JP2005153289A - Control method of offset printing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a controlled density value and an allowable fluctuating range necessary for realizing the color reproduction near to standard printing colors given by colorimetric values and further more necessary correction after consideration to unstability in printing and dry-down. <P>SOLUTION: The necessary controlled density value, allowable fluctuating range and correction are obtained by non-linearly regression-analyzing the correlation between the color difference value from standard color and solid density, which is obtained by repeating the measurements of the density values before dry-down and of the colorimetric values after dry-down of step wedge images at printing work. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an offset printing management method, and more particularly to a management method for uniquely obtaining a management density value and an allowable range necessary to approximate reference color reproduction.

  In the printing work, numerical management using a measuring instrument is required so that reproduction as intended by the creator can be obtained on the reflective media. Such a numerical value is called a “management parameter”, and an image having a gradation value of a specific halftone dot area ratio is usually defined as a “management patch”, and an actually measured value of the management patch print result is set as a target. Management is realized by adjusting the printing conditions so as to approach a given “management value”.

  In offset printing, management using optical reflection density values (hereinafter referred to as density values) is mainly performed. In particular, a solid density, that is, a density value of a solid image in which a primary color having a halftone dot area ratio of 100% is used as a management patch is used as a management parameter. Solid density management values, that is, management density values, are based on the use of standard printing plates, inks, and paper, and are available in colors such as indigo, red, yellow, and black from printer manufacturers and organizations that provide standard printed materials. It is generally presented for each ink type. The printing operator controls the ink feed amount by adjusting the rotation amount of the ink source roller of the printing press and the opening of the ink key for each area divided in the width direction, and the density value of the management patch at the time of printing. Work to get closer to the control value.

  In offset printing, a halftone dot area ratio (hereinafter referred to as an actually measured halftone percentage) calculated using the Malay Davis equation from the density value of a patch image having a specific halftone dot area ratio on data is also used for halftone images. It is widely used as a management parameter for confirming tone reproduction. As a management parameter for halftone image reproduction calculated from the density value, a dot gain amount obtained by taking the difference between the measured halftone percentage and the halftone dot area ratio on the data is also used. Call it. Generally, the management value of the dot gain amount is also presented by a printing press manufacturer or an organization that provides standard printed matter. The printing operator controls the ink feed amount so that the dot gain amount approaches the control value.

  Note that the solid density value and the dot gain amount cannot always be adjusted to the management value at the same time. In such a case, it is determined that the plate making conditions or the printing conditions are not compatible with the standard printing, and the plate making conditions or the printing conditions are corrected.

  In recent years, in addition to management parameters using such density values, “colorimetric values” that objectively describe colors with three variables, such as CIELAB, have come to be used as management parameters. For example, in the ISO12647-2 standard, the colorimetric values of the solid image of the paper and the primary color and the secondary color are set for each of several types of offset printing conditions, and in the Japan Color 2001 standard printing color, the ISO12642 is set for each of several types of offset printing conditions. The colorimetric values of the 928 color patches defined in the above are presented as a standard.

  Recently, with the widespread use of color devices, it has become necessary to specify the color reproduction of offset printing, so the importance of specifying the standard color reproduction of offset prints by colorimetric values has increased. Yes.

  In actual printing operations, only the ink feed amount can be controlled, so that the colorimetric values for displaying colors with three variables tend to be somewhat difficult for the operator. Therefore, printing management using colorimetric values is generally performed using a system having a program developed exclusively for the color measurement.

  Since such a dedicated management system is expensive, for many printing operators, the standard color given by the colorimetric value is the standard density value, the standard dot gain amount, and their allowable variation range. It is desirable to express it with the management parameters that have been used.

  However, as pointed out in Non-Patent Document 1, even if the colorimetric values are the same, the density value differs depending on the spectral absorption characteristics of the color ink used and the emulsified state during printing. It is also known that the reflection density value varies depending on the standard of the filter employed, such as ANSI-T, DIN, and DIN-NB, depending on the type of reflection densitometer. For this reason, in the Japan Color 2001 standard printing color and ISO12647-2, it is recommended that the printing operator determine the management density value as a reference by himself / herself.

