SH, F and T may be used. Different color difference tolerances may require different I and c values. The CMC color difference model helps to establish empirical tolerances. For color differences less than 3, the △E color difference formula is more advantageous. [See CIE Publication: 116--1995 (Formula 2.11)]. 9
GB/T19437-2004/IS013655:1996 Appendix C
(Informative Appendix)
Spectral weighting coefficients using D65 light source and 2° field of view observation conditions For the convenience of those who do not meet this standard but use the CIE standard illuminant Dss, the weighting coefficients for calculating the tristimulus values ​​using the CIE illuminant Ds and the CIE1931 standard colorimetric observer (commonly referred to as the 2° field of view) are listed here. X, 95.047, Y = 100.000 and Z, -108.833 can be used for chromaticity calculations. Note 15: In Table C.1 and Table C.2, the sum of the weighting coefficients from 340nm to 780nm is not equal to the values ​​of X, Y, and Z. This is because X, Y, and Z are calculated according to ASTM E308 and are more accurate than the values ​​given in the table. The sum of X, Y, and Z in the table can be used to verify the data in this table. Table C.1 Weighting coefficients for calculating tristimulus values ​​under D6s illuminant and 2° field of view observation conditions (interval 10 nm) Wavelength/nmValues.
Both spaces defined above are uniform color spaces. They are called uniform color spaces because they are much better than XYZ color spaces in terms of numerical differences in representing the same perceived color difference. Due to the needs of their use, both color spaces were approved by CIE in 1976. One of them has a chromaticity diagram corresponding to the color space, and its coordinates must be linearly related to and. For users who study the mixing of light (including the television industry), the linearity of the XYZ system is an important feature. Since the additive method can easily predict the colors obtained by mixing light, the color gamut formed by the mixture can be easily defined by constructing linear boundaries between the three primary colors and black and white. When defined by chromaticity coordinates, it can be simplified to a triangle composed of the coordinate values ​​of the three primary colors. Therefore, the chromaticity diagram composed of u and values ​​just meets the requirement that the uniform color space has a corresponding chromaticity diagram. Colorants cannot show additive color processes. Mediums with pure colors, such as dyes, can be well simulated when measured by color density. However, it is not widely used in the printing industry because pigments with turbidity characteristics are commonly used in printing reproduction. It is often said that CIELAB provides a more uniform space suitable for printing applications, although this is rarely proven, it is accepted by the printing industry and is widely cited. This standard also tends to use this color space, however, because it has no linear relationship with XYZ (because α\ and 6 are cube roots in the calculation), there is no corresponding chromaticity diagram. Therefore, the color gamut of a set of additive primary colors cannot be easily calculated. When strict accuracy is not required, due to the non-additive nature of the pigment, a hexagon in the u' diagram connecting the three primary colors and the secondary colors is sometimes used to approximate the color gamut of the color reproduction pigment. This can be directly compared with the color gamut obtained by other color systems, and more importantly, it can be compared with the colors obtained by color monitors (or any other additive color system). Obviously, such comparisons must be treated with caution because of the non-additive nature of the pigments (and because such chromaticity diagrams cannot represent lightness or brightness). The applications described above demonstrate that CIELUV has value in printing technology. B.3 CIELAB colour difference (see CIE publication 15.2) AL\ = L * —L *
Aa\ = a1* —a2
A6* = b * -- b2 *
AC = Ca1 —C2
Tha hab1 —— hab2
The ΔE obtained for L, a” and 6” in samples 1 and 2 is: E [(ΔL*)?+(Δa*)2+(*)?]1/2
CIE currently defines a metric colour difference ΔH: AH [(ΔE)?-(ΔL* )2-(AC)2]1/2 B.4 CMC (1:c) colour difference AEmc (see BS 6923 [5]) AEanc = [(AL* / ISL)*+(ΔC /cSc)2+(AH /SH)°1/2where:
△L", AC and △H are as defined in B.3; SL=0.040975L\/(1+0.01765L*), if L*<16, then St=0.511Sc=0.0638C/(1+0.0131C)+0.638#SH=Sc(FT+1-F)
where:
F= ((C)* /[(C± )4 +1900])1/2 ;T==0.36+10.4cos（ha+35)l; if 164≤ha≤345°, then T=0. 56+10. 2 cos (ha +168)/. NOTE 14: CMC (Colour Measurement Committee, a UK organisation) colour difference is not currently approved or recommended by CIE, but a modified version is being considered for incorporation into other colour difference formulas. The parameter values ​​in the
CMC equation are derived based on what is acceptable to the textile industry, rather than on perceptual visual judgement. When l = 2, the value of AEmc is consistent with the visual perception of colour difference in textiles. In current applications, the value of c is always equal to 1 and is given in the formula for consistency with British Standard BS 6923 [5] (see also AATCC Test Method 173-1990). Different colour difference tolerances may require other values ​​of 1 and c. However, for different surface colours even different relationships for SL, Sc, SH, F and T may be used. Different color difference tolerances may require different I and c values. The CMC color difference model helps to establish empirical tolerances. For color differences less than 3, the △E color difference formula is more advantageous. [See CIE Publication: 116--1995 (Formula 2.11)]. 9
