New trends in the development of modern screening technology
We are a big printing company in Shenzhen China . We offer all book publications, hardcover book printing, papercover book printing, hardcover notebook, sprial book printing, saddle stiching book printing, booklet printing,packaging box, calendars, all kinds of PVC, product brochures, notes, Children's book, stickers, all kinds of special paper color printing products, game cardand so on.
For more information please visit
http://www.joyful-printing.com. ENG only
http://www.joyful-printing.net
http://www.joyful-printing.org
email: info@joyful-printing.net
As we all know, the traditional screening method refers to the amplitude modulation (AM) screening method. However, the amplitude modulation screening method is prone to "moires", so people hope to find a screening method that can effectively avoid "clay". Therefore, the frequency modulation (FM) screening method came into being.
Color printing reproduction is C (cyan) M (product) Y (yellow) K (black) four-color printing. CMYK four-color ink printing is screened at a specific screen angle, resulting in a colored "rose pattern". Moreover, the color "clay" is very obvious in a continuous angle range, which destroys the effect of the image itself. The use of traditional screening methods often produces "clay". Why is there a "clay"? There are two reasons. First, if the angle of the screen between the color and the color is not suitable, or the overprinting is not accurate when printing, a "clay" will be produced. Second, sometimes the pattern in a particular background has a visual conflict with the screen line used for printing, and a "clay" is also generated. For example, when printing a textile pattern, the "latitude and longitude" line in the textile pattern interferes with the printing screen and interacts with each other to produce a "clay".
FM network (or random screening) means that the size of the dot is constant (generally smaller than the traditional halftone AM screen). The image is reproduced by changing the frequency of occurrence of the dot in the unit area. Tone and hierarchy. When the dots are brought together, a dark-tone area of the image is formed. When the dots are sparsely distributed, a bright region of the image is formed. Since there is no screen line number and screen angle in FM screening, there is no “clay” in color image printing. The result fundamentally solves the problem that the traditional screening method (amplitude screening method) easily forms a "clay pattern".
Advantages of FM screening: Initially, FM screening was mainly used in the printing of high-quality, fine prints, such as art albums. Because FM screens reproduce the details of fibers and jewels without "marriage". With the promotion of FM screening in printing production, it has been found that FM screening can effectively enhance the printing effect of low-resolution images. The detail reproduction effect of the screen output of the low-resolution image can be compared with the printing effect of the amplitude-added screen output of the higher screen line number, so the pre-press typesetting can use the lower resolution image. Because there is no screening angle, FM screening is not sensitive to overprinting. Thereby, the printing registration adjustment time and the preparation time of the adjustment are saved, the scrap rate of the adjustment machine is reduced, and the production efficiency of the printing enterprise is improved.
Disadvantages of FM screening: Although FM screening has many advantages in printing production, FM screening is not perfect. In the traditional phototypesetting machine printing production process, the printing staff spends a lot of time to ensure the consistency of the film transfer to the printing plate. The FM screening and the amplitude modulation screening are also very unstable to the chemical development process during the printing process. sensitive. The graininess printed in low contrast, flat screen and high light areas is very obvious, the dot enlargement is also serious and the plate density meter can not measure the optical density of the reliable frequency modulation screen. In order to obtain the ideal printing effect, it is necessary to use the dot to expand the compensation curve. To correct the output device; or print with the waterless offset process, because waterless offset can effectively reduce the dot gain.
The development trend of modern printing and screening technology
Modern printing and screening technology is in the ascendant, and new screening algorithms are emerging one after another. Traditional screening methods are also constantly developing and improving. However, the screening method can be divided into three categories: a new screening algorithm based on quadratic FM screening, a new high-definition screening algorithm based on AM screening and Hybrid Screening.
1. New screening algorithm based on quadratic FM screening
Secondary FM screening is generally divided into two steps. The first screening, mainly to determine the location of the network and use the network to aggregate to generate the image dark-adjusted area; the second screening, the application of an effective algorithm to generate a smooth, ordered image of the middle and bright areas, and adjust the size of the network and The shape thus controls the noise and chromatic aberration of the image after screening. The advantage of the secondary frequency modulation screening is that the tone transition is smooth, the image noise is small, and the dot gain is small. However, it is still difficult to adjust the color in printing.
2. New high definition screening algorithm based on AM screening
The development of FM screening technology has enabled people to obtain a moiré-free, detailed print. But now, some printing equipment suppliers have developed a number of new screening technologies based on traditional AM screening technology by combining the advantages of AM and FM. These new screening technologies innovatively use high-definition AM screening technology to allow low-resolution output to generate a much higher number of screen lines than the normal output. For example, a 360 lpi screen line screen can generate 2400 dpi resolution output through this screening algorithm. In addition, with the dot gain expansion curve correction output, very small dots can also be printed on the plate. Therefore, this screening technology allows the printing machine to easily print very good image detail effects, and is simpler to operate, while avoiding the drawback that FM screening can not adjust the color in printing.
So how does it avoid the appearance of "clay"? This new screening technology based on AM screening provides a more flexible screening angle setting. In addition to the standard offset screen angle settings, it also offers two new screening angle settings of 30O and 60O. In this way, the new high-definition screening algorithm based on AM screening can not only achieve better detail than FM screening, but also maintain the same process stability and color adjustment flexibility as the AM screening method.
3. Hybrid Screening
Recently, there has been a hybrid screening method, which includes both FM and AM, but it is different from traditional FM screening and AM screening.
In actual production, printers can use it flexibly according to their needs. Sometimes, we can use FM screening for the green, magenta and black versions, and traditional AM screening for the yellow version. Or in a color version, different content (such as images of different resolutions) are mixed using two screening methods. For example, in order to improve printability, FM screen is used for the high-gloss area of the image, and AM is used for the mid-tone adjustment. This is because in the middle adjustment, the dot generated by the AM screening is small and the edge of the dot is clear. However, in the high-light area, the dots are small and more suitable for FM screening. This hybrid screening method is ideal for flexographic printing and offset printing processes. Another technique called high-density screening technology is also beginning to be applied to the flexo process. We know that the general flexo density is not high enough, and this The technology can help flexo produce a higher density in the field than the usual screening method. It is actually to replace the dot of the dark-adjusted area with a thin line, which can improve the printing reproduction effect of the real area, and improve the thickness of the printing ink layer and the saturation of the color.
When we moved from electrical extensions to DTP (Color Desktop Publishing System), and now the popular CTP direct platemaking system, the screening method has gradually diversified. However, whether it is based on the AM screening method or the FM screening method, the new screening technology has improved the detail reproduction ability of the image to varying degrees. With the update of the screening algorithm and the improvement of printability, we believe that in the near future, we will see a new generation of screening algorithms with clear, no moiré, good printability and more vivid colors.