  However, in print management, it is necessary to use the measurement value immediately after printing, but it is known that color reproduction fluctuates during a period of about 1 hour to 1 day after printing. Such a phenomenon is called dry-down, and measured values after dry-down are used when determining a standard print color. Therefore, it is difficult to determine the management density value.

In addition, when the chart image is actually printed with management patches and the management conditions are found to approximate the standard print reproduction, the print reproduction is unstable. It is necessary to handle it while considering the influence, and it is difficult to find a standard value uniquely. In particular, regarding the dot gain amount, there is a problem that it is difficult to grasp whether it is an error due to subtle flare that has occurred during printing or whether it is significantly different from the standard printing color due to the characteristics of the plate making or printing conditions. For this reason, even if the standard printing conditions are defined numerically, the management conditions at each printing site are often determined empirically by skilled workers.
Offset Sheet-fed Printing Color Standard JapanColor Color Reproduction 2001 Manual, ISO / TC130 National Committee, 2001, 2nd page

  The present invention has been made to address the problems of the conventional print management method described above, and its purpose is to consider conditions such as instability of printing, dry-down phenomenon, difference in filter standards of densitometer, etc. It is an object of the present invention to provide a print management method for obtaining a management density value and an allowable variation range necessary for realizing color reproduction close to a standard print color given by a colorimetric value in a certain procedure.

  The present invention further objectively presents the fact that if the standard printing color is difficult to reproduce due to the characteristics of the plate making conditions or printing conditions, the plate making conditions or printing conditions are not appropriate for the standard printing colors, It is another object of the present invention to provide a print management method that suggests corrections necessary to realize color reproduction close to the standard print color.

  As a result of intensive studies in view of the above, the present inventors have invented the following print management method.

  The print management method according to the first aspect of the invention is to measure a density value before dry-down during a printing operation and a colorimetric value after dry-down for a patch image for print management, and from the measured colorimetric values. A color difference from a target standard color is obtained, and a management density value and an allowable variation range at the time of printing are obtained from nonlinear regression analysis of a correlation between the density value and the color difference value.

  According to a second aspect of the present invention, there is provided a print management method for a step wedge image having a plurality of patch images having different dot area ratios arranged in an area managed by the same ink key of a printing press. The density value before drydown and the colorimetric value after drydown are measured, and the color difference from the target standard color is obtained for each patch from the measured colorimetric value. The density value of a specific patch image and each patch A management density value and an allowable variation range at the time of printing are obtained from nonlinear regression analysis of the correlation between the color difference values of the image.

  According to a second aspect of the present invention, there is provided a printing management method for printing a step wedge image having a plurality of patch images with different halftone dot area ratios arranged in an area managed by the same ink key of a printing press. Measure the density value before dry-down at the time and the colorimetric value after dry-down, obtain the color difference from the target standard color from the measured colorimetric value for each patch, An appropriateness of the plate making condition or the printing condition is determined from the nonlinear regression analysis of the correlation between the color difference values of each patch image.

  According to a third aspect of the present invention, there is provided a printing management method for a step wedge image having a plurality of patch images having different halftone dot area ratios arranged in an area managed by the same ink key of a printing press. Measures the density value before drydown and the density value after drydown, calculates the dot gain amount from the actually measured density value, and linearizes the correlation between the density value of a specific patch image and the dot gain amount of each patch image The tone correction amount of the output image is calculated from the regression analysis.

  In the above invention, a plurality of management patch images or step wedge images are arranged and measured in image areas managed by different ink keys of a printing press.

  According to the present invention, it is possible to provide a print management method for uniquely obtaining a management density value and an allowable variation range necessary for realizing color reproduction close to a standard print color given by a colorimetric value.

  Hereinafter, the present invention will be described through an operation procedure shown in FIG. 1 which is an embodiment of the present invention. The work procedure shown in FIG. 1 is an embodiment for carrying out all the inventions described in the claims, but is not restricted to this embodiment in carrying out the present invention.

