There are currently at least two situations where digital proofing technology must be used: First, the final result of the prepress operation is directly recorded on the plate. This is known as computer-to-plate (CTP); the second situation is that the prepress preparation result is directly Digital printing system output. In both cases, the step of outputting the post-printing film is skipped. There is no reason to use the profiling process for analog offset printing.
First, digital proofing and digital printing
From the computer to the proofs and digital printing with the principle of difference, the only difference is the output speed and output purposes. The digital graphic output aimed at proofing uses a technology similar to digital printing. Its focus is on checking how the results of the digital workflow will be displayed during actual printing, and as a technical basis for large-volume printing. Due to this feature, the speed requirement for digital proofing equipment is not the main factor. The key is the gap between the results of digital proofing and the actual printed matter. Through years of hard work, with the participation of color management systems, digital proofing results have become more and more close to traditional offset printing, and have been accepted by more and more printers.
Digital Proofing is a key technology that supports CTP workflow-based printing of an overall digital workflow. It not only involves customers but also affects the printing shop. Both the customer and the press operator are required to receive the most basic training in various digital proofing technologies. They should be made aware of the copying technology characteristics adopted by different digital proofing technologies, as well as the screening technology determined by the copying characteristics and corresponding to the color reproduction requirements. The number and limits of the number of screens can be achieved. The press operator must abandon the analog half-tone proofing process, telling them that even if the traditional printing process is to achieve the same effect as the digital proofing, it is not difficult.
Second, the characteristics of CTP workflow
The CTP work flow omits the process of outputting to the film, and the phenomenon that the photosetter records the growth of color images will no longer exist. Therefore, an important feature of the CTP workflow is that the dot enlargement is much smaller than the use of film to record and reprint. Therefore, the output curve (transfer function) when the page is recorded on the imagesetter cannot be used; the press operator must also understand the CTP seal. The difference between the version and the PS version requires different ink balance adjustment parameters. When the metal CTP plate is intended to be used in the workflow, the printing conditions will also change due to the decrease in the dot gain value, which will affect the ink density setting and the leveling curve of the image. In contrast to traditional workflows, staplers need guidance so that the large format digitally discharged can meet all printing and binding requirements.
The key issue in implementing the CTP process is to solve digital proofing. Digital proofing is imperative once the film has been removed from the workflow. In theory, digital proofing results should reflect the same halftone dot shape, number of screen lines, and gradation variations as the printing process. However, most digital proofing methods generally cannot simulate the halftone dot properties in actual printing, because some digital proofing devices do not use halftone screening technology to simulate continuous tone originals (such as continuous tone digital proofing devices), even if The digital proofing system based on halftone technology may not necessarily produce the same dot structure as the CTP plate. The proofing and plate generation in the CTP process are two independent processes. Therefore, the dots on the sample draft and the dots on the printed matter are played. It is often different. Therefore, the user must notice that the digital proofing and recording to the plate are two RIP processes, which is the main reason why the proofs and plates have different levels of change and resolution. In fact, the printing company should understand that even if the analog proofing or offset proofing process is used, whether the proofing result reflects the actual production effect of the printing process is also uncertain.
Third, digital proofing points
Printing companies and their customers have not reached the point of freedom in the digital proofing process during the transition from analog to digital workflows, because this change is not easy or even difficult and takes time. The press operator needs time to learn how to match the print results with the results of the proofing, rather than using the dot-to-point analogy as before. Note that it is important to match the printed colors with the results of the proofing rather than using a magnifying glass to check the proximity of the printed dots to the proofing dots. This change in mind is a prerequisite for accepting the digital proofing process. In order to check whether the print color matches the color of the proofs, it is first necessary to observe under the standard light source. For the prints with low quality requirements, visual inspections can be used; however, for those with high quality requirements for printed matter, instrument inspections are required. A typical densitometer can only measure optical density. When the demand is high, a spectrodensitometer or similar device can be used to measure the actual color values ​​of proofs and prints.
