Specification for optical densitometric measurements of printed maps
Some standard content:
National Standard of the People's Republic of China
Specification for optical densitometric measurements of printed maps1Subject content and scope of application
GB/T 15638---1995
This standard specifies the density measurement content and operating procedures of printed original maps, transitional negative/positive films, tear-off films, proofing samples and map prints in the map printing process.
This standard is applicable to the quality inspection of topographic maps, thematic maps and image map prints. It can be used as a reference for non-map prints. 2 Reference standards
GB2675 Map paper
Maritime paper
GB 2676
GB14051 Colors for topographic maps
GB14510 Specifications for image map printing
QB320 Coated paper for offset printing
3 General principles
3.1 Density measurement of map printing and its products is an important part of achieving standardization of map printing implementation: it is also an effective means to check and control the quality of map prints.
3.2 In order to ensure the printing quality of maps, density detection must be carried out on printed originals, transitional negative/positive films, tear-off films, proofing drawings and map prints.
3.3 Negative/positive films refer to various line strokes, symbols, dots/screen lines and text films obtained by photography, copying, tear-off or electronic color separation and screening processes.
3.4 Density measurement is completed using an optical densitometer and a measurement and control strip. Transparent originals and negative/positive films are tested with transmission densitometers, and friendly originals, proofs and printed images are tested with reflection densitometers. 3.5 Different types of optical densitometers will provide different density values. In order to implement the standardization of density measurement, the same type of optical densitometers produced by the same manufacturer should be selected. When the difference in the photoelectric characteristics of the optical densitometer is not greater than 0.3 in the field, the mathematical method of regression analysis can be used to establish the conversion equation between different optical density evaluation readings to enhance its versatility. See Appendix (. 4 Basic requirements for optical densitometers
4.1 In order to measure the control strip, the diameter of the optical densitometer's measuring hole should not be greater than 4mm4.2 The measurement range of transmission density should be 0.00~4.00, and the measurement range of reflection density should be 0.00~2.50. 4.3 The measurement accuracy of the optical densitometer should be less than ±0.02. The error of repeated measurements should be less than ±0.014.4 The measurement range of the optical coverage of the dot area should be 0~100%. 4.5 The optical densitometer should be accompanied by a standard black and white test plate and a gray scale to facilitate the calibration of the optical densitometer. Approved by the State Administration of Technical Supervision on July 24, 1995456
Implementation on January 1, 1996
GB/T 15638--1995
4.6 High-precision optical densitometers should have grounding devices to prevent leakage. 4.7 Due to light source exposure and natural aging, the filters of the color densitometer should be calibrated or replaced regularly with standard color plates. 4.8 The use of the light source for a transmission densitometer should not exceed: 1000h, and the use of the light source for a reflection densitometer should not exceed 3000h. 4.9 In order to eliminate the difference in density measurement caused by different wet states under the oil, a reflection densitometer with a polarizing filter device should be used.
5 Working environment of optical densitometer
5.1 The optical densitometer should be placed away from heat sources, and the ambient temperature should be between 10° and ~10C. 5.2 To maintain air circulation around the optical densitometer, the relative humidity should be controlled between 0 and 80%. 5.3 The power supply voltage should meet the use requirements of the optical densitometer, and the Normally 220V ± 10%. 5.4 Prevent the optical densitometer from being irradiated directly by strong light. There must not be any corrosive gas or strong electromagnetic field interference to avoid reducing the measurement accuracy. 6 Preparation before density measurement
6.1 Place the optical densitometer on a flat and clean workbench. 6.2 Wipe the outer shell and light hole of the optical densitometer with a soft cloth dipped in detergent to keep it clean. 6.3 Carefully wipe the standard black and white test board and gray scale. 6.4 Pay attention to the safety and reliability of the circuit. Only turn on the power supply after confirming that the power supply voltage matches the working voltage of the optical densitometer. 7 Density measurement procedure
7.1 Calibration of the optical densitometer
In order to ensure the accuracy of density measurement, the optical densitometer must be calibrated before formal measurement. 7.1.1 Calibration of transmission densitometer
a. Turn on the power and preheat for 10 min;
b. Set the transmission density of the four channels (red, green, blue, and white) to zero respectively; c. Regularly use the fine-tuning knob of the optical densitometer to test the transmission density of the four filters according to the calibration value of the gray scale, so that the actual reading value coincides with the calibration value of the gray scale, and the allowable error is ±0.01; d. Remove the gray scale and store it carefully for next use. 7.1.2 Calibration of reflection densitometer
Turn on the power supply and preheat for 10 minutes;
b. Wipe the standard black and white test plate with a soft cloth; Use the "buttocks" knob to set the reflection density of the red, green, blue, and white filters to zero; c.