  When performing print management according to the present invention, first select one of the standard print colors that are publicly available, or a standard printed product within the company, and measure the primary colors of indigo, red, yellow, and black. Record the value (ST01). Usually, the colorimetric values of the primary color are released by the organization that created the standard color, but if there is a standard color print sample, it is used by the operator to eliminate the influence of individual differences in colorimetric equipment. It is desirable to use the value measured by the instrument. Even if there are no published numerical values or print samples, if there is a standard print color ICC profile, you can know the required colorimetric values using commercially available image processing software for CMS.

  When selecting a standard print color, the allowable color difference value range is also determined. The color difference values are defined in the form of Equation 1 when the two colors are expressed as (L1, a1, b1) and (L2, a2, b2), respectively, as CIELAB values. Some printing standards, such as ISO12647-2, specify an allowable color difference value for each color ink, but can be determined according to the quality requirement level of the printing operator. In general, a color difference of 3 or less is a standard for strict management conditions, and 6 or less is a guide for mild conditions. Further, instead of the normal color difference value, a color difference value having higher correlation with human vision such as CMC color difference or CIE94 color difference can be used.

  Next, the media used for printing, that is, the types of ink and paper are selected (ST02). Normally, media that are appropriate for determining the standard print color are defined, and standard print colors that can be handled by the media manufacturer are publicly available. However, when a standard color or medium without such information is used, it is determined whether the medium is appropriate according to the second invention of the present invention described later.

  Next, plate making conditions and printing conditions for the printing plate are set (ST03). That is, basic printing management items such as press plate output calibration, exposure amount, printing press roller pressure and printing pressure, and blanket type are set. Normally, the conditions are set so that the worker can perform the daily work and the maintenance work most easily, but the work based on the present invention may determine that the plate making or printing conditions are inappropriate. Change the printing conditions.

  Next, a test chart image in which necessary management patch images are arranged is prepared (ST04). In the embodiment according to the first invention, a solid patch image for each color ink used as a test chart image is used. In the second and third embodiments, a step wedge image 20 comprising one or more halftone patch images 19A, 19B, 19C and a solid patch image 18 as shown in FIG. 2 is prepared for each color ink.

  One or more management patch images or step wedge images may be present in the test chart. However, as shown in FIG. 3, each of the regions 22 a to 22 f managed on the test chart image 21 with the ink key of the printing press. A plurality of step wedge images 23a to 23f can also be arranged. In such an embodiment, by controlling the opening degree of the ink key or the image area ratio of the dummy image 24 arranged other than the step wedge image, it is possible to obtain various solid density value data from one print sample. There are advantages. In the print management according to the present invention, since a large number of measurements are required, it is preferable to arrange the step wedge images in consideration of the workability of the measurement, such as using a scanning measuring instrument.

  When a test chart image is produced, it is output to a plate-making film, and then a printing plate is created by printing on the printing plate or direct output onto the printing plate by a CTP setter. In the present invention, the plate making method is not particularly limited, but it is required to record and confirm general plate making management items such as the data processing method at the time of printing, the degree of printing on the printing plate, the temperature of the developer, and the like.

  Next, after printing under the conditions set in ST03, the density of the patch image of the printed matter is measured and recorded (ST05). A solid patch is sufficient as a patch to be measured, but is not limited to a solid patch. It should be noted that the density measurement during the printing operation needs to be performed under the same conditions as in daily management. That is, the printing result is sampled during the work, and the density is measured with the same equipment as that used daily without being dried down. In order to obtain a highly reliable result in the present invention, it is desirable to obtain samples with various concentration values. Therefore, sampling is performed after changing the ink feed amount of the entire printing press, and step wedge images having various density values are obtained on the same print sample by using the above-described aspect in which a plurality of step wedges are arranged. Like that.

