Feel the color management around you (5)

2. Workflow issues

Workflow is the process of production. Each process that a product passes through in the production process is a process. An operation in a process is a process, and it is also a process to integrate all the processes that produce a product. This entire process of arranging all production processes from start to finish is often referred to as a workflow. The printing and copying of images was originally a very complicated process, but due to the development and application of modern science and technology, especially computer technology, this process has been greatly simplified. Some of the original printing professions, such as image scanning, processing, correction, and combination, have also slowly started to peel off from the printing profession. The simplification of the process has greatly reduced the variable factors affecting the quality of the printed product during the copying process, and the quality of the product has been greatly improved, but it also makes every operation critical.

A printing product enters the plate-making stage after completing the computer's pre-processing. Assuming that the company's platemaking equipment includes imagesetters, processor, plateetters, and plateetters, there are four working processes at this stage, but it is customary to consider the two processes of film output and platemaking. The printing plate produced at this stage is provided for proofing or printing.
Traditionally, it is considered that plate making, proofing and printing are three processes in the printing process. In fact, plate making - proofing and plate making - printing are two separate processes. Because printing and proofing are all final products, not intermediate products.
From this process configuration, it can be seen that the quality of the final product mainly depends on the various devices that make up this process. As the “bucket effect” puts it, the final quality of the product is determined by the shortest piece of wood that makes up the bucket. The quality of this printed product also depends on the worst state of the equipment. Of course, the formation of "bucket effect" also includes factors such as operation, materials, environment, and process management. With the best equipment, the best materials, and first-rate operators, there is no corresponding management system, and it is also difficult to produce first-rate products. Analysis of the film, printing and printing process. As long as the film output process is normal, it is often checked to adjust the output linearization, and the resulting film is generally not a problem. The printing process due to the light source and inhalation and Other reasons will cause dot network shrinkage problem, that is, drying the dots on the printing plate to the center of the network, the dot area is smaller than the original. Usually, the smaller the dot shrink is, the bigger dot is better. A device with a slightly poorer state usually causes 1% of small dots to disappear, resulting in an out of network and affecting the reproduction of the image's high-light levels.

The third process is printing. In this process, the area of ​​the printing dots will increase, which is exactly the opposite of the phenomenon in the printing plates. The smaller the dots that are transferred to the objects to be printed, the larger the dot area ratio of the dots relative to the dots. Although, to a certain extent, this compensates for the reduction in dot area produced by the printing process, the change relationship does not fully correspond, and it will still have a certain influence on the image level reproduction. In particular, small dots that are not dried during the printing process will not be reproduced. What's more, printing equipment with a long service life or improper maintenance will cause the loss of small outlets due to changes in printing pressure. The use of a softer lining can reduce the loss of small points, but it will also cause further enlargement of the value of network points.

Assume now that only the changes in high-light and small dots are analyzed in the process of film-making, plate-making and printing: there is no change in the process of film output by high-gloss small dots, the small dot of 1% will disappear during the process of plate-making, and the printing process will also require Loss of 1% of small outlets. Obviously, the original 1% of small outlets were lost in the process of platemaking; 2% of the original site was reduced to 1% after the plate making process, but it was lost during the printing process. The smallest dot that can now be reproduced on the printed material is the original 3% dot. This is the end result of the production process consisting of these three processes. This result will not be improved by human intervention. This reflects the concept of process control: the process determines the product. In other words, what kind of process is selected and what kind of result it will have. Some people think that process control is to control the production process so as to achieve the desired results, simply the control process. In fact, the process is determined by the technical conditions of the equipment that make up the process. You can improve product quality by adjusting operations, selecting materials, improving the environment, and strengthening management, but this increase will not exceed the limits of the process itself.

Reasonable process design and management can give full play to the potential capabilities of the process and allow the product to obtain the best results that this process can produce in this process. This requires managers to fully understand the results achieved by all processes, to understand the components of product quality, analyze product features and process requirements and customer specific product requirements, select the appropriate workflow, and do a good job in process design.