d. Place the standard black test plate under the red, green, blue, and white test heads in turn, and use the fine-tuning knob to make the reflection density value coincide with the calibration value on the standard black test plate, and the allowable error is ±0.01; e. Remove the standard black and white test plate for next use. 7.2 Transmission density measurement procedure
7.2.1 In order to eliminate the gray fog of the transmission film, the measuring heads of the four filters need to be aligned with the non-image area of the film before measurement. 7.2.2 Place the dried black and white or color negative/positive film on the measuring table of the optical densitometer. 7.2.3 According to the principle of color complementation, refer to Table 1 to select the test head and measure the reading. 4.37
Measured color
3---1995
GB/T 15638
Filter
Kodak Raiden 47B
Kodak Raiden 58
Kodak Raiden 25
Kodak Raiden 106
Kodak Raiden 94
Kodak Raiden 93
Kodak Raiden 92
7.3 Procedure for Reflection Density Measurement
Filter Color
For Reflection Densitometer
For Reflection Densitometer Densitometer
For reflection densitometer
For reflection or transmission densitometer
For transmission densitometer
For transmission densitometer
For transmission densitometer
7.3.1 Place the sample to be measured on the measuring table. If the sample to be measured has a picture on one side, white paper should be placed on the back to prevent the influence of uneven paper transmittance; if the sample to be measured has pictures on both sides, black paper should be placed on the back to prevent the influence of the back picture. When measuring, the measured part should be selected in the part without folding, fingerprints, scratches, etc. of the film/paper. 7.3.2
Set to zero.
To eliminate the influence of different papers on the reflection density, select the filter by referring to Table 1 for the reflection density of the non-picture part of the measured paper before formal measurement, press the probe and record the reading. 7.3.4
7.3.5 Repeat the measurement 2 to 3 times. When the density value is below 1.0, the error should be controlled within 0.01, and when it is above 1.0, it can be controlled within 0.02. If it exceeds the allowable range, the density meter should be repaired. 7.3.6 When the optical density meter is used continuously, the power supply cannot be turned off. Density measurement of printed original images
8.1 Density measurement of line-stroke original images
8.1.1 Density requirements for line-stroke original images
For engraved original images, the density of the engraved film layer should meet the following requirements: the density of the yellow engraved film is greater than 0.6, the green engraved film is greater than 1.3, the orange-red white engraved film is greater than 1.5, and the gray fog of the light-transmitting part should be less than 0.1; b.
The optical density of the graphic part of the polyester film original image should be greater than 3.0; the optical reflection density of the graphic part of the mounted and cleared original image should be greater than 2.5. 8.1.2 Use the color filter of the transmission densitometer to detect the density of the engraved film to confirm whether it meets the requirements of 8.1.1.a. 8.2 Density measurement of continuous tone original image
8.2.1 For the density requirements of continuous tone original image, see Table 2Table 2
Black and white transmission continuous tone original image
Color transmission continuous tone original image
Black and white reflection continuous tone original image
Color reflection continuous tone original image
Gray fog
Minimum density
Maximum density
1. 6~1. 9
2.0～2.5
1. 3~~1. 4
1. 6-~1. 9
GB/T15638—1995
8.2.2 Use a transmission densitometer to detect the gray fog, minimum density, maximum density and density contrast of the black and white or color transmission continuous tone original image, and judge whether the original image meets the requirements of Table 2 of this specification. 8.2.3 Use a reflection densitometer to detect the gray fog, minimum density and maximum density of the black and white or color reflection continuous tone original image, and judge whether the original image meets the requirements of Table 2.
9 Density measurement of negative/positive film
9.1 Quality requirements for line-marked negative/positive film a. The line-marked negative/positive film is transparent and smooth, without sand holes;
b. The solid density of the negative/positive film should be greater than 3.0, and the gray fog should be less than 0.1. 9.2 Quality requirements for halftone negative/positive film a. The dots are smooth and solid;
b. The solid density of negative/positive film should be greater than 3.0, and the gray fog should be less than 0.1; C.
