Color standard application (four)
We are a big printing company in Shenzhen China . We offer all book publications, hardcover book printing, papercover book printing, hardcover notebook, sprial book printing, saddle stiching book printing, booklet printing,packaging box, calendars, all kinds of PVC, product brochures, notes, Children's book, stickers, all kinds of special paper color printing products, game cardand so on.
For more information please visit
http://www.joyful-printing.com. ENG only
http://www.joyful-printing.net
http://www.joyful-printing.org
email: info@joyful-printing.net
Where should the color scale be placed?
In practical applications, the print operator can place the color mark in any suitable place, such as the top or bottom edge of the paper or sheet format, the trimming area at the head, and the portion of the gutter that is printed along the roll. Although this last option is not appropriate because it only provides channel information for the printer's ink supply system, it is better to measure some data and observe the limits of the data than to measure nothing.
In the most ideal case, or where maximum control and layout position are allowed, the color code is placed across the layout page, parallel to the ink supply roller, and as close as possible to the center of the printed page, because at the beginning and end of the layout page There is a greater likelihood of changes at the edges. This type of placement allows for the measurement of the length across the print and provides excellent print information for the entire paper.
CAUTION Avoid placing the color code where it may be folded, cut, or punched. These will hinder or destroy the measurements obtained by the printed color code.
Recommendations If time and materials permit, it is best to print the job and test version with the same color-coded film, placed on top, center, bottom and along the drum. In the test layout, you should include a picture, print it, match the picture with the pre-sample of the test layout, and then select some print features while keeping the press stable. The color scales of these four positions are measured separately, and their dot gain values, density values, and other measurement data are compared. Through these operations, it is possible to realize the influence of the different position of the color mark on the measurement data, including whether a color mark placed in the direction of the roller can provide more information on the copying condition of the test layout.
What if I can't place a full color patch in the layout?
Experts recommend that the print operator should place at least somewhere in the layout, or in a specially designed icon or other customer-approved element, a solid color block for each color, and a 75% density color block for the corresponding color. , including black, even if the eight patches are to be placed in the gutter. The reason for suggesting this is because the printing quality of the dark-adjusted area directly affects the quality of the entire printed product, and the human eye is more sensitive to the resolution of this part. The measurement of print contrast is a more technical term that can be obtained by measuring the field object and the 75% chromaticity block, and can be used to convey the quality of the print.
If it is not possible to use a full color scale in every assignment, you can choose to use the color scale in as many jobs as possible, or at least to use the full color scale in stages, such as once a week or once a month. This helps to identify problems in the actual job evaluation and analyze the cause of the problem. Remember to take measurements is better than no measurement. Also note that if someone controls the production process, the quality of the product will be better.
Can the back of the color code be printed again?
If you use a standard black backing material such as BackStopTM during the measurement of the color scale, it does not matter if the back side of the color standard is still printed, because this black backing eliminates the measurement variations caused by the pattern printed on the reverse side of the printed sheet.
If you are not using a black backing material, in order to ensure the most accurate measurement analysis, the back of the printed color standard should not print any pattern. Because any paper is not completely opaque, the printing on the reverse side of the paper is measured by a densitometer, affecting the final measurement. (Note: The results of measurements with a black lining cannot be compared to measurements without a black lining, nor can they be compared to objects with a back printed pattern.)
The ANSI/ISO standard stipulates that black backing should be used for measurement, but since most printing companies print color marks at the same position on both sides of the printed sheet, this saves space and facilitates layout, so most of them do not use black back. Lined up.
Even if other patterns are printed on the back of the color standard and there is no black backing on hand, it is better to print and measure the data on the color standard than it is. Just be aware that such measurements are more affected by additional variables than others, and the results will be slightly different. As mentioned earlier, it is better to take measurements than to measure them.
Why is it better to use a black backing 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 defines the geometric observation conditions for reflection density measurements. . This standard material contains the following introduction:
“This International Standard specifies that the material surface on the back side 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. This is very important. [Note: Spectral non-selective The surface is a gray surface; the gray tone with a reflection density value of approximately 1.50 should show black.] Some reflection density standards usually specify a lower reflection density for the backing material." Standard Annex A further explains: "In When determining the reflection density in well-defined observation conditions, it is important to determine the characteristics of the material used behind the sample."
