Where should the color scale be placed?
In practical applications, the print operator can place the color patch in any suitable place, such as the upper or lower edge of the paper or sheet format, the head trim area, and the gutter portion printed along the cylinder. Although this last option is not appropriate because it can only provide channel information to the printer's ink supply system, measuring some data and observing these data limits is always better than nothing.
In the most ideal case or where maximum control is required and where typesetting positions permit, the color mark is placed across the layout page, parallel to the fountain roller, and as close as possible to the center of the page in the page because of the head and tail of the page. It is more likely to change at the edge. This placement method can measure across the length of the print, providing good print information for the entire paper.
Note: Avoid placing the color patch where it can be folded, cut, or punched. All of these will hinder or destroy the measurements obtained by printing color patches.
Recommendation: If time and materials allow, it is best to use the same color coded film to print jobs and test plates placed on the top edge, center, bottom edge, and along the drum. In the test layout, images are to be included, printed, and the images are matched with the pre-proof proofs of the test layout, and then some printing features are selected while ensuring that the printing press is stable. Measure the color patches at these four locations and compare their dot gain values, density values, and other measurement data. Through these operations, you can be aware of the effect of different color patch positions on the measurement data, including whether or not a color code placed in the direction of the roller can provide more information on the test print copy reproduction status.
What if I can't place a complete color patch in the layout?
Experts suggest that the printing operator should place at least one solid color patch for each color, and a correspondingly colored 75% density patch, at least somewhere in the layout, or in a specially designed icon or other customer-approved element. , including black, even if these eight color blocks are to be placed in the gutter. The reason for this suggestion is that the printing quality of the dark tone area directly affects the quality of the entire printed product, and the human eye is also sensitive to the resolution of this part. The measurement of print contrast is a more technical term that can be obtained by measuring field objects and 75% color blocks, and can be used to facilitate the transmission of print quality information.
If it is not possible to use a full color scale in each job, you can choose to use the color scale in as many jobs as possible, or use the full color scale at least in stages, such as once a week or once a month. This will help identify problems during actual job evaluation and analyze the causes of the problems. Keep in mind that it is better to measure than without any measurement. Also note that if someone controls the production process, the quality of the product will be better.
Can the back of the color mark be printed again?
If you use a standard black backing material such as BackStopTM during colorimetric measurements, it is irrelevant whether the backside of the colormark is still printed because the black backing eliminates the measurement variations that result from the pattern printed on the reverse side of the sheet.
If you do not use a black backing material, the back of the printed color label should not be printed with any pattern in order to ensure the most accurate measurement analysis. Because any paper is not completely opaque, printing on the reverse side of the paper is measured by the densitometer and affects the final measurement. (Note: The results of the measurement with a black lining cannot be compared with the measurements without a black lining, nor with the objects printed with a pattern on the back.)
The ANSI/ISO standard requires a black backing for measurements, but since most printing companies print color patches on the same side of a printed sheet, this saves space and facilitates layout, so most of them do not use black backs. Lining.
Even if the logo is printed on the back of the logo and there is no black backing, it is better to print and measure the data on the color scale. Just be aware that this type of measurement is more affected by additional variables than other jobs and the results will be slightly different. As mentioned earlier, it is better to measure than to measure.
Why should a black backing be better than a gray or white backing when measuring proofs or prints?
ANSI/ISO 5/4-1983 (R.1986) - ANSI PH 2.17-1985: Density Measurements Geometric Conditions for Reflection Densitometry (Geometric Observation Conditions for Densitometry in Reflectance Densitometry) defines geometric observation conditions for reflection density measurements . This standard data contains the following description:
"This International Standard specifies that the surface of the material on the backside of the sample to be tested should be spectrally non-selective and diffusely reflective, and that the ISO reflection density value is 1.50 ± 0.20, which is very important. [Caution: Spectral non-selective The surface is a gray surface; gray shades with reflectance values ​​around 1.50 should appear black.] Some reflection density standards usually specify that the backing material should have a lower reflection density." Annex A of the standard further explains: " When defining the reflection density in well-defined observation conditions, it is very important to determine the characteristics of the material used behind the sample."
