KurtK.Wolf, an internationally renowned industry expert, recently introduced a new screening method—SandyP screening technology that can improve the quality of newspaper photos. SandyP is not a FM screening technology, but a new AM screening technology. It has been used by four newspapers in Germany, the United States, Ireland and Austria.
origin
SandyP screen technology was launched by a Swiss company SandyScreen two years ago. Experiments show that SandyP screening technology solves most of the problems of traditional newspaper screening. As we all know, the typical problem of newspaper image reproduction is that the dots increase seriously, there are visible rose spots and moire. In the past, these problems were often considered tolerable, but because of the increasing use of newspaper printers to print other commercial prints, these problems are becoming more annoying. Advertisers expect their full-color newspaper ads to have the same good image quality as their magazine ads.
The fundamental problem in newspaper printing is that in order to ensure that newspapers are printed at high speeds, low-level screens are often used in printing. If you use a more elaborate network cable, the increase in dots will increase. If the method of reducing the tone transfer curve is used to compensate for the increase of the dots, the photo will lose contrast and details; at the same time, it will also cause the loss of dark details in the darker areas. In three-primary color printing, the dot angle will cause inaccurate mesh adjustment dots to form rose spots.
A further problem occurs where the dots first touch each other, and discontinuous tone changes can be seen. In a normal diagonal dot structure, this phenomenon usually occurs in the vicinity of the 50% dot value. When applying elliptical dots, this phenomenon can be reduced, but then it will happen at about 40% and 60%. Especially when copying the skin color of portraits, there will be discontinuous jumps and sometimes moire.
SandyP features
The SandyP solution has two characteristics in the dot structure: unlike the diagonal relationship of traditional dots, SandyP elements are placed vertically and horizontally; the contour of SandyP dots does not have any straight edges, but presents a spiral arrangement. This arrangement and the shape of the dots mean that the dots only start to contact each other when the dot value is above 90%. The unique dot structure and dot shape are the source of SandyP's advantages. It is said that spiral dots do not produce rose spots, can minimize moire, and make dots increase and spread out more evenly. Through experiments, the following 4 points were found.
â‘ The jump of tone value only occurs in the dark and dark tone area (the dot value is above 90%), and in these places, the jump of tone value is difficult to be noticed.
â‘¡For different inks, different dot angles are still used, but no rose spots are produced.
â‘¢ The dots do not touch in the range of tones, which means that the dots increase can be more evenly distributed, and it also allows the application of finer screen lines. The number of screen wires of 40 lines / cm can replace 36 lines / cm, or 48 lines / cm instead of 40 lines / cm.
â‘£ The use of spiral dots instead of straight-sided square dots means that virtually all moire can be avoided in the photo. In clothing advertisements, even photos of the finest fibers can be reproduced in newspapers.
In short, it can be said that SandyP has improved the quality of newspaper photos in almost every aspect.
Implement
When deciding to implement the SandyP solution, the first step should be to analyze the existing conditions in the prepress and printing departments, and to equip each customer's ink and paper with an ideal transfer curve.
The second step involves the realization and optimization of process parameters in RIP. The increase in the dots of the printing press should be considered when setting the transfer curve. The dot gain of modern rotary printing machines generally varies between 18% and 22%, and the wide range of changes caused by different types of printing plates must be considered.
The third step is to train the pre-press staff in accordance with the characteristics of SandyP to optimize their application of image management software.
The fourth step is to provide a long-term quality management program to periodically check the best replication.
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