  Next, after waiting for the printed material to dry down, the colorimetric values of the patch image or step wedge image of the test chart sampled in ST05 are measured and recorded (ST06). It is known that the time required for dry-down is at least 2 hours or more, generally one day, and about two days depending on the type of media, and can be determined with reference to past cases. Then, a color difference value from the target standard print color is calculated from the actually measured colorimetric values. The correlation between the density value recorded in ST05 and the color difference value obtained in ST06 is indigo. Regression analysis is performed for each of the red, yellow, and black inks according to the following procedure.

  First, an embodiment of the first invention will be described with reference to FIG. FIG. 4 is a scatter diagram 1 in which the density value is taken on the X axis 2 and the color difference value is taken on the Y axis 3. The solid density value recorded in ST05 is X, and the color difference from the standard color of the solid image obtained in ST06. The actual measurement result 4 is plotted with square marks, where Y is the value. Even if the measured density value is larger than the control density value, or conversely smaller, the deviation from the standard color, that is, the color difference value becomes larger. Distributed in a convex shape.

  By performing nonlinear regression analysis on such a distribution, the correlation curve 5 of the color difference value distribution of the solid image as shown by the solid line can be derived. Although there are various methods for nonlinear regression analysis, it is possible to use a relatively simple 2nd to 4th order polynomial approximation by the least square method. From this correlation curve, it is possible to uniquely determine the management parameter in consideration of the influence of the dry-down phenomenon, the difference in the type of densitometer, the flare during printing, and the like. That is, the management density value 8 can be obtained from the point where the color difference value of the solid image is minimized, and the allowable fluctuation range 9 can be obtained from the range where the correlation curve falls below the allowable value of color difference determined in ST01 (ST07). FIG. 4 shows an allowable variation range when the color difference value 3.0 is an allowable value.

  In addition, there is a possibility that the minimum color difference value of the correlation curve 5 exceeds the allowable value of the color difference and the allowable range does not exist (C01 in FIG. 1). In such a case, it is checked whether there is a possibility that troubles such as over-emulsification and paper dusting have occurred during printing. If there is no problem in the printing conditions, it can be determined that the color reproduction of the ink used for printing does not conform to the target standard printing, so the process returns to ST02 and ink is selected again.

  Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 5 is a scatter diagram similar to FIG. 4. In addition to FIG. 4, the solid density value of the step wedge image recorded in ST05 is X, and the standard of the 50% mesh image in the same step wedge image obtained in ST06 is shown in FIG. A schematic actual measurement result 6 is plotted with US marks, where Y is the color difference value from the color.

  The measurement result 6 of the halftone image is also distributed in a downwardly convex shape in principle. Accordingly, similarly to the color difference distribution of the solid image, the correlation curve 7 of the color difference value distribution of the 50% halftone image can be derived by nonlinear regression analysis. In FIG. 5, only the 50% halftone patch is plotted as the halftone patch image for the sake of explanation, but the same plot can be made for the other halftone dot patches constituting the step wedge image. .

  By using a correlation curve for these halftone images, a range in which the color difference value falls below the allowable value determined in ST01, that is, an allowable density range is obtained. A range where the allowable density ranges of the halftone image and the solid image overlap can be given as the allowable variation range 10 in consideration of halftone reproduction. In addition, the median value of the allowable variation range can be given as the management density value. Also, since it is generally known that halftone images tend to recognize color shifts more easily than solid images, the color difference tolerance is flexible, such as using different values for solid images and halftones. Operation is also possible.

  In such a management method, as shown in FIG. 6, if the correlation curve 5 of the solid image and the correlation curve 7 of the halftone image are large and the allowable color difference value is 3.0, the allowable density range May not exist (C02 in FIG. 1). In such a case, in order to reproduce the target standard printing color with the determined accuracy, it is determined that the plate making condition or the printing condition is not appropriate, and the process returns to ST03 to correct the condition.

  As the correction of the plate making conditions, there are adjustments of the exposure amount when the analog plate is closely exposed and the beam intensity when the digital plate is scanned and exposed. Further, correction of printing conditions includes adjustment of the tack value of ink to be used, the type of blanket, printing pressure, roller pressure, dampening water composition and feed amount, and the like.