According to the document, there are many reasons for choosing a black backing, including:
1. The black backing reduces the variables in the measurement process. Since many of the samples used in the printing and publishing process are usually not completely opaque, the pattern printed on the reverse side of the paper affects the measurement results, and sometimes has a great influence, so this is for the purpose of measurement and process control. The point is very important. Surveys by the PSI Association have shown that when measuring substrates with transmission densities equal to or less than 1.00, different backing materials and patterns printed on the reverse side of the material can affect the measurement results.
2. From the point of view of spectrum, density and physical requirements, the use of backing materials can greatly reduce the measurement data of low-density surfaces.
3. The absorbance ratio can be calculated directly from the density reading using a black backing.
The standard also warns that samples in the printing industry are usually backed by two or more layers of the same backing material. The fact that the sample ISO density values ​​combined with the density values ​​of the printing image and the printing material cannot be read together is totally unproven, although some precautionary measures are taken to determine that the reading is a combination of the image and the printing material, not the image layer itself Readings.
The change in measured values ​​due to the absence of standard backing materials continues to increase as the paper becomes thinner and the value of the projected density decreases. The initial survey conducted by the PSI Association on this aspect showed that for the printing industry paper, the paper's delta density values ​​were reduced from 0.07 to 0.002 under both black and white backing conditions, and in the same case the transmission density values. It will increase from 0.3 to 1.2. From the data we can see that the difference between the transmission density of the substrate and the data of the same material measured under black and white different backings is exponential. The white backing used in this study was a non-selectively-absorbed material that was used to coat pottery tiles on white steel. It was non-fluorescent and had a reflectance of 89%. The black backing used was a GCA BackStopTM standard blackboard and complied with ANSI. /ISO regulations. In order to actually observe the value of the paper's transmission density, the PSI Association examined several different types of paper and found that the transmission density values ​​for thin papers used in multi-page publications and the Bible were around 0.30; 20-pound white offset printing The paper has a transmission density value of about 0.60; an 80-pound coated card material has a transmission density value of about 0.90; and a 120-pound coated card material has a transmission density value of about 1.20. These investigations also showed that the situation of the photographic paper is similar but there are different curves.
Realizing that black backing minimizes changes in measurement results, it is recommended to use a standard black backing under the following conditions:
l equipment installation;
Calibration of the instrument (Note: The use of a calibrated black backing during the installation of the densitometer is very important, as this backing is defined in the ANSI/ISO density standard.);
l specification of job parameters (for example, printing a job to determine the target point) unless a different backing is specified;
l specification of industry parameters (for example, printing types of products such as magazine advertisements to determine target points), unless a different backing is specified;
• Communication of measurement data between different organizations unless a different backing is specifically designated.
For internal users, for example, if an operator subjectively estimates an image and compares it with a proof or another model, the black backing will make the appearance of the printed image feel slightly different. . As suggested in the standard, in these cases it is very likely that the operator will place one or several unprinted substrates under the paper and then evaluate them.
Members of many international organization groups plan to develop a standard white backing. This backing standard must redefine the following parameters:
l Color
l Brightness
l Surface diffusion phenomenon
l Fluorescence
l Density In order to ensure the information transmission of measurement results, it is necessary to record each of the above factors when using a white backing to ensure that the recipient of the measurement results can understand the operation of these measurement results.
From the point of view of the metrics and the user's position, the currently used standard has a certain degree of stability, the convenience of using a black backing (existing materials, and universal under various conditions, to ensure consistency with the current ANSI standards) The challenge of defining white backings has shown that the development of white backing standards does not help to reduce the changes in measurement results, nor does it reduce the user application of standard backing materials.
In general, in color measurement for measurement and process control, the industry recommends the use of a standard black backing. This should be the standard method to ensure that these measurements are not affected by factors such as the reverse side of the paper or the discomfort of the image on the paper. The printing materials should not be stacked during the measurement. First, if a black backing is not used during the density measurement, the user should communicate the information of the backing used, and also know that this measurement is affected by additional changes. The degree of influence of these changing factors can be determined by comparing the readings of the same paper material with and without the standard black backing.