According to this document, there are many reasons for choosing a black backing, including:
• 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 and sometimes even has a large impact, so for operations for metrics and process control purposes. The point is very important. According to a survey by the PSI Association, when measuring a substrate with a transmission density of 1.00 or less, different backing materials and reverse printed patterns of the material will affect the measurement results.
• The use of backing materials can greatly reduce measurement data on low-density surfaces in terms of spectrum, density, and physical requirements.
• Use a black backing to calculate the absorption ratio directly from the density reading.
The standard also warns that samples in the printing industry are usually backed by two or more layers of the same backing material. There is no reason why the ISO density values of the samples combined with the density values of the substrate and the substrate cannot be read together, although some precautions are taken to determine the readings that combine the image and the substrate, not the image layer itself. The reading.
The change in measured values due to the absence of standard backing materials is increasing as the paper becomes thinner and the value of the projected density decreases. The initial survey conducted by the PSI Association showed that for paper in the printing industry, the delta density value of the paper decreased from 0.07 to 0.002 under the conditions of black and white backing, and the transmission density value under the same conditions. It will increase from 0.3 to 1.2. From the data, we can see that the transmission density of the substrate and the difference between the data measured by the same material under different backings in black and white are exponential. The white backing used in this investigation is a non-selectively absorbing ceramic tiled material on white steel with no fluorescence and a reflection coefficient of 89%. The black backing is a GCA BackStopTM standard blackboard that is ANSI-compliant. /ISO regulations. In order to actually observe the transmission density values of paper, the PSI Institute examined several different papers and found that the thinner papers used for multi-page publications and the Bible have a transmission density value of about 0.30; 20 lb white cloth offset printing The paper has a transmission density value of about 0.60; the 80 lb. coated card material has a transmission density value of about 0.90; and the 120 lb. coated card material has a transmission density of about 1.20. These surveys also show that photographic papers are similar but have different curves.
Be aware that the black backing minimizes variations in measurement results, so a standard black backing is recommended in the following situations:
• Instrument installation;
• Calibration of the instrument (Note: The calibration of the black backing used during the densitometer installation is very important as it is defined in the ANSI/ISO density standard);
• job parameter specifications (eg, printing a job to determine the target point) unless a different backing is specified;
• Industry parameter specifications (for example, the type of printing of products such as magazine advertisements to determine the target point) unless a different backing is specified;
• Exchange measurement data between different organizations unless a different backing is specified.
For internal users, for example, an operator subjectively estimates an image and compares it to a sample or another model. The black backing will make the printed image look slightly different, which is less suitable. . As suggested in the standard, in these cases it is likely that the operator will place one or more unprinted substrates under the paper and evaluate them.
Members of many international organizations plan to develop a standard white backing. The standard for this backing must redefine the following parameters:
·Color
·Brightness
·Surface diffusion
·Fluorescence
·Density
In order to ensure the information transfer of the measurement results, each of the above factors should be recorded when using the white backing to ensure that the recipient of the measurement results can understand the operation of these measurement results.
From the two perspectives of metrics and user positions, the currently used standards have certain stability, the convenience of using black backing (existing materials, and common under various conditions, to ensure consistency with current ANSI standards) The challenge of defining a white backing has shown that the development of a white backing standard does not help to reduce variations in measurement results or to reduce the level of user application of standard backing materials.
In general, the industry recommends the use of standard black backing for color measurement for measurement and process control purposes. This should be the standard method to ensure that these measurements are not affected by factors such as reverse printing on the paper or disproportionate image on paper. The substrates should not be stacked together during the measurement process. First, if a black backing is not used in the density measurement process, the user should communicate the information about the backing used and also know that the measurement is affected by additional factors. The extent of these varying factors can be determined by comparing the measured readings of the same paper material with and without the standard black backing.