  However, recently, with the progress of digitization of the plate making process, tone reproduction can be numerically controlled when outputting a manuscript film or a plate. For this reason, it is more preferable that the exposure conditions and printing conditions of the printing plate are optimized for each device, and the correction work to approximate standard printing is performed by tone correction at the time of document film or printing plate output. For this purpose, an operation of calculating a tone correction amount (ST08A in FIG. 1) for approximating the standard printing is required. The third embodiment of the present invention relates to a method for calculating the correction amount.

  Next, a third embodiment of the present invention will be described. In the embodiment of the present invention, in the step of measuring and recording the colorimetric value of the step wedge image (ST06), the density value is also measured at the same time, and the dot gain amount is calculated from the density value and recorded. Then, the correlation between the density value before dry-down and the dot gain amount is examined in the form as shown in FIG.

  FIG. 7 is a scatter diagram 11 in which the density value is taken on the X-axis 2 and the dot gain amount is taken on the Y-axis 12. The solid density value before dry-down recorded in ST05 is X and the specific gradation obtained in ST06. In the halftone patch image having a value, Y is the dot gain amount, and the actual measurement result 13 is plotted with a mark of the US mark. In offset printing, the amount of dot gain tends to increase as the density value increases, so in principle the actual measurement results are distributed in a shape that rises to the right.

  When linear regression analysis is performed on such a distribution, the correlation between the solid image and the dot gain amount can be derived by a straight line 13 as indicated by a dotted line. From this straight line, a difference amount 17 between the estimated value 16 of the dot gain amount at the management density value 15 obtained by the above invention and the standard value 14 of the dot gain amount given by the standard printing is obtained. This difference amount 17 can be used as the tone correction amount for the specific gradation value described above in consideration of fluctuations during printing and the dry-down effect. That is, when the original film or printing plate is output, the dot gain amount of the final printing result is changed to the printing condition by performing the primary conversion so that the specific gradation value becomes a gradation value that is smaller by the difference amount 17. It is possible to approach the dot gain amount of standard printing without adding.

  For the sake of explanation, only the dot gain amount of one halftone dot is shown in FIG. 4, but the same processing is performed on a plurality of gradation value images constituting the step wedge image, and correction is performed for the entire tone reproduction. A value can also be obtained.

  In order to evaluate the effect of the present invention, according to the work procedure described in FIG. 5, the calculation of the standard solid density value based on the first invention, the determination of the appropriateness of halftone image reproduction based on the second invention, and Further, the correction based on the third invention was calculated, and compared with the conventional management method, the approximation effect on the standard printing was confirmed.

  As the target standard printing color, the Japan Color 2001 standard color was selected, and the colorimetric values and standard dot gain amounts of each primary color described in the manual were recorded (ST01). In addition, as a permissible color difference, Japan Color 2001 shows a numerical value that ΔE is within 6 as a minimum management item, but ΔE is targeted to be within 3 for the purpose of selecting more strict management conditions. did.

  Next, as media, DIC ValiusG and Mitsubishi Paper Pearl Coat, which are inks and papers clearly compliant with Japan Color, were selected (ST02).

  Then, plate making / printing conditions were set (ST03). That is, Mitsubishi SDP-αV was used as the printing plate and AGFA Galileo was used as the output machine, and the output conditions recommended by these manufacturers were selected. Also, Mitsubishi Heavy Industries DAIYA-3H was used for the printing machine, DIC NA108 was used for the dampening water, and other management conditions were set to the standards recommended by the printing machine manufacturer.

  The test chart image has a configuration in which a plurality of step wedge images having 20%, 50%, 80% mesh and a solid image are arranged in a region managed by different ink keys of the printing press, and the front plane mesh image is a dummy image 24. Was used (ST04).

  Then, a printing operation was performed under the above conditions, and the indigo, red, yellow, and black solid image densities immediately after printing were measured and recorded. At that time, each ink key was set at a different opening so that different density values were obtained in the width direction of the printing press, and sampling was performed while changing the ink feed amount of the entire printing press little by little. Two samples were sampled, the density was measured on one of them, and the other was stored for colorimetry. This work takes into account the possibility that the sample before dry-down will be damaged by the measurement work. As the densitometer, X-Right 408 used for daily printing management was used.