In practical applications, the print operator can place the color patch in any suitable place, such as the upper or lower edge of the paper or sheet format, the head trim area, and the gutter portion printed along the cylinder. Although this last option is not appropriate because it can only provide channel information to the printer's ink supply system, measuring some data and observing these data limits is always better than nothing.
In the most ideal case or where maximum control is required and where typesetting positions permit, the color mark is placed across the layout page, parallel to the fountain roller, and as close as possible to the center of the page in the page because of the head and tail of the page. It is more likely to change at the edge. This placement method can measure across the length of the print, providing good print information for the entire paper.
Note: Avoid placing the color patch where it can be folded, cut, or punched. All of these will hinder or destroy the measurements obtained by printing color patches.
Recommendation: If time and materials allow, it is best to use the same color coded film to print jobs and test plates placed on the top edge, center, bottom edge, and along the drum. In the test layout, images are to be included, printed, and the images are matched with the pre-proof proofs of the test layout, and then some printing features are selected while ensuring that the printing press is stable. Measure the color patches at these four locations and compare their dot gain values, density values, and other measurement data. Through these operations, you can be aware of the effect of different color patch positions on the measurement data, including whether or not a color code placed in the direction of the roller can provide more information on the test print copy reproduction status.
What if I can't place a complete color patch in the layout?
Experts suggest that the printing operator should place at least one solid color patch for each color, and a correspondingly colored 75% density patch, at least somewhere in the layout, or in a specially designed icon or other customer-approved element. , including black, even if these eight color blocks are to be placed in the gutter. The reason for this suggestion is that the printing quality of the dark tone area directly affects the quality of the entire printed product, and the human eye is also sensitive to the resolution of this part. The measurement of print contrast is a more technical term that can be obtained by measuring field objects and 75% color blocks, and can be used to facilitate the transmission of print quality information.
If it is not possible to use a full color scale in each job, you can choose to use the color scale in as many jobs as possible, or use the full color scale at least in stages, such as once a week or once a month. This will help identify problems during actual job evaluation and analyze the causes of the problems. Keep in mind that it is better to measure than without any measurement. Also note that if someone controls the production process, the quality of the product will be better.
Can the back of the color mark be printed again?
If you use a standard black backing material such as BackStopTM during colorimetric measurements, it is irrelevant whether the backside of the colormark is still printed because the black backing eliminates the measurement variations that result from the pattern printed on the reverse side of the sheet.
If you do not use a black backing material, the back of the printed color label should not be printed with any pattern in order to ensure the most accurate measurement analysis. Because any paper is not completely opaque, printing on the reverse side of the paper is measured by the densitometer and affects the final measurement. (Note: The results of the measurement with a black lining cannot be compared with the measurements without a black lining, nor with the objects printed with a pattern on the back.)
The ANSI/ISO standard requires a black backing for measurements, but since most printing companies print color patches on the same side of a printed sheet, this saves space and facilitates layout, so most of them do not use black backs. Lining.
Even if the logo is printed on the back of the logo and there is no black backing, it is better to print and measure the data on the color scale. Just be aware that this type of measurement is more affected by additional variables than other jobs and the results will be slightly different. As mentioned earlier, it is better to measure than to measure.
Why should a black backing be better than a gray or white backing when measuring proofs or prints?
ANSI/ISO 5/4-1983 (R.1986) - ANSI PH 2.17-1985: Density Measurements Geometric Conditions for Reflection Densitometry (Geometric Observation Conditions for Densitometry in Reflectance Densitometry) defines geometric observation conditions for reflection density measurements . This standard data contains the following description:
"This International Standard specifies that the surface of the material on the backside of the sample to be tested should be spectrally non-selective and diffusely reflective, and that the ISO reflection density value is 1.50 ± 0.20, which is very important. [Caution: Spectral non-selective The surface is a gray surface; gray shades with reflectance values ​​around 1.50 should appear black.] Some reflection density standards usually specify that the backing material should have a lower reflection density." Annex A of the standard further explains: " When defining the reflection density in well-defined observation conditions, it is very important to determine the characteristics of the material used behind the sample."
