From what aspects should the quality of digital printing be evaluated?

In the process of commercial transactions, it is particularly important to correctly evaluate the quality of digital printing. As we all know, the complexity of color printing process often requires more than a dozen steps to complete a digital printing, which involves companies, staff and so on. Different environments and times have different evaluation methods or requirements for digital printing. Therefore, in this process, it is necessary to formulate some norms and corresponding observation conditions.

Therefore, only by limiting external factors, such as the environment, can we make a subjective evaluation of digital printing, be fair and objective, and reduce disputes caused by the environment. Therefore, a standard lighting environment and a standard light source are necessary.

Chromatic aberration of digital printing

Color difference can be divided into (1) original color difference: the purpose of printing reproduction is to reproduce the color level of the original, and the highest standard of subjective evaluation is to make digital printing indistinguishable from the original. (2) Color difference in the same batch: refers to the color difference between different sheets of the same batch of products in the same hue area and in the same position. (3) Color difference between different batches of the same product: refers to the color error between different batches of the same product. If the colors of each batch of printed matter are slightly different, when put together, customers will feel that these goods are new and old, and even doubt whether their internal quality will be as unstable as their appearance, thus generating distrust of the goods, which will naturally cause manufacturers' dissatisfaction with the quality of the products of the printing house.

As customers and printers, we hope that the value of this color error should be zero. However, due to various conditions in actual production, it is impossible to completely eliminate the color difference. Only by strengthening the quality control of each link can the color quality difference of products be controlled within the specified color difference standard. Color difference refers to the color difference between digital printing and the manuscript or proof acceptable to customers.

Whether in the process of printing or when checking the quality after printing, printing operators or quality inspectors should always rely on their own feelings and experiences to evaluate the color quality of printed products based on the fidelity and fidelity of reproduction. The fidelity of reproduction refers to the degree to which digital printing reproduces the color level of the original. Digital printing is a kind of reproduction. In the whole process of color reproduction from prepress to printing, the manuscript is the basis of our work, and the purpose of printing reproduction is to copy the color level of the manuscript. Making digital printing and manuscript indistinguishable is the highest standard of subjective evaluation.

In the absence of manuscripts to compare, the color quality of digital printing is related to the sense of reality, that is, it is required to meet the memory color of most people. Most people have preconceived habits about common objects. If the color of the subject in digital printing is different from the color of the object, this digital printing cannot be called a high-quality copy. In a word, the subjective evaluation standard of digital printing color quality is to reproduce the truth, nature and harmony, which sometimes changes slightly with the intention of customers or the use of products.

Definition of manuscripts Most of the manuscripts in previous years came from photographic slides, photos and hand-painted color manuscripts. In the process of color separation and manuscript typing, if it can be close to the manuscript, it is regarded as effective color reproduction. As for printing, it is based on the manuscript approved by the guests. As long as it can be followed up to 90%, it is generally qualified.

However, in today's computer age, there are more definitions of manuscripts. For example, if a guest sees a satisfactory color or a printed manuscript sample on the computer screen, it is considered a manuscript. No matter what kind of manuscript it is, the recorded or displayed color may not be displayed under general printing conditions, because each color reproduction system has its color gamut limitation. In the production process, the object of the photographer is the manuscript, the color separation plate maker takes the photographed photos as the manuscript, and the printer takes typing as the color following goal.

The objective evaluation of digital printing color quality is to calculate the result of subjective evaluation by statistical means, and then convert it into corresponding physical quantities as the objective evaluation standard. In this way, the influence of human factors in evaluation can be eliminated, and the color quality of various digital printed matter can be evaluated fairly with standardized and unified standards, which will eventually make it more in line with the subjective evaluation standards of most people. The objective evaluation method mainly uses specific measuring instruments and tools to measure some standard elements printed together with digital printed images. Only through measurement can the automatic control of digital printing quality become possible to some extent.

Color quality and production control

In order to produce high-quality color digital printing, it is necessary to strengthen the quality control in the production process, and the quality control mainly depends on the objective evaluation standard of products, that is, to formulate a set of strict data specifications and objectively measure and evaluate the color quality of digital printing with the help of various instruments.

The purpose of color control management is to improve the small gap between manuscripts, proofs and products. In the process of printing, if we can spot-check digital printing at any time, we can find problems through biased data and find out the reasons in time, so as to correct the problems and ensure the reproduction quality of digital printing. In addition to using density as a parameter to reflect the color quality of digital printing, CIELab chromaticity value of color should be popularized as a parameter to detect the quality of digital printing.

Every link should be managed by data, and every step should be detected by testing tools, otherwise there will be many mistakes. Nowadays, with the continuous progress of technology, the means of color control in printing have been further developed, and the brand-new color management system makes printing color control more convenient and effective.