Fourth, digital proofing technology
There are two types of digital color proofing methods. One is halftone proofing, and the other is continuous proof proofing. Each of the two proofing methods has its own technical implementation, such as Laser Dye Removal technology, color spray. Ink replication technology, dye sublimation technology, laser color printing technology, and thermal transfer replication technology. Each digital proofing technology has its advantages and disadvantages, and the prices of equipment and consumables may vary greatly. But as long as proper management and calibration are performed, each digital proofing technology produces a very accurate color.
When discussing digital proofing techniques, it is not possible to consider only the advantages and disadvantages of various color proofing techniques. It is also necessary to judge every proofing technique from an economic perspective. For example, inkjet replication technology and dye thermal sublimation technology can produce very accurate color proofing, but the cost of the two is different. Therefore, finding the right digital proofing method for each customer is not a simple matter, because the customer's requirements and preferences are varied.
Fifth, page proofing and spelling proofing
Color proofing is important, and page proofing and imposition proofing should occupy an equally important position. The purpose of page proofing is to check the fonts, linework and layout. This kind of proofing should begin early in the production cycle. If the user equipment has the ability to combine page proofing and color proofing, the page proofing can be combined with the color proofing, but the two should be independent and can be clearly distinguished from each other.
The transfer of prepress preparation results to large format output also requires some type of imposition proofing system and a system that calibrates color proofing equipment. The operator must confirm that the pages of each publication have been placed in accordance with the requirements of the book, and that the page numbers have been rationally imposed according to folds and saddle stitching. The equipment used for proofing the layout results is usually a large-format inkjet printer, such as the Atlas produced by Agfa, which is a continuous drum proofing device. If Apogee workflow software developed by Agfa Corporation is purchased, its RIP and output management module Print Drive support special preview function, which can carefully check the job to be output before outputting.
Layout proofing is to check the correctness of the operation as a whole. If the layout of the layout is not reasonable, the printing and binding workshop will be at a loss. Therefore, the prepress and platemaking departments should have regular communication with the printing and binding workshops. Understanding each other is the fundamental method to prevent rework.
First, digital proofing and digital printing
From the computer to the proofs and digital printing with the principle of difference, the only difference is the output speed and output purposes. The digital graphic output aimed at proofing uses a technology similar to digital printing. Its focus is on checking how the results of the digital workflow will be displayed during actual printing, and as a technical basis for large-volume printing. Due to this feature, the speed requirement for digital proofing equipment is not the main factor. The key is the gap between the results of digital proofing and the actual printed matter. Through years of hard work, with the participation of color management systems, digital proofing results have become more and more close to traditional offset printing, and have been accepted by more and more printers.
Digital Proofing is a key technology that supports CTP workflow-based printing of an overall digital workflow. It not only involves customers but also affects the printing shop. Both the customer and the press operator are required to receive the most basic training in various digital proofing technologies. They should be made aware of the copying technology characteristics adopted by different digital proofing technologies, as well as the screening technology determined by the copying characteristics and corresponding to the color reproduction requirements. The number and limits of the number of screens can be achieved. The press operator must abandon the analog half-tone proofing process, telling them that even if the traditional printing process is to achieve the same effect as the digital proofing, it is not difficult.
Second, the characteristics of CTP workflow
The CTP work flow omits the process of outputting to the film, and the phenomenon that the photosetter records the growth of color images will no longer exist. Therefore, an important feature of the CTP workflow is that the dot enlargement is much smaller than the use of film to record and reprint. Therefore, the output curve (transfer function) when the page is recorded on the imagesetter cannot be used; the press operator must also understand the CTP seal. The difference between the version and the PS version requires different ink balance adjustment parameters. When the metal CTP plate is intended to be used in the workflow, the printing conditions will also change due to the decrease in the dot gain value, which will affect the ink density setting and the leveling curve of the image. In contrast to traditional workflows, staplers need guidance so that the large format digitally discharged can meet all printing and binding requirements.