According to the document, there are many reasons for choosing a black backing, including:
1. The black backing reduces the variables in the measurement process. Since many of the samples used in the printing and publishing process are usually not completely opaque, the pattern printed on the reverse side of the paper affects the measurement results, and sometimes has a great influence, so this is for the purpose of measurement and process control. The point is very important. Surveys by the PSI Association have shown that when measuring substrates with transmission densities equal to or less than 1.00, different backing materials and patterns printed on the reverse side of the material can affect the measurement results.
2. From the point of view of spectrum, density and physical requirements, the use of backing materials can greatly reduce the measurement data of low-density surfaces.
3. The absorbance ratio can be calculated directly from the density reading using a black backing.
The standard also warns that samples in the printing industry are usually backed by two or more layers of the same backing material. The fact that the sample ISO density values ​​combined with the density values ​​of the printing image and the printing material cannot be read together is totally unproven, although some precautionary measures are taken to determine that the reading is a combination of the image and the printing material, not the image layer itself Readings.
The change in measured values ​​due to the absence of standard backing materials continues to increase as the paper becomes thinner and the value of the projected density decreases. The initial survey conducted by the PSI Association on this aspect showed that for the printing industry paper, the paper's delta density values ​​were reduced from 0.07 to 0.002 under both black and white backing conditions, and in the same case the transmission density values. It will increase from 0.3 to 1.2. From the data we can see that the difference between the transmission density of the substrate and the data of the same material measured under black and white different backings is exponential. The white backing used in this study was a non-selectively-absorbed material that was used to coat pottery tiles on white steel. It was non-fluorescent and had a reflectance of 89%. The black backing used was a GCA BackStopTM standard blackboard and complied with ANSI. /ISO regulations. In order to actually observe the value of the paper's transmission density, the PSI Association examined several different types of paper and found that the transmission density values ​​for thin papers used in multi-page publications and the Bible were around 0.30; 20-pound white offset printing The paper has a transmission density value of about 0.60; an 80-pound coated card material has a transmission density value of about 0.90; and a 120-pound coated card material has a transmission density value of about 1.20. These investigations also showed that the situation of the photographic paper is similar but there are different curves.
Realizing that black backing minimizes changes in measurement results, it is recommended to use a standard black backing under the following conditions:
l equipment installation;
Calibration of the instrument (Note: The use of a calibrated black backing during the installation of the densitometer is very important, as this backing is defined in the ANSI/ISO density standard.);
l specification of job parameters (for example, printing a job to determine the target point) unless a different backing is specified;
l specification of industry parameters (for example, printing types of products such as magazine advertisements to determine target points), unless a different backing is specified;
• Communication of measurement data between different organizations unless a different backing is specifically designated.
For internal users, for example, if an operator subjectively estimates an image and compares it with a proof or another model, the black backing will make the appearance of the printed image feel slightly different. . As suggested in the standard, in these cases it is very likely that the operator will place one or several unprinted substrates under the paper and then evaluate them.
Members of many international organization groups plan to develop a standard white backing. This backing standard must redefine the following parameters:
l Color
l Brightness
l Surface diffusion phenomenon
l Fluorescence
l Density In order to ensure the information transmission of measurement results, it is necessary to record each of the above factors when using a white backing to ensure that the recipient of the measurement results can understand the operation of these measurement results.
From the point of view of the metrics and the user's position, the currently used standard has a certain degree of stability, the convenience of using a black backing (existing materials, and universal under various conditions, to ensure consistency with the current ANSI standards) The challenge of defining white backings has shown that the development of white backing standards does not help to reduce the changes in measurement results, nor does it reduce the user application of standard backing materials.
In general, in color measurement for measurement and process control, the industry recommends the use of a standard black backing. This should be the standard method to ensure that these measurements are not affected by factors such as the reverse side of the paper or the discomfort of the image on the paper. The printing materials should not be stacked during the measurement. First, if a black backing is not used during the density measurement, the user should communicate the information of the backing used, and also know that this measurement is affected by additional changes. The degree of influence of these changing factors can be determined by comparing the readings of the same paper material with and without the standard black backing.
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