The advent of the CTP era has not only changed the efficiency and cost of printing production, but also has more flexible means of quality control than traditional CTF printing processes, such as: standardization of level hierarchy and more precise control of data control. The restoration is more stable, the gray balance control is more accurate, the definition control is simpler, the color of different printing conditions is easier to achieve, the dot reduction is easier, the application of high-end screening technology is more popular, etc. It can be said that the process technology has revolutionized. Change.
With the popularization of CTP printing technology, hybrid screening and secondary frequency modulation screening technology are widely used, but they all have high-definition characteristics, so there are specific requirements for pre-press, plate-making and printing processes, otherwise the final printing The effect of the product is difficult to achieve the expected value, and even if it is not good, some aspects are not as good as the traditional 200lpi amplitude modulation screening. Therefore, if users use high-end screening, the following matters must be noted in production:
1, the quality of the image
The quality requires that the tone level of the image is normal, color saturation and high definition, and it is necessary to avoid the use of low-resolution images with insufficient information, loss of tone level and inferior images with serious level, abnormal color and sharpness, etc. . Because if the image quality is flawed, the hybrid screening and the secondary FM screening will not only magnify the defects of the 8-bit continuous tone image, but also the influence of the variable factors in the post-production and printing process. The result of the cumulative error results in a worse quality print.
2, the accuracy of the image
In terms of accuracy, the amount of image information is sufficient, and the resolution is 300 dpi or more to ensure the accuracy of printing. The early screening technology required "image resolution = screen factor × screen line number, screen factor = 1.5 ~ 2, and the current Founder new network technology has a unique optimization of the level, so there is no need to be limited to this formula That is, 300lpi screening does not require the image resolution to be 450dpi to 600dpi.
3, the type of image
The biggest feature of hybrid screening and secondary FM screening technology is to highlight the subtle level of the image, which means that the dot technology is known for its image exquisiteness, texture and clarity! For the color of the image, the color gamut space of the mixed screen printing is not much different from the traditional 200dpi printing. The secondary frequency modulation screen printing gamut space is larger than the traditional 200dpi color gamut space, but from the visual observation and psychological impression evaluation of the printed products. From the above point of view, the performance of the secondary FM screening in the color can not detonate the observer's eye, the impact is not very obvious, I guess that perhaps under a certain range of narrow conditions can show this advantage, I hope in the future Can be found in practice. As for image contrast and appearance, as long as the color management in the CTP printing process can achieve the traditional 200lpi and hybrid screen printing consistent.
Therefore, in order to give full play to the characteristics of hybrid screening and secondary FM screening technology, the selection of pre-press image types in printing production needs to be accurately positioned, that is, not all jobs can be printed with high-end screening. The precautions are as follows:
(1) In general, the image with rich dark tone and uniform distribution of high light and light is optimal. Such as: clothes, leather shoes and wooden doors and other strong texture objects; and high-light bright and rich, but also a large area of ​​flat nets and gradients of the original manuscript need to be used cautiously, because hybrid screening and secondary FM screening can Reproduce the complete tone level of these images, but due to the influence of post-production and printing factors, the reduction of small dots is not as easy as the traditional 200dpi. Microscopically, some dots are restored, some dots are poorly reproduced, some dots are full of ink, and some dots are The ink color is not real, and finally the macroscopic reflection on the printed product is that the flat net vision is uneven and rough;
(2) The image of the person (especially the close-up of the face) requires higher quality of the original picture, especially the smooth transition of the tone level. Otherwise, the transition may be caused by the influence of the original, the plate making and the printing process, and the face is not soft;
(3) The landscape image (especially the sky close-up) also needs to be smoothed by the original pattern level transition. Otherwise, the effect may be caused by the influence of the original and the plate making process, and the grain is heavy;
(4) For the originals of Chinese painting, oil painting, gouache and watercolor painting, because the general author paints on the rough paper with outstanding texture, although the mixed screening and the secondary FM network are small, there is a disadvantage of incomplete restoration of the dot in the plate making and printing. However, there is no serious problem with these manuscripts, and sometimes it is an advantage. Therefore, it is relatively ideal to print such manuscripts by using hybrid screening and secondary frequency modulation screening technology;
(5) For newspaper printing, hybrid screening and secondary frequency modulation screening technology can be fully used in CTP printing process. These screening methods will make the image exquisite, texture and clarity more prominent, in line with the characteristics of newspaper printing. And requirements. Perhaps some users are worried that high-precision screening will have a dark level of leveling and blurring when printing from 100dpi to 120dpi in traditional newspaper printing. It is understandable that this is true in the CTF printing process. The problem, but it can be solved by color management in the CTP printing process.
4, plate making process
Hybrid screening and secondary FM screening technology are high-precision screening. Small outlets are sensitive to CTP working conditions, so the process control in the publishing process needs to be stricter than ordinary AM. If the streak phenomenon sometimes occurs in the case of poor publishing, and the uniformity and stability of the dot are fluctuated greatly, the publishing state needs to be strictly regulated for such a net, otherwise the printed product will have a net, texture and roughness. Quality issues.
5, printing process
Hybrid screening and secondary FM screening technology are high-precision screening, and small outlets are also sensitive to the printing work status, so the process control in the printing process is more strict than the ordinary amplitude modulation. If the dots in the printing are dark and smooth, the ink balance, the rubber surface and the printing pressure are in a good and stable state, then the dot reproduction can ensure its reproducibility and stability, otherwise it will There are quality problems such as uneven transitional transition, flat mesh unevenness and large color fluctuations, resulting in high-end screening printing that is not as effective as traditional AM-format screening.
With the introduction of CTP, the application of high-end screening technology to improve printing quality has become the goal and desire of users. The author believes that as long as you deeply understand the characteristics of these special screening technologies, you can make full use of its advantages and avoid the preparation of its shortcomings. Carrying out the "quality image and precision image", "appropriate image type" and "good publishing, printing status" specifications, I believe that the printing effect can be separated from the traditional printing, resulting in good market feedback!
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