The dot ratio is accurate, and the error is less than ±2% in the 50% area rate section of the control strip. 9.3 Use a transmission densitometer to test the solid density, gray fog and dot ratio of the line-drawn negative/positive film and the screen-adjusted negative/positive film to confirm whether they meet the requirements of 9.1 and 9.2 of this specification. 10 Density measurement of tear-off film
10.1 Quality requirements for negative-positive tear-off film a. The film layer is firmly bonded, the dyeing is evenly drawn, there is no sand hole, and the transparent part has no gray fog; b. The density of negative-positive tear-off film should be greater than 2.5, and the gray fog should be less than 0.1, 10.2 Quality requirements for positive-positive tear-off film a. The color is evenly drawn, there is no sand hole, after exposure and development, the pattern is reproduced completely, and the transparent part has no gray fog; b. The density of positive-positive tear-off film should be greater than 2.5, and the gray fog should be less than 0.1. 10.3 Use a transmission densitometer to test the density and gray fog of negative-positive/positive-positive tear-off film to determine whether it meets the requirements of 10.1 and 10.2 of this specification.
11 Density measurement of dot/screen film and symbol film 11.1 Dot/screen film and symbol film are important tools for making map coloring, and have a great impact on the apparent quality of the map. Before use, they must be strictly measured for density. 11.2 Quality requirements for dot/screen film a. The outline of the dot/screen is clear;
b. The solid density of the dot/screen film should be greater than 4.0, and the gray fog should be less than 0.05; c. The dot ratio is accurate, and the error should be less than 1%. 11.3 Quality requirements for symbol film
a. The symbol is clear and the outline is clear;
b. The solid density of the symbol film should be greater than 4.0, and the gray fog should be less than (0.05. 11.4 Use a transmission density meter to measure the solid density and gray fog of the dot/screen film and the symbol film to determine whether they meet the requirements of 11.2 and 11.3.
11.5 According to the density of the dot/screen film, its dot/screen ratio can be calculated to determine whether the dot/screen ratio is uniform, see Appendix A.
12 Density measurement of set screen positive film
12.1 Quality requirements for set screen positive film
GB/T 15638
The solid density should be greater than 3.0, and the gray fog should be less than 0.1; 1995
The dots/screen lines are clear and the ratio is accurate. In the 50% area rate section of the control strip, the error should be less than ±2%. b.
12.2 Use a transmission density meter to measure the maximum density, gray fog and dot/screen line ratio of the screen positive film to determine whether it meets the requirements of 12.1. 13 Density measurement of proof drawing
13.1 Measurement content
Printing contrast;||tt ||Best solid density;
Dot gain value;
Oil porridge overprint rate. See Appendix B.
13.2 Quality requirements for proofing drawings
The paper used for proofing drawings shall comply with the technical regulations of GB2675, GB2676, QB320 and other standards; the ink used for proofing drawings shall comply with the following regulations: (0°/45° geometry, Ds5 light source)
M.ODE*(ab)
5.ODF*(ab)
3. ODE (ab)
1*=<18. 0
The printing contrast should be controlled within the following range (on coated paper): yellow 0.35±0.02, magenta 0.40±0.02, cyan 0.40±0.02, black 0.45±0.02;
The optimal solid density of the four-color standard printing ink should be controlled within the following range: yellow 1.05±0.05, magenta 1.35±0.05, cyan 1.45±0.05, black 1.60±0.05;
The dot gain value of the four-color printing ink on coated paper (at the 40% or 50% area rate of the measurement and control strip) should not exceed 15%; e.
f. The overprint rate of the standard three primary colors (yellow, magenta, cyan) should be controlled within the range of 100%±20%. 13.3 The density measurement procedure for the proof drawing is shown in this document. 7.3 of the specification. 14 Density measurement of printed images
14.1 The quality requirements for printed images are shown in 13.2 of this specification. 14.2 During printing, the density values of the ground and dot parts should be randomly sampled and measured. 14.3 The content and method of density detection of map prints are the same as those of proofing images. 460
Dot ratio calculation formula
Where: D—transmission density;
transmittance;
O—light blocking rate;
—dot ratio.
A2 Calculation example
GB/T15638—1995
Calculating dot ratio using density of dot film (supplement)
A2.1 Assume that D=0.4 of a dot film, calculate its dot ratio. According to formula (A2) and (A3), we can get: O-100.4 2.51;
60%.
2If the percentage of the halftone film is known, its transmission density can also be inversely calculated. The calculation formula is as follows: A2.2
n= lgo
(A1))
(A2)
(A4)
·(A5)
Assuming that the percentage of a certain halftone film is known to be α=60%, according to formula (A4) and (A5), we can get: O2.5, D1g2.50.4. Appendix B
Ink overprint rate
(supplement)
B1 Overprint rate
In order to implement the standardization of map printing, the printing color sequence of the oil must be determined. The ink overprint rate reflects the acceptance of the ink porridge printed on the paper first to the ink purple printed later.
