Web printing production guidelines

In the printing and publishing process, the materials provided to the printing staff must comply with the standards described in the SWOP parameter description. The printing staff assumes that the specific color control is used to ensure faithful reproduction. The following references are published guidelines for five levels of publication using offset offset paper and thermosetting four-color inks as reference.

Guidelines for the production of printing presses. In the past few years, new types of printing presses have become more stable, production speeds have been faster, many printing processes have gradually shifted to positive printing, and more and better measurement and control technologies have emerged. These have been improved. The quality of the print production process. The problem of dot enlargement in the production process of many printing presses has been significantly reduced. In specific press testing conducted by SWOP, the dot enlargement has been controlled at 18% or even lower. In other tests, the dot-ups for printing and publishing remained at about 24% of the standard.

The responsibility of the print production staff is to visually match the printed proofs. Since SWOP specifies a dot gain value of approximately 20% in the proofing, the requirements for the printing production process are even higher and more perfect. Only in this way can the closest matching to the proofs be guaranteed. These guidelines work well (make the print product easier to accept) because it adheres to the guidelines of COLOR BALANCE and PROCESS CONTROL during the printing process. It is well known that in the process of copying, "paper weight" is often less important than color balance and hue shift. It should also be emphasized once again that no matter how high or low an outlet is, it cannot comment on its good or bad. It is harmful if it loses control or instability.

The printer's color control strip must contain a color control strip suitable for measurement on the printed material. The control strip should use 133 lines of screened lines, containing solid blocks of each color; 25%, 50%, and 75% of color blocks; two-color and three-color overprinted solid overprint colors; and visual and ghosting The obvious degree of network expansion. The relationship between the trim size of the publication and the cut size of the web should be within the range that allows the control bar to exist.

The control bar described above can obtain GATF/SWOP product control bar through GATF.

Film copying and plate making In the film copying process, the resolution object control scale and the CT scale should be combined to control the degree of film copying, copying, and plate exposure. Products that meet this requirement include the UGRA Plate Control Scale and the GATF Plate Control Strip.

Positive and Negative Plate Making Although most printed proofs are made using traditional negatives, the printed version of the publication can use both negative and positive plates. Normally, positive-working plates tend to shrink by several percentage points, while negative-working plates tend to increase by several percentage points. In order to meet the needs of removing dirt, cutting, or prolonging the printing life of the printing plate, it is possible to exaggerate the expansion and contraction of outlets during exposure. Due to differences in platemaking procedures, it is normal for 5% or even greater deviations to occur with negative and positive graphic printing. It is recommended that the total dot gain value and the total tonal value increase range used here be sufficiently wide to include platemaking and other differences caused by conventional processing.

Impact of computer-to-plate (CTP) The design of the CTP platesetter is to ensure that the fixed dot percentages in the electronic file are accurately copied onto the plate. The CTP system has a greater ability to change the dot size specified in the electronic file. The CTP needs to be optimized at the time of output so that the final printing effect best matches the provided SWOP proofs.

Super Calendered (SC) paper has some special offset publications printed using Super Dash (SC paper). As with other production materials, the purpose of printing is to visually match the submitted SWOP proofs as closely as possible. The acceptability of the match is up to the customer, but there are some techniques that can improve the potential for matching the SC paper print image with the SWOP proof. If possible, the film and electronic documents provided by the SC paper printing shall meet the following conditions:

The number of screens for the output image should be 120 lines per inch.
According to the performance characteristics of the press, the maximum TAC value should be chosen between 240% and 260%.
The color separation curve is 4% to 6% lower in the midtone portion than the standard SWOP negative color separation curve to compensate for the increase in dot gain values ​​when printed on the SC paper surface.

When providing film or electronic documents for publications printed on the surface of SC paper, check with publishers for specific information.

The printing ink used during the offset printing process of the printing ink is to comply with the Standard Reference Proofing Process Ink of the SWOP/NAPIM standard, and has the physical properties that enable the printing machine to achieve the control parameters of the SWOP printing quality, maintaining the reel Paper printing performance requirements. Manufacturers of printing inks should not deviate from the SWOP/NAPIM reference standard for proofing original color inks and seek to match offset printing color inks.

The density of the central ink used by the ink density printer in the field is the density value read in the center of the SWOP Hi-Lo Color Reference.

The acceptable deviation from this center point is obtained by measuring the difference between the highest density and the lowest density, which is the allowable deviation from the center target point.

Note: Print operators often operate with a high black density. It is therefore necessary to warn the printing operator to ensure that it does not increase beyond the allowable range of the SWOP parameter specification due to dot gain.

The range of acceptable densities for products and proofs obtained through SWOP high and low color references. Note: The actual density range will vary depending on the density meter reading the SWOP high and low color references.
SWOP High and Low Color Reference Density Density Product Density

high
+0.07 +0.14 R=0.28
Medium R=0.14
-0.07
Low -0.14

Total Dot Augmentation/Tonal Value Additions Listed below are the total dot gain values ​​(physical and optical) measured with a 50% 133-line screening object.

Output from electronic documents should be adjusted by the printing industry to match the SWOP samples provided.

In order to maintain a visual gray balance, the dot enlargement values ​​of the three colors should not be much different, and cannot be higher than the target value by 4%. That is, if the cyan or color dot gain is +2% (ie, 24%, it turns out to be 22%), the yellow deviation should not exceed -2% (ie, 18%).

Another way to explain this parameter description is that after the yellow dot gain has increased by two percentage points, the difference between the other primary colors (Y, M, C) cannot exceed four percent.
Target tolerance yellow 20% 15%-25%
Color 22% 17%-27%
Cyan 22% 17%-27%
Black 26% 21%-31%

The contrast of printing contrast is gradually progressive - the general guideline for print publishing is that the print contrast should be within the following range (absolute values, including paper factors):
Yellow 25%-35%
Color or cyan 30%-40%
Black 35%-45%

The responsibility of the printer is to change the hue value on the printing plate at the printing site, so that the submission of approved proofs and film and electronic files matching the color and hue values ​​becomes the responsibility of the printing industry. Therefore, it is necessary for them to control this plate-making step to achieve this goal efficiently, speedily and reproducibly.

Sample and printed signatures of proofs and printed signatures should be viewed and compared under the lighting conditions specified in the ANSI PH2.30-1989 standard.

Reproduced from: Wins