  After the print sample was dried down 24 hours after printing, the step wedge image was measured for color (ST06), and the color difference from the standard colors of the solid and halftone images was calculated. A spectrophotometer spectrophotometer from Gretag was used as the colorimeter, and Excel, a spreadsheet software from Microsoft, was used for the color difference calculation.

  In addition, according to the embodiment of the first invention, the correlation between the solid density and the solid image color difference in the actual measurement result was analyzed. As a result, the management solid density value and the allowable fluctuation range that minimize the color difference from Japan color are 1.48 ± 0.06 for indigo, 1.47 ± 0.07 for red, and 1.00 ± 0 for yellow. .04, black, 1.69 ± 0.12. These values are almost the same as the management density values based on Japan color that have been used empirically in the printing field, and results equivalent to empirical judgment by skilled workers can be obtained in a certain procedure. It was shown that.

  Next, according to the embodiment of the second invention, the correlation between the solid density and the intermediate image color difference in the actual measurement result was analyzed. As a result, for the indigo and black colors, the solid density value at which the color difference is minimum in the halftone images of 20%, 50%, and 80% almost coincided with the standard solid density management value obtained by the above-described procedure. In other words, it was possible to determine that the indigo and black colors were appropriate for Japan Color 2001 under the printing conditions that were implemented.

  Regarding the red color reproduction in this example, the correlation of 50% halftone showed a tendency as shown in FIG. From this result, it is understood that the standard management density value of red should be 1.43 ± 0.04 in consideration of reproduction of halftone. On the other hand, regarding the reproduction of yellow, the 50% halftone correlation showed a tendency as shown in FIG. Accordingly, when the allowable color difference value is 3 or less, the solid color and halftone allowable ranges do not overlap, and it can be seen that the plate making or printing conditions in this example do not conform to Japan Color 2001. Note that when the allowable color difference is 4, there is a range where the solid color and the halftone allowable range overlap, so it can be seen that printing may be performed at a slightly lower density than when the solid color is used as a reference.

  Next, according to the embodiment of the third invention, the correlation between the solid density and the dot gain amount in the yellow reproduction was analyzed, and the necessary correction amount was calculated. In the yellow reproduction, a correlation as shown in FIG. 7 was found between the solid density and the dot gain amount of the 50% halftone image. FIG. 7 uniquely shows that the yellow reproduction in this example has a dot gain of 3% higher than that of the standard printing at the standard density value 15 obtained by the embodiment according to the first invention.

  FIG. 7 shows that in the print reproduction of this embodiment, there is a fluctuation range of about 2% in the dot gain amount even if the solid density value is constant. This fluctuation is offset printing. Is known to be general. Further, in actual sampling of printed matter, the solid density value varies to some extent, so the fluctuation range of the dot gain amount is about 3%, which is the same level as the correction amount obtained by the present invention. Therefore, it is difficult to discriminate whether correction is necessary or simple in the conventional method of simply sampling the printed matter and obtaining the dot gain, and it can be seen that the method of the present invention is superior.

  Create a smooth tone correction curve that converts 50% halftone dots to an area ratio of 47% according to the correction amount indicated by the above method, and use the calibration function that comes with the output machine as a correction curve for the yellow plate output. I input it. After that, a test chart image including a standard color chart image ISO12642 consisting of 928 colors is prepared, and two types of printing plates are created, the conditions for performing the correction process and the conditions for not performing the correction. Printing was performed using the obtained standard solid density value as a management target. One day after printing, the color reproduction of ISO 12642 chart 928 colors was measured with a spectroscan of Gretag, and the average color difference from CIELAB of ISO 12642 chart 928 colors shown in the target Japan Color 2001 Type 3 Calculated.

  As a result, the average color difference was 4.2 under the condition where only the density management during printing was performed without correction during printing plate output, and a relatively good value was obtained. Further, under the condition that the density was controlled during printing after performing the correction process at the time of printing plate output, the average color difference was 2.7, and an excellent result was obtained as the 928 color average color difference value in offset printing. .

