The principle of choosing the number of screen lines for the color code

There are two basic principles to follow when choosing a screen number for a color code:

First, it is recommended that the number of screens on the color code should be the same as the number of screens used for the print job. This is mainly because the amount of dot gain will be affected by the number of screens. The higher the number of screens per inch, the larger the dot gain. The use of the same number of screens as the actual production to screen the color code can truly reflect the operating conditions of the printing press and is consistent with the halftone color separation method.

Second, it is recommended to use a slightly higher screen number than the print job. This principle is based on the fact that due to the finer number of screens, the color scales are more sensitive to changes in the printing process, and can be changed faster than actual production through dot gain and dot sharpening, so warnings can be exercised. People make necessary process adjustments before the image begins to change visually, reducing waste.
Whether or not a color code with a higher number of screen lines will be more sensitive to process changes, investigations on this issue show that this principle is correct in theory:

The number of screen lines between 133 lines per inch and 150 lines is the least sensitive to errors.

When measuring a color mark, the method used and the difference in measurement inherent in the use of the device are sufficient to override any differences in the number of color-coded screen lines.

There are currently two different views on the discussion of dot shapes. Some people think that color patches should use dot shapes that match the color separation film to provide the best correction. It has also been suggested to use round, square, and elliptical dots, each of which has its own advantages, and the difference in dot reproduction caused by dot shapes is small, and it is the same as the number of lines added to the measurement process. The change is much smaller than the change brought by copying or copying the color film.

The following method is recommended:

It is more important to consistently use the same number of color-coded screen lines than to correlate the number of color-coded screen lines with the number of screen lines actually produced. With the continuous accumulation of experience, operators, managers, etc., have begun to associate objective measurements with the appearance of images. Using color scales with different numbers of screens can hinder the understanding of these changes, introduce confusion, and increase the complexity of quality control.

Where possible, a color patch that matches the actual number of screen lines can be used. The number of screens of the color code is the same as the number of screens of the color separation sheet printed in parallel with it. When the measurement is performed, the visual appearance of the image can be easily associated with each part, and the confusion caused by the difference in the number of screen lines can be reduced. The smallest.

Color patches can use any dot shape, as long as the dot shape is consistent across all applied films and all objects that contain these patches.