GB/T19437-2004/IS013655:1996 Appendix C
(Informative Appendix)
Spectral weighting coefficients using D65 light source and 2° field of view observation conditions For the convenience of those who do not meet this standard but use the CIE standard illuminant Dss, the weighting coefficients for calculating the tristimulus values ​​using the CIE illuminant Ds and the CIE1931 standard colorimetric observer (commonly referred to as the 2° field of view) are listed here. X, 95.047, Y = 100.000 and Z, -108.833 can be used for chromaticity calculations. Note 15: In Table C.1 and Table C.2, the sum of the weighting coefficients from 340nm to 780nm is not equal to the values ​​of X, Y, and Z. This is because X, Y, and Z are calculated according to ASTM E308 and are more accurate than the values ​​given in the table. The sum of X, Y, and Z in the table can be used to verify the data in this table. Table C.1 Weighting coefficients for calculating tristimulus values ​​under D6s illuminant and 2° field of view observation conditions (interval 10 nm) Wavelength/nm638#SH=Sc(FT+1-F)
Where:
F= ((C)* /[(C± )4 +1900])1/2; T==0.36+10.4cos(ha+35)l; If 164≤ha≤345°, then T=0.56+10.2cos(ha +168)/. NOTE 14: CMC (Colour Measurement Committee, a UK organisation) colour differences are not currently approved or recommended by CIE, but a revised version is under consideration for incorporation into other colour difference formulas. The parameter values ​​in the
CMC equation are based on what is acceptable to the textile industry, rather than on perceptual visual judgement. When l=2, the value of AEmc is consistent with the visual perception of colour difference in textiles. In current applications, the value of c is always equal to 1 and is given in the formula for consistency with British Standard BS6923[5] (see also AATCC Test Method 173-1990). Different color difference tolerances may require other values ​​of I and c. However, different surface colors and different color difference tolerances may require different values ​​of I and c, even with different SL, Sc, SH, F and T relationships. The CMC color difference model helps to establish empirical tolerances. For color differences less than 3, the △E color difference formula is more advantageous. [See CIE Publication: 116--1995 (Formula 2.11)]. 9
GB/T19437-2004/IS013655:1996 Appendix C
(Informative Appendix)
Spectral weighting coefficients using D65 light source and 2° field of view observation conditions For the convenience of those who do not comply with this standard but use the CIE standard illuminant Dss, the weighting coefficients for calculating the tristimulus values ​​using the CIE illuminant Ds and the CIE1931 standard colorimetric observer (commonly referred to as the 2° field of view) are listed here. X, 95.047, Y = 100.000 and Z, -108.833 can be used for chromaticity calculation. Note 15: In Table C.1 and Table C.2, the sum of the weighting coefficients from 340nm to 780nm is not equal to the values ​​of X, Y, and Z. This is because X, Y, and Z are calculated according to ASTME308 and are more accurate than the values ​​given in the table. The sum of X, Y, and Z in the table can be used for data verification of this table. Table C.1 Weighting coefficients for calculating tristimulus values ​​under D6s illuminant and 2° field of view observation conditions (interval 10 nm) Wavelength/nm638#SH=Sc(FT+1-F)
Where:
F= ((C)* /[(C± )4 +1900])1/2; T==0.36+10.4cos(ha+35)l; If 164≤ha≤345°, then T=0.56+10.2cos(ha +168)/. NOTE 14: CMC (Colour Measurement Committee, a UK organisation) colour differences are not currently approved or recommended by CIE, but a revised version is under consideration for incorporation into other colour difference formulas. The parameter values ​​in the
CMC equation are based on what is acceptable to the textile industry, rather than on perceptual visual judgement. When l=2, the value of AEmc is consistent with the visual perception of colour difference in textiles. In current applications, the value of c is always equal to 1 and is given in the formula for consistency with British Standard BS6923[5] (see also AATCC Test Method 173-1990). Different color difference tolerances may require other values ​​of I and c. However, different surface colors and different color difference tolerances may require different values ​​of I and c, even with different SL, Sc, SH, F and T relationships. The CMC color difference model helps to establish empirical tolerances. For color differences less than 3, the △E color difference formula is more advantageous. [See CIE Publication: 116--1995 (Formula 2.11)]. 9
GB/T19437-2004/IS013655:1996 Appendix C
(Informative Appendix)
Spectral weighting coefficients using D65 light source and 2° field of view observation conditions For the convenience of those who do not comply with this standard but use the CIE standard illuminant Dss, the weighting coefficients for calculating the tristimulus values ​​using the CIE illuminant Ds and the CIE1931 standard colorimetric observer (commonly referred to as the 2° field of view) are listed here. X, 95.047, Y = 100.000 and Z, -108.833 can be used for chromaticity calculation. Note 15: In Table C.1 and Table C.2, the sum of the weighting coefficients from 340nm to 780nm is not equal to the values ​​of X, Y, and Z. This is because X, Y, and Z are calculated according to ASTME308 and are more accurate than the values ​​given in the table. The sum of X, Y, and Z in the table can be used for data verification of this table. Table C.1 Weighting coefficients for calculating tristimulus values ​​under D6s illuminant and 2° field of view observation conditions (interval 10 nm) Wavelength/nm
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