Summary:This article clarifies some common issues and misconceptions regarding color management in printing, outlines the process steps of color management, and aims to reduce preparation time, minimize waste, and improve production efficiency.
Keywords:Color management, color standards, color measurement, color difference, density
In daily work, I have encountered many printing companies with complex feelings about color management, ranging from those who love it and hate it, to those who praise it excessively and those who simply don't understand it. So, why is there such a wide range of opinions? Next, let's discuss some common misconceptions about color management:
1. Factory A reported that the digital files provided before printing did not match the colors on the printed sheets, and it was impossible to achieve the desired print effect after printing. A revision was required. Upon investigation, it was found that the digital printer used for pre-press was modified for alternative ink printing. The paper used for printing was ordinary printing paper, and the ink color was unstable in each batch. The print heads frequently clogged, and the heating temperature was unstable. The printing paper varied in color. Given these numerous unstable factors, is it possible to achieve consistent results?
2. The B factory reported the same printing file, but the copies were not matching the colors. They needed to revise the file. After investigation, it was found that their printing platemaking machine had not been cleaned or replaced with fresh developing solution for one month, and the developing temperature was unstable. Furthermore, they were not using any measuring instruments to monitor whether the printing plate's mesh count met the required standards, and they were not monitoring this parameter at all.
3. The production at Plant C is very busy, and there is no time for maintenance of the printing presses. The presses are constantly operating. This results in inconsistent print quality, large color variations between the top and bottom of the printing plate, a large and unstable dot gain, and overall poor print results.
The primary goal of color management is to utilize color management tools to reduce printing preparation time, minimize waste, and improve production efficiency.
However, despite significant investment of both manpower and resources, the results were not as expected and fell far short of the desired outcomes. What were the reasons for this?
Often, our understanding of color management is limited. Some believe that installing a digital proofing system from a printing press is sufficient for color management. Others believe that performing CIP3/4 line connection during pre-press printing is sufficient for color management. Still others believe that correcting printing curves is sufficient for color management...
In reality, color management is a comprehensive system that requires close collaboration between pre-press and printing operations. Through the use of various testing instruments and color management software, a color standard is established and maintained regularly to achieve the desired results.
As shown in the diagram above, it is a flowchart summarizing the color management process, which I have compiled.
Next, we will examine in detail:
01
The top of the image represents the standard color specifications, which can be the factory's custom color standard, the customer's desired standard, or an international standard such as ISO 12647-2. The subsequent color control workflow is centered around this target standard.
02
once the target is determined, the process begins with pre-press activities. First, a soft proofing is performed to match the printing standards. This involves calibrating a professional display, loading ICC profiles for color correction, and ensuring that the colors displayed on the screen match the printing color standards.
03
The digital proofing system consists of a wide-gamut printer, color management software, and color detection instruments. The printer prints color swatches such as TC1617, and color detection instruments such as i1iO (as shown in the figure) are used to detect the color of the swatches. The results are fed back to the color management software, where they are compared with the target printing color. If the color difference exceeds the tolerance range, the software adjusts the color proportions accordingly. This process is repeated until the digital proofing matches the printing standard.
04
Whether it is hand-applied samples or digital samples, regular testing and adjustments are necessary to ensure consistent color and adherence to printing standards. If the color cannot meet the required specifications or remains unstable, consider adjusting the printing conditions to achieve the desired color.
05
After soft and digital proofs meet the required standards, we need to perform inspection of the printing plates. Please note the following two points: firstly, standardize the pre-press production process, including the layout of the printing plate curves, to ensure that the plate's dot errors are within the tolerance range, such as not exceeding 0.5%. Secondly, conduct regular inspections to ensure that each printing plate meets the standards. If any issues are found, they should be addressed and resolved promptly.
06
Next is the standardization management of printing machines.
First, the standardized management of the ink-releasing liquid: parameters such as pH value/electrical conductivity/alcohol ratio/water tank temperature. Second, the standardization of the ink delivery system: including the status of water, ink roller, water-ink roller pressure, and bearing status, as well as ink parameters. Third, the standardization of the rubber cloth parameters: including the elasticity, hardness, and changes in resilience of the rubber cloth after prolonged use. This includes the use of either specialized or general paper under the rubber cloth. The rubber cloth's surface roughness/hardness (too high can cause "bulging" and "ridges" during printing, while too low can cause distortion of images), thickness loss rate, and printing durability should also be standardized. Finally, other functions, such as registration function, ink slot and ink key function, water tank cooling and ink-releasing liquid circulation replenishment function, etc., must also be standardized and compliant.
only after implementing standardized management and quantifiable metrics within the printing machine itself, and achieving the required standards, can the next stage of printing standard matching be carried out, which will then be meaningful.
07
Next, adjust the printing standards of the printing machine.
We first test the color accuracy of CMYK/RGB using print tests and other methods to ensure that the color difference meets the standards. If the color difference is not within the acceptable range, we need to consider replacing the ink and/or paper. Secondly, we obtain the correct screen expansion and gray balance plate curve to recreate the plate and achieve the correct screen expansion and gray balance. Finally, by coordinating the printing press, color management software, and color measurement instruments, we ensure that the colors printed by the printing press match the target colors. We record the standard density to obtain the ICC profile for the printing press.
08
The first printing machine has completed the standard printing process. Next, we will perform horizontal operation on the second and third machines, following the same method as the first machine. However, please note the following:
1. Ensure that the mesh points of each printing press are appropriately expanded and that the corresponding printing plate curves for accurate ink balance are properly managed, without any ambiguity or misinterpretation.
Two. Clearly and correctly manage the pre-press machine's halftone correction curves and the printing machine's halftone expansion and gray balance plate curves, understand their functions, and avoid using them incorrectly.
09
Maintain consistent printing conditions: This includes printing materials such as inks, fountain solutions, and printing plates; as well as printing processes and methods, such as color sequences. Changes in printing conditions during the printing process (including pre-printing) will affect the success of color management.
10
Similar to the pre-press stage, after matching the printing machine to the desired printing standards, regular maintenance of the machine is essential. This should be done according to standardized management practices, ensuring that parameters meet the required specifications and that quantitative monitoring is performed. Regular matching of the printing machine to the desired printing standards is also necessary, including correcting any deviations and verifying the match against the standards. This ensures consistent printing quality.
11
based on this, to improve production efficiency, we implement CIP3/4 connection and generate pre-ink curves according to printing standards. This is the most effective way to achieve optimal ink distribution. Additionally, scanning and closed-loop systems (as shown in the figure) can be installed: The scanning system detects the difference between the current color and the target parameters, while the closed-loop system automatically adjusts the printing machine's ink keys to quickly achieve the target color. This reduces paper waste, improves production efficiency, and enhances color quality.
Summary
In summary, we hope everyone can implement a comprehensive color management system, ensuring that all aspects are interconnected to form an efficient and accurate color management loop. This will enable us to improve color quality, reduce waste of paper, ink, and labor, and ultimately enhance operational efficiency.