For example, in the above hypothesis, if the technologist requests the computer process to set the white field of the image to 3% in advance based on the problems that may arise in the workflow, there will be no problem of high-light level loss due to printing and printing. In the same way, the technologist can design the black field and tone curve according to the characteristics of the dot expansion produced by this process, so as to avoid the loss of dark tone levels. Although this change may lead to a reduction in the contrast of the entire image layer, this result is more acceptable than the loss of the highlights and shadow levels. The role played by the color management system in the image processing process is exactly the same as the above process control principle. The color management system tests and analyzes the results of a workflow and compares the color changes of the color patches corresponding to the standard and test samples to obtain settings such as black and white fields, gray balance, and level curves. Order data.

For example, on a standard sample, dots with a color below 3% are not printed, and 85% with an Internet dot color no longer changes, indicating the range of color gradation and dot gain of the image that this process can produce. For another example, ink gray balance data can be obtained by comparing different colors of solid ink.
In addition to the normal operation of the process, another important factor in process control is process design. How to understand the product and customer requirements, how to choose the appropriate process, how to set the control data according to the established process, how to inspect and inspect the quality of the product and the final product acceptance in the process, all of which are inseparable from an advance Overall overall considerations and arrangements. Therefore, the prior process design is an indispensable and important part of process control. Some people say that the traditional printing process is a post-process correction process and cannot control product quality. In actual fact, in the traditional craftsmanship, experienced revision masters will pay close attention to the final printing results, analyze the changes in the original printing points after printing, and adopt copying, etching, etc. Network points for correction. The principle is the same as the above analysis, which is based on the possible changes in the post-process to correct the original network. Of course, this kind of experience can only be obtained after years of research and exploration. In the past, the data-based and standardized management that the printing plate-making industry strongly promoted was based on this principle. The modern computer image processing technology simplifies these operations into a simple operation process, and some operators do not seem to need to consider the tedious problems that may appear in the printing process. But in fact, these problems still exist. This is also the work that the process design must pay attention to.

All of the above analysis shows that the color characteristics of the printing equipment measured in the workflow are not only the printing machine, it is actually the color characteristics of the entire workflow. Different workflows produce different production results and therefore have different color characteristics. Scientific process management is based on product requirements to select the appropriate workflow, but also requires the use of matching color features for the image files produced by this workflow. This principle we all understand, but it feels difficult to implement.

Each large and medium-sized printing company will be equipped with multiple sets of plate-making equipment and printing equipment with different performance specifications. The application of plate-making and printing process will make the process changeable and difficult to control. For example, besides a production line consisting of an imagesetter, a plate-making machine, and a printing machine as mentioned above, it is assumed that a direct plate-making machine and a printing machine will be added, and these devices are all new. Formed another production line. If all the equipment on these two production lines are not used, it is a completely independent process. However, if an exchange occurs, the situation will be complicated. The plate making process consisting of the imagesetter and the plateetter corresponds to the two old and new printing processes; the direct platemaking machine also corresponds to two different printing devices and forms four different processes. The four different workflows obviously have different color characteristics.

For example, the work flow composed of the photo printing machine and the printing machine corresponding to the new printing equipment, due to the smaller value of the new printing equipment outlets, 1% of small outlets can be completely reproduced, but because 1% of the small outlets will be in the printing plate. The process is lost, so whitefield settings can start at 2%. However, if there is a work flow composed of a plate-making machine and a new printing device, it is possible to achieve a level-difference duplication. In the same way, even in the same process, the main material has changed, for example, from coated paper to offset paper, the color characteristics of its equipment will also change. From all the above analysis, it is best for printing companies, especially large and medium-sized enterprises, to purchase related equipment and allocate professionals to perform color characteristics testing. The equipment and equipment related to the test of color characteristics are not very expensive now, and the operation is very standardized and convenient. Equipped with dedicated personnel to do this work can calmly deal with various and even sudden changes.