The evolution of dot lines: painted stone plate to computer plate

A hundred percent of a color ink can only be printed on the printed material, which is a well-known law. However, if various means are used to decompose into different density dots on the printing plate, different shades can be formed on the object to be printed, and a variety of shades can be achieved.

Back in the early 1920s, the original lithographic plates were made with specially crafted small pen tips and black ink. They were hand-painted with different shades to meet the requirements. At the time, they were called painted stone plates. Subsequently, it progressed to films made of different densities, pressed out of concave and convex dots, and wooden frames (called "offsets") around the shed as tools. Black ink was applied on the sheds. After that, according to the requirements of different shades, they were imprinted in India. On the stone, the ergonomics at the large area are greatly improved, and when the number of lines is about 60 lines per inch. In the 30's, photo-engraving began with the use of glass screens imported from Japan. During photography, the film was affixed with dots, from the initial 100 lines, 120 lines, and 133 lines to 150 lines. In 1965, the glass screen was changed to a magenta contact screen, and the yellow filter was used to adjust its latitude so as to adapt to the density contrast of continuous color separation. Afterwards, the gray contact screens, which were later improved to different tones, were produced and supplied by the Beijing Institute of Printing Technology and the Shanghai Institute of Printing Technology. The majority of them were used for offset printing with 150 lines. In 1973, Beijing Xinhua Plant and Shanghai Yinye Plant first introduced the German-made Haier DC-300A electronic color separation machine, which still uses screen mesh netting. When the DC-300B is to be introduced, the number of outlets is slightly different, ie 150 lines for C, M, and Y, and 225 and Y for the K version. Until the early 1980s, the electronic color separation machine was improved from analog to digital, and its dot line number also progressed to 175 lines, which remained basically unchanged in the past 20 years.

Everyone in the industry knows that the density of dot lines is also called the thickness, which is related to the resolution and gradation reduction capability and the degree of refinement of printed products. However, it must also be based on the corresponding conditions for printing. Recalling that in 1959 it was an exhibitor at the East Leipzig International Book Fair, the Shanghai leadership put forward high requirements for the making of the “Shanghai Museum Art Collection”. Therefore, 200 network lines were used as an exception, which was to overcome many difficult conditions at the time. This also won the only gold copy award of the plenum. However, with the so-called "Great Leap Forward," the nation's printing and graphic arts industry also blew up the "high net line" style that is not viewed by customers. At that time, the competition produced small samples. From the 300 line, the 500 line, and even the 800 line, it was called the "release satellite" in the printing industry. The production process will be the first to shoot a 150-line screen into a 30-inch-high Yang network, use it to shrink to 7.5 inches of the Yin network, and then copy the Chengyang network, into a 600-line network of original. However, the finest gold steel sand used for the zinc skin plate was not fine enough and was pulverized with pumice powder for grinding. It was barely able to produce rough samples and could not be printed on the machine, completely contrary to the scientific laws of objective reality. I have also participated in the matter. I am ignorant and obedient. I just deceive myself!

In the computer-to-platemaking days, the vast majority still use 175 lines, but scanning colorimeters (or electric extension scanning systems) can combine up to 200 lines and even 300 with 3,600 dpi or more internal drum laser imagesetters. Lines can also be sent to the FM network (also known as the sand mesh point that is the same as a single network point at the finest point of the 300 line, depending on density or evacuation to form shades, because there is no angle, so no moire). Due to the current high-performance photographic film, high resolution PS plate, high adaptability ink, excellent expressive paper, imported precision proofing machine, and four-color printing machine, the acceptable number of outlets has been More than 175 lines needed. Recently, we have also seen that some of the fine prints printed in Shenzhen have adopted 200 lines, and the recently used black and white photos from the “Reference News” printed on newsprint have also used 175 lines. Therefore, we should not rest on our laurels and we should be able to increase the number of dot lines. . Although backtracking Shanghai is also occasional, it is not universal. The hacking platemaking process should be subject to the combination of subjective requirements and macroscopic possibilities. For this reason, when we encounter the production of exquisite products and the manuscript is more ideal, at present, it seems that the use of 300 lines does not seem to be necessary, and the line of thought adopts 200 lines, which is neither aggressive nor conservative. More beautiful. If you promote the CTP process in the future, you can adapt it.

Source of information: pack.cn