Prepress plate quality control and its effect on printing results (1)

Editor's note: There are many factors affecting the quality of printed matter, but if problems arise during the prepress process, then even if the printed materials used are no better, the quality of the printing press is higher, and the binding is fine again, it will not be possible to produce qualified products. Prints. Prepress plate making is the precondition for producing qualified prints. If there is a problem in a certain part of the pre-press platemaking process, it may cause great troubles or even irreversible losses to the subsequent process.
Because the process of prepress plate making is very complicated and affects the quality of the final print product, we will discuss some of the quality control of several of the more important processes and how they will affect the quality of the printed matter.

First, the quality control of image scanning

The most basic job of printing is copying colors, which are often expressed through pictures. Image scanning is to convert the color information on a picture to a storable and editable digital signal through a scanning device, and then process these digital signals through application software such as image processing software and typesetting software. Therefore, whether or not the image can be accurately reproduced with high quality, that is, the information such as gradation, gradation, contrast, and saturation on the original as much as possible is a basic standard for measuring the quality of image scanning.

Printed manuscripts can be classified into reflective and transmissive manuscripts. Among them, reflective drafts are divided into photographs, prints, hand-drawn drafts, and drafts, etc.; transmissions are divided into positive and negative films. Since each type of manuscript has its own different characteristics, the characteristics of each manuscript must be fully taken into account when scanning the calibration.

Image scan quality evaluation:

(1) accurate calibration

Accurate calibration of the original document is the basis for the true restoration of the original, because it is related to the size of the entire image contrast and how much loss of highlights, dark tone and other issues. For example, for a transmitted original, if the contrast of the original is normal, the white field should be selected at a density of D=0.35—0.50; if the original is thin, the color amount needs to be increased, and the white field should generally be selected at a density of D=0.20. - 0.35; If the manuscript is more boring, it needs to be made brighter. The white field should generally be selected at a density of D = 0.60-1.80.

(2) Complete adjustment and high resolution

Tonality is the hierarchical structure of the entire picture. A complete tone can make the picture complete, because it is easy to lose the level in the darkest place and the brightest place, especially in the edge area of ​​a large area composed of pale white, this situation is more likely to occur. If the tone is the body of image color reproduction, then the clarity of the image can be said to be the soul of image reproduction. Sharpness can focus on vision: whether an image is clear is the most important factor in whether it can attract attention.

(3) faithful manuscripts, higher than manuscripts

When the manuscript has a rich gradation, strong contrast, and high saturation, it is sufficient to restore the gradation, contrast, and saturation of the original as accurately as possible during scanning. When the quality of the original is not very good, and sometimes there is even a clear cast color or low saturation, attention should be paid to the adjustment during scanning, so that the scanned image is more real and bright than the original.

Second, the graphic version of the quality control

(1) Consider the process

Graphic group edition is to combine the scanned image and the entered text according to the requirements of the customer. If the production requirements of the post-process are not fully taken into account in the process of group printing, all the printed products may be scrapped. For example, the bleeding level in general prints is 3mm, and the bleeding in the box is generally 5mm or 7mm. If you do not follow this standard at the time of group edition, you may increase the error rate of post-processes such as cutting, beer boxes, etc., resulting in unnecessary waste. Another problem is that when the cover is created, if the thickness of the paper used on the inner page and the binding method are not taken into consideration, it may cause the problem that the spine does not fit or the opened book cannot be placed on the table.

(2) Be careful and ask more questions

The group edition is a very complicated operation process. The operator must pay attention to the high concentration during the group edition. Otherwise, a small mistake may lead to large-scale rework. For example, during the production of an album for an auction, the operator forgot to replace the background image of the jade on the picture with a uniform black and white gradient background, resulting in the reprint of all 3,000 pictures. Sometimes the layout style provided by the customer is not very clear, or the salesman's label is not very accurate, which requires the operator to check more and ask more questions, and can't continue to make it until it is confirmed. Do not take it for granted, make your own claims or be afraid of trouble. Because this may cause more trouble.

(3) Increase training and improve rules and regulations

From the above example, it can be seen that the level of knowledge of the post-process knowledge of the printing press is very important for the group's printing staff. The printing company needs to regularly train the group's operating personnel for post-process knowledge. In addition, perfect rules and regulations are also essential to clarify responsibilities, reduce error rates, and increase accountability.