A new screening method to improve the quality of newspaper photos
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SandyP is not a FM screening technology, but a new AM screening technology.
Experiments show that SandyP screening technology solves most of the problems of newspaper traditional screening. As is well known, the typical problem of newspaper image reproduction is that the dots are severely enlarged, and there are visible rose spots and moiré. In the past, these problems were often considered tolerable, but as newspaper presses are increasingly used to print other commercial prints, these problems are becoming more and more annoying. Advertisers expect their full-color newspaper ads to have the same good image quality as their ads in magazines.
The fundamental problem in newspaper printing is that in order to ensure that newspapers are printed at high speeds, low-profile network cables are often used in printing. If you use a more detailed network cable, the dot gain will increase. If the method of reducing the gradation transfer curve is used to compensate for the dot gain, the photo will lose contrast and detail; at the same time, it will result in loss of dark detail in the darker region. In the three primary color printing, the dot angle causes an inaccurate mesh to adjust the dot to form a rose spot.
Further problems occur where the dots touch each other first and can see discontinuous tonal changes. In normal diagonal dot structures, this phenomenon typically occurs in the vicinity of the 50% dot value. This phenomenon can be attenuated when applying elliptical dots, but then it will occur in about 40% and 60%. In particular, when the portrait skin color is copied, a discontinuous jump may occur, and sometimes a moiré may occur.
SandyP Features
The SandyP solution has two characteristics in the dot structure: unlike the diagonal relationship of the traditional dot, the SandyP element is placed vertically and horizontally; the SandyP dot has no straight edges, but a spiral arrangement. This arrangement and dot shape means that the dots begin to touch each other only when the dot value is 90% or more. The distinctive dot structure and dot shape are the source of SandyP's advantages. It is said that spiral-type dots do not produce rose spots, which minimizes the moiré and increases the dots and spreads more evenly. After the experiment, the following four points were found.
The jump of the tonal value only occurs in the deep dark area (the dot value is above 90%), and in these places, the tone value jump is difficult to notice.
2 For different inks, different dot angles are still used, but no rose spots are produced.
3 The dots are not touched in the tonal range, which means that the dot gain can be more evenly distributed, and itself allows the application of finer screen lines. The number of screen lines of 40 lines/cm can be replaced by 36 lines/cm, or 48 lines/cm instead of 40 lines/cm.
4 Applying a spiral dot instead of a straight square dot means that virtually all the moiré can be avoided in the photo. In the advertisement of clothing, even the photos with the finest fiber can be copied in the newspaper.
In short, it can be said that SandyP makes the quality of newspaper photos improved in almost every respect.
Implementation
When deciding to implement the SandyP solution, the first step should be to analyze the existing conditions in the prepress and printing departments, with an ideal transfer curve for each customer's ink and paper.
The second step involves implementing and optimizing the process parameters in the RIP, and the dot gain of the press should be considered when setting the transfer curve. The dot gain of modern rotary presses generally varies between 18% and 22%, and different types of plates cause a wide range of variations, which must be considered.
The third step is to train prepress employees to optimize their application of image management software for SandyP's features.
The fourth step is to provide a long-term quality management process to periodically check for optimal replication.