  As an example of use of the present invention, in the past, a skilled worker, in accordance with experience, has determined a management density and an allowable frame width to realize color reproduction close to the standard print color, and has performed a management density in a certain procedure. It can be used to obtain the value and allowable variation range, the necessity of correcting the printing conditions, and the correction amount.

The flowchart of embodiment in this invention. An example of a step wedge image which is one embodiment of the present invention. An example of the test chart image which has arrange | positioned the step wedge image which is one embodiment of this invention. An example of the scatter diagram which shows the correlation of the color difference of the solid image density before dry-down which is one embodiment of this invention, and the standard color of the solid image after dry-down. An example of a scatter diagram showing a correlation between a solid image density before dry-down and a color difference between a solid image after dry-down and a standard color of a 50% halftone image, which is an embodiment of the present invention. In the scatter diagram showing the correlation between the solid image density before dry-down and the color difference between the solid image after dry-down and the standard color of the 50% halftone image, which is one embodiment of the present invention, the plate making or printing conditions are An example that is judged inappropriate. An example of a scatter diagram showing a correlation between a solid image density before dry-down and a dot gain amount of a 50% halftone image after dry-down, which is an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Scatter chart of density value and color difference value 2 Density value axis 3 Color difference value axis 4 Typical measurement result in solid image 5 Typical correlation in solid image 6 Typical measurement result in 50% network image 7 Schematic correlation in 50% halftone image 8 Control density value 9 Allowable fluctuation range 10 Allowable fluctuation range considering halftone reproduction 11 Scatter chart of density value and dot gain amount 12 Dot gain amount axis 13 Halftone patch image Actual measurement result 14 Standard value of dot gain 15 Management density value 16 Estimated value of dot gain 17 Difference amount 18 Solid patch image 19A Halftone patch image of 80% network 19B Halftone patch image of 50% network 19C Intermediate of 20% network Tone patch image 20 Step wedge image 21 Test chart image 22a Area managed by specific ink key of printing press 23a Special features of printing press Step wedge image 24 dummy image arranged in the area managed by the ink key

Claims (5)

  For a patch image for print management, measure the density value before dry-down during printing and the colorimetric value after dry-down, and obtain the color difference from the target standard color from the measured colorimetric value. A management method of offset printing, characterized in that a management density value and an allowable variation range at the time of printing are obtained from a non-linear regression analysis of a correlation between a density value and a color difference value.   For step wedge images that have multiple patch images with different halftone dot area ratios that are arranged in the area managed by the same ink key on the printing press, the density value before dry down during the printing operation, and dry down Measure the colorimetric values later, find the color difference from the target standard color from the measured colorimetric values for each patch, and perform nonlinear regression of the correlation between the density value of a specific patch image and the color difference value of each patch image A management method of offset printing, characterized in that a target management density value and an allowable fluctuation range at the time of printing are obtained from analysis.   For step wedge images that have multiple patch images with different halftone dot area ratios that are arranged in the area managed by the same ink key on the printing press, the density value before dry down during the printing operation, and dry down Measure the colorimetric values later, find the color difference from the target standard color from the measured colorimetric values for each patch, and perform nonlinear regression of the correlation between the density value of a specific patch image and the color difference value of each patch image A method for managing offset printing, characterized by evaluating the appropriateness of plate making conditions or printing conditions for a target standard color from analysis.   For step wedge images that have multiple patch images with different halftone dot area ratios that are arranged in the area managed by the same ink key on the printing press, the density value before dry down during the printing operation, and dry down After measuring the density value, the dot gain amount is obtained from the actually measured density value after dry-down, and the linear regression analysis of the correlation between the density value before dry-down of a specific patch image and the dot gain amount of each patch image A method for managing offset printing, wherein a tone correction amount of an output image is calculated from The management of offset printing according to any one of claims 1 to 4, wherein a plurality of management patch images or step wedge images are arranged and measured in image areas managed by different ink keys of a printing press. Method.

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