New Screening Method Improves Photo Quality of Newspapers

Kurt K. Wolf, an internationally renowned industry expert, recently introduced a new screening method, Sandy P Screening Technology, which can improve the quality of newspaper photos. Sandy P is not FM screening technology, but a new AM screening technology. In Germany, the United States, Ireland and Austria, four newspapers have used it.

origin

Sandy P's screening technology was launched two years ago by Sandy Screen, a Swiss company. Experiments show that Sandy P screening technology solves most of the problems of the traditional screening of newspapers.

As we all know, the typical problem with copying newspaper images is that dot gains are serious and there are visible rose spots and moire patterns. In the past, these issues were often considered to be tolerable, but these issues are increasingly annoying because of the increasing number of newspaper presses used to print other commercial prints. Advertisers expect their full-color newspaper ads to have the same good image quality as their magazine ads.

The fundamental problem in the printing of newspapers is that in order to ensure that newspapers are printed at a high speed, a low-cost screen line is often used in printing. If you use a more elaborate network cable, dot gain will increase. If the dot gain is compensated by reducing the tone transfer curve, the picture loses contrast and detail; at the same time, it also results in the loss of dark tone details in the darker areas. In trichromatic printing, dot angles can cause inaccurate dot formations in rose dots.

Further problems occur where the outlets first touch each other, and can see discrete color changes. In the normal diagonal dot structure, this phenomenon usually occurs in the vicinity of the 50% dot value. This phenomenon can be reduced when elliptical dots are used, but then it still occurs in about 40% and 60% of places. Especially in the reproduction of human skin, discontinuous jumps may occur, and moire sometimes occurs.

Sandy P Features

Sandy P's solution has two characteristics in its dot structure: Sandy P elements are vertically and horizontally arranged differently from the diagonal relationship of traditional dots; Sandy P dots do not have any straight edges, but appear spirally. This arrangement and dot shape mean that the dots start touching each other only when the dot value is more than 90%. The characteristics of Sandy P are the source of characteristic dot structure and dot shape. Allegedly, spiral spots do not produce rose spots, minimizing moiré, and allowing dots to grow and spread more evenly. After the experiment, the following 4 points were found.

1 The hue value jump only occurs in the dark shadow zone (over 90% of the dot value). In these places, hue jumps are difficult to notice.

2 For different inks, different dot angles are still used, but no rose spots are produced.

3 Dots do not touch within the tonal range, which means that the dot gain can be more evenly distributed, and it also allows the application of finer screen numbers. A 40-line/cm screen can replace 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 moire can be avoided in the photo. In the adverts of clothes, even the finest fiber photos can be copied in the newspaper.

In short, it can be said that Sandy P has improved the quality of newspaper photos in almost every aspect.

Implementation

When deciding to implement the Sandy P solution, the first step should be to analyze the existing conditions in the prepress and printing departments, and to provide each customer with the ideal transfer curve for ink and paper.

The second step involves the implementation and optimization of process parameters in RIP. The increase in the dots of the printer should be considered when setting the transfer curve. The dot enlargement of modern rotary presses generally varies from 18% to 22%, and the range of changes caused by different types of printing plates is wider. This must be considered.

The third step is to characterize Sandy P and train prepress employees to optimize their use of image management software.

The fourth step is to provide a long-term quality management program to periodically check for optimal replication.