2 Ink overprint rate (T) calculation formulaWww.bzxZ.net
Wherein D.2—solid density of the first color;
D)—solid density of the first color;
D,——solid density of the second color.
GB/T 15638-1995
Di.2 + D,
When measuring D, D, and D.2, the complementary color filter of D. is used. B3 Calculation example
×100%
Assume that the first color is cyan (C) and the second color is magenta (M). According to the subtractive color mixing principle of colorants, the overprinted intermediate color is blue (B). The solid density (1) of the first ink measured with a green filter is 0.14, the solid density (Dm) of the second ink is 1.45, and the solid density (D) of blue is 1.49. The overprint rate of magenta ink (7sm) = (D + D) - Dm × 100% = 112%. Appendix C
Regression analysis and equation between optical densitometer readings (reference)
C1 Calculation of regression parameters
Research experiments have shown that there is a good linear correlation between optical densitometer readings with little difference in photoelectric characteristics. According to regression analysis theory, if n variable groups (X,, Y) (i1,2.) fall near a certain straight line, it can be assumed that the regression equation is a straight line, which is expressed as follows:
Where: a
The intercept of the regression line;
The regression coefficient.
For any straight line on the plane, its predicted value y, -α+b·α (=1, 2, 3.n) can be calculated. The calculation formula of linear regression is as follows:
(r, -y) -
nr -(r,)
In regression analysis, the critical value of the correlation coefficient (r) is calculated by the following formula:n.(α y,)-
Sx·Xy
V.(a)n.-(y)
·(C3 )
GB/T15638--1995
From the formula, we know that ≤1. When the value is close to 1, it means that, and y are well correlated; when the value approaches zero, it means that and rent are poorly correlated. A and always have the same positive or negative sign. The measured value has a certain randomness, and the calculated value is a statistic, and its reliability must be tested by statistical hypothesis. The method is as follows:
Assume that α, and y,It is not recommended to use linear correlation. The statistic t should follow a distribution with (n2) degrees of freedom. t = -
For a given value of a, its critical value ta can be found from the t distribution critical value t table (see Table C1), and then the r. value can be solved using the function of ra related to t.
If r, that is, the hypothesis is established, it means that there is no linear correlation between and; if ≥r, it means that there is a linear correlation between and. To determine the r. value, see the distribution critical value ta table in Table C1. Table C1
Degrees of freedom r
Test the critical value of the correlation coefficient P-0, see Table C2. Degree of freedom r
α: 0. 05
f=n -2
Example of calculation of regression equation
GB/T 15638—1995
0.999 877
0.990.000
In order to establish the regression equation between the readings of Macbeth RD-511 (as a comparison standard) optical densitometer and Gretag D-142 and Macbeth 918 optical densitometers, 27 magenta coated paper samples were measured using the above three optical densitometers. The measured density data are shown in Table C3.
Densitometer
Sample number
Magenta: 1
Sample number
Densitometer M-514
GB/T15638
—1995
C2.2 Using formula (C2), (C3), (C4) and Table C2, the regression i calculation of the relevant data in Table C3 can be used to calculate the a, h, r and r values of (retag)-142 and Macbeth 918 optical densitometers corresponding to Macbeth RD-514, see Table C4. Table C4
Measured data
Optical densitometer
MacbethRD-514
Gretag.D-142
Macbeth.918
As standard
Good correlation
Good correlation
C2.3 From the data in Table C4, we can see that ≥r., indicating that there is a linear correlation between the readings of the three optical densitometers, and because the [r| value approaches 1, it shows that there is a good linear correlation between the readings of the three optical densitometers. C2.4 Using the α and b values in Table C4, the regression equations between Macbeth RD-514 optical densitometer and Gretag D142 and Macbeth-918 can be written:
The regression equation between M-514 and G, D-142 is: y, -0.332 + 1.330x; the regression equation between M-514 and M-918 is: 3 = -0.192 + 1.266rAdditional remarks:
This standard was proposed and assigned by the State Administration of Surveying, Mapping and Geoinformation. The Chinese Academy of Surveying and Mapping and the Institute of Surveying and Mapping Standardization of the State Administration of Surveying, Mapping and Geoinformation were responsible for drafting this standard. The drafters of this standard were Zhang Qingpu, Wei Ruiqin and An Zhenzhen. 165
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