Printing Quality Control--Subjective Evaluation (V)

Fifth, the evaluation of color products

Quality evaluation of color prints is subject to three constraints: first, the art and technical quality of the original; second, the proximity of the color prints to the originals; and third, the quality requirements for the reproduction of color prints as a commodity.

Prints cannot be separated from the originals, and the art and technical quality of various manuscripts are very different. Due to defects in color printing, printing methods and conditions, it is impossible to copy and restore originals faithfully and completely. Color copying is based on manuscripts and redistribution adjustments are made during copying.

It is the customers and readers who accept the printed matter. The quality of the printed matter is ultimately evaluated by the customer according to the quality standards of use. Due to the customer's subjective psychological requirements, cultural quality, purpose of use, etc., it is difficult to determine the quality evaluation standards for printed matters, especially for color prints. In the early days of color printing, subjective evaluations were mostly carried out by producers and recipients according to their own subjective wishes and requirements. Often, they could not obtain consistent opinions.

However, for color printing products, if there is always a subjective feeling and judgment of both the producer and the recipient to evaluate the quality, there is no objective product quality evaluation standard, so that the standardized printing production cannot be performed, and even the technology cannot be performed. Process and quality management. This is obviously not conducive to printing production, and it is not conducive to printing and modernization.

Regardless of the producer or user of the product, the color print screen is first accepted by people through intuitive vision, and the evaluation of the color print screen is first started by subjective evaluation.

The subjective evaluation of color prints is often based on the separation of color originals from the perspective of people. Cultural quality, purpose of use, plus their own psychological feelings, artistic requirements, etc., to subjectively evaluate color printing products. In fact, this has included the evaluation of the quality of color manuscript art and technology, and the comments on the degree of closeness of the color reproduction reproduction to the manuscript, and more and more variable commentary factors have been focused on the adjustment of manuscript reproduction. Commenting on whether the final printed product is close to meeting the subjective psychological artistic requirements of people.

With the gradual enrichment and systematization of basic theories and color theories of printing science and technology, we have systematically and comprehensively analyzed the subjective visual and psychological feelings of people. A large part of the quality indicators of color reproduction prints can be expressed or measured by objective quantities (physical quantities), and have been organically combined with the reproduction of prints. At the same time, it does not rule out people's subjective psychological requirements for color print screens. This aspect has also been incorporated into the adjustment factors and adjustment rules of color reproduction so that the color printing products can withstand the acceptance of the recipient in accordance with the general law of the comments. This means that the evaluation of color printing products can be summed up in some evaluation criteria combining subjective comments with objective measurement standards.

It is of great significance to establish an objective technical quality evaluation standard for printed products. For a printing factory, with an effective scale for judging copying and reproduction of products, it is easy to establish and design a data specification standard for printing production and implementation of technical process quality control. For the customer, the objective technical quality standards can not only satisfy people's subjective standards, but also can enrich and improve the specific content of objective technical quality standards through the customer feedback on product quality, so that the objective technology of print production Quality and people’s subjective evaluations are gradually harmonized.

Evaluating the quality of color products can generally include four main indicators:

1 tonal reproduction reproduction;
2 overall tone and color reproduction reproduction;
3 level definition of reproduction emphasizes reproduction;
4 The quality of various prints.

Among them, the latter two items are mostly subject to conditions such as the definition of the original document (or fine granularity), equipment performance, material properties, and copying technology, and the subjective adjustment factors added in the reproduction and reproduction process are also less. The two quality contents of printed products can establish objective technical measurement standards, but often subjective evaluations are used instead of objective evaluation.

For the first two items, due to the constraints of print reproduction and reproduction, material properties, and technical factors, the color and adjustment of the print screen cannot completely restore the original document, and can only be reproduced and reproduced in relative terms. There must be many and complex changes and subjective adjustment factors in the process of copying and adjustment. Even if the color manuscript is perfect, and as far as possible to faithfully reproduce the reproduction, although it can be compared with the manuscript by physical measurement of the printed matter, there are still some subjective evaluation factors that cannot be replaced by objective measurement standards. For example, if the picture is reproduced thicker or brighter, if the color is brighter or more realistic, whether or not there will be a better reproduction effect... This is often the case. Especially when there are certain defects and deficiencies in the manuscript itself, or when the manuscript needs to be changed and copied, the subjective adjustment concept in the reproduction and the subjective feelings of the observer are added. This requires the integration of people's subjective visual psychological requirements into the adjustment design and evaluation factors of the replicators, and then combined with the objective technical measurement standards of the reproduction and reproduction rules, in order to make a more practical and representative comprehensive evaluation. .