The key issue in implementing the CTP process is to solve digital proofing. Digital proofing is imperative once the film has been removed from the workflow. In theory, digital proofing results should reflect the same halftone dot shape, number of screen lines, and gradation variations as the printing process. However, most digital proofing methods generally cannot simulate the halftone dot properties in actual printing, because some digital proofing devices do not use halftone screening technology to simulate continuous tone originals (such as continuous tone digital proofing devices), even if The digital proofing system based on halftone technology may not necessarily produce the same dot structure as the CTP plate. The proofing and plate generation in the CTP process are two independent processes. Therefore, the dots on the sample draft and the dots on the printed matter are played. It is often different. Therefore, the user must notice that the digital proofing and recording to the plate are two RIP processes, which is the main reason why the proofs and plates have different levels of change and resolution. In fact, the printing company should understand that even if the analog proofing or offset proofing process is used, whether the proofing result reflects the actual production effect of the printing process is also uncertain.
Third, digital proofing points
Printing companies and their customers have not reached the point of freedom in the digital proofing process during the transition from analog to digital workflows, because this change is not easy or even difficult and takes time. The press operator needs time to learn how to match the print results with the results of the proofing, rather than using the dot-to-point analogy as before. Note that it is important to match the printed colors with the results of the proofing rather than using a magnifying glass to check the proximity of the printed dots to the proofing dots. This change in mind is a prerequisite for accepting the digital proofing process. In order to check whether the print color matches the color of the proofs, it is first necessary to observe under the standard light source. For the prints with low quality requirements, visual inspections can be used; however, for those with high quality requirements for printed matter, instrument inspections are required. A typical densitometer can only measure optical density. When the demand is high, a spectrodensitometer or similar device can be used to measure the actual color values ​​of proofs and prints.
Fourth, digital proofing technology
There are two types of digital color proofing methods. One is halftone proofing, and the other is continuous proof proofing. Each of the two proofing methods has its own technical implementation, such as Laser Dye Removal technology, color spray. Ink replication technology, dye sublimation technology, laser color printing technology, and thermal transfer replication technology. Each digital proofing technology has its advantages and disadvantages, and the prices of equipment and consumables may vary greatly. But as long as proper management and calibration are performed, each digital proofing technology produces a very accurate color.
When discussing digital proofing techniques, it is not possible to consider only the advantages and disadvantages of various color proofing techniques. It is also necessary to judge every proofing technique from an economic perspective. For example, inkjet replication technology and dye thermal sublimation technology can produce very accurate color proofing, but the cost of the two is different. Therefore, finding the right digital proofing method for each customer is not a simple matter, because the customer's requirements and preferences are varied.
Fifth, page proofing and spelling proofing
Color proofing is important, and page proofing and imposition proofing should occupy an equally important position. The purpose of page proofing is to check the fonts, linework and layout. This kind of proofing should begin early in the production cycle. If the user equipment has the ability to combine page proofing and color proofing, the page proofing can be combined with the color proofing, but the two should be independent and can be clearly distinguished from each other.
The transfer of prepress preparation results to large format output also requires some type of imposition proofing system and a system that calibrates color proofing equipment. The operator must confirm that the pages of each publication have been placed in accordance with the requirements of the book, and that the page numbers have been rationally imposed according to folds and saddle stitching. The equipment used for proofing the layout results is usually a large-format inkjet printer, such as the Atlas produced by Agfa, which is a continuous drum proofing device. If Apogee workflow software developed by Agfa Corporation is purchased, its RIP and output management module Print Drive support special preview function, which can carefully check the job to be output before outputting.
Layout proofing is to check the correctness of the operation as a whole. If the layout of the layout is not reasonable, the printing and binding workshop will be at a loss. Therefore, the prepress and platemaking departments should have regular communication with the printing and binding workshops. Understanding each other is the fundamental method to prevent rework.
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