First, aesthetic factors
Because print is a visual product after all, when people evaluate the quality of printed matter, the first impression is the aesthetic effect of printed matter.
The esthetic effect of prints is mainly related to the design level of craftsmen. Font selection, color design, art patterns, image placement, layout layout, and selection of paper and ink are all related to the aesthetics of the print. A good design can make printed products show good aesthetic characteristics, but it is difficult to describe the fineness of the design by quantity. Sometimes, "good" design actually does not meet the rules of typesetting, color combination, image synthesis and so on. Some people think that a bad design may be appropriate when used on the cover of some albums, but it is inappropriate for high-end cosmetics ads. Also, using current standards to measure the design of previous years, most of them are out of date. This means that there is a question of "fashionable" in image design. From this we can see that the aesthetics of print quality is actually a reflection of the imagination and creativity of designers. An excellent designer should be familiar with aesthetic design guidelines, and should know the technical constraints in printing materials, inks, and printing processes in order to produce excellent aesthetic results.
Second, technical factors
After the format design of the printed manuscript is completed and the printing method, ink, and substrate are determined, it is technical factors that can affect the print quality. Technical factors are the factors that influence the quality of printed products in various processes of printing production. In the limited range of platemaking, printing equipment, and printed materials, as far as possible, faithfully reproduce the designed content.
The technical characteristics of print quality include image clarity, color and scale reproduction, gloss finish, and texture. Among these characteristic factors, some of them can be expressed in terms of quantity, such as color and coordination. In the various processes of the replication process, people can control these factors; some technical factors cannot be expressed in numbers, but they can be described in terms of language. . For example, in order to obtain the best print quality, the possibility of moiré must be minimized. This is in the form of a language description; again, the gloss characteristics may vary depending on the end use, in order to improve the text print. Readability requires the use of low-gloss paper, but in order to achieve the best contrast in the reproduction of photographic originals, high-gloss paper is also required.
Third, consistency factors
The question of the consistency factor is: How much change can be allowed between individual sheets? This is a problem with the quality stability during the printing process. As the number of prints increases, the printing time increases accordingly. During this time, the addition of various variable factors will inevitably be reflected in the quality of printing. In addition, due to problems with the printing plate's resistance to printing force, it is sometimes necessary to replace the plate halfway, or it may be due to paper. The failures of blankets and printing presses have to be shut down in the middle, so that the original relationship between ink and ink is disturbed. Once it is reprinted, its print quality cannot be consistent with that of the first printing.
With regard to the changes between printed pages, the following aspects should be explained:
First, visual resolving power. For example: In the standard observation distance, when the number of screen lines is 150 lines/inch, the maximum allowable value for registration change is 0.05mm. Beyond this range, changes in the image can be visually observed.
Second, the intrinsic characteristics of the production equipment itself produce uncontrollable image variations. For example, the existing ink-transmitting mechanism of offset or embossing machine can not guarantee the consistent density from front to back on the printed sheet, and the density variation on the same printed sheet can reach 0.15.
Third, the allowable deviation limit. This needs to be decided according to the type of product and the customer's requirements. For example, newspapers can have a large change in color while the colors of cosmetics or food packaging products do not allow large color differences.