The development of printing technology for half a century 1.2

Section 2 Development of Photographic Technology

The printing process can be divided into three phases: photolithography, printing, and postpress processing. Among them, the technology is the most complex, and the greatest impact on the development of printing technology is the photolithography technology. Photographic platemaking can be further divided into two processes: photo first and then plate making. Photographing begins with the manuscript, and negative or positive film negatives are photographed on the plate making camera; plate making uses negative or positive negative film to overturn the printing plate.

Prior to the 1950s, photography equipment was only available in printing facilities in major cities such as Shanghai, Tianjin, Beijing, and Changchun. In the mainland and some remote areas, many printing plants had neither photographic equipment nor photographic techniques. . There is a photo-printing printing plant, and most of the cameras used are small hand-held cameras with a wooden frame structure. The photosensitive material used is silver iodide gel (also known as Luodian). This photographic process has been used since the photography was introduced more than 100 years ago, without much change.

Plate-making film "dry-generation wet" I. Homemade plate-making film "dry-generation-wet"

Among the materials required for photography, the most important one is a photosensitive material. Prior to the fifties, the photographic material used for photography was a glass plate as a substrate, and an iodide-contaminated cotton solution (commonly known as Luodian) was uniformly coated on a glass plate, and then placed in silver nitrate. Solution plate. The iodide in the cotton gel reacts with silver nitrate to produce silver iodide with photosensitivity. Then dampen and put the cotton nitrate silver nitrate glass plate on the camera and take the exposure immediately. The name "wet version" comes from this.

Wet plate is also called wet film and it is a color-blind film. Photosensitivity and color sensitivity are poor. In order to shorten the exposure time as much as possible, a carbon lamp with high power is used as a light source on the camera.

After exposure, it was developed with ferrous sulfate solution and fixed with potassium cyanide solution. The density of the image obtained after wet film fixation is not high enough (black), and it is necessary to repeatedly “thicken” the solution with copper sulfate, potassium iodide, silver nitrate, etc. to increase the image density. Finally, the sodium sulfide solution was blackened to obtain a black and white negative negative film. Pour a layer of gum arabic solution on the photosensitive film to protect the layout. At this point, wet version photography was completed.

The above process is completely manual operation. There are many chemical reactions in the process, changes in the temperature and humidity of the environment, the quality and performance of chemicals, process recipes, and the proficiency of the operators can affect the photographic results. Therefore, wet film photography is an old and obsolete technology that hinders personal health. However, due to the fact that the cost of wet films is cheaper than that of imported films, the contrast between black and white is high. For economic reasons, printing plants have been using them.

However, in the case of continuous black and white or color originals, films have to be used. In the 1950s, China could not produce films, and it had to be imported from abroad each year. Among them were Agfa of Germany, Elf of the United Kingdom, and Kodak of the United States, to meet the needs of the domestic printing industry.

In the early 1960s, the Shantou Photographic Chemical Factory cooperated with the Beijing Institute of Printing Technology to produce the "AD" brand plate-making film, which filled the blank of the Chinese-made film and ended the history of China's printing industry completely relying on the "foreign" film. Since the 1970s, a large number of "Huaguang" plate-making films produced by the Second Film Factory of the Ministry of Chemical Industry have been on the market, and domestically produced plate-making films basically meet the needs of printing and photolithography. With the availability of domestic film security, coupled with the promotion of direct web-based photographic color separation in the late 1970s, the use of wet films has declined. Since the 1980s, in the large-scale printing factories, domestic film completely replaced the Luodian Wet Plate, which has been used for more than 100 years, and has completed the transformation of "wet and dry" and "soft and hard" in the history of Chinese photographic platemaking.

Second, the development of color separation technology

Photography is the copy of the original. The manuscripts are varied. There are black-and-white manuscripts, colored manuscripts; text, lines, field, color block manuscripts, and more are continuous tone manuscripts with a high-gloss level. Faced with continuous color originals, photography is the first step in color separation. That is, the color image of the original document is decomposed into printing four basic colors: four monochrome images of yellow, magenta, cyan, and black, which is photo separation. Although the photoengraving plate has flat, convex, concave, and hole points, the color separation in the previous stage is basically similar regardless of the type of the posterior system.

1. Early artificial separation of colors

Prior to the 1960s, photographic platemaking technology was not very popular. At that time, color photography was rare. When you encounter a black-and-white photo manuscript and want to print it into a color picture, you have to artificially separate the colors. Separators use sophisticated craftsmanship to modify their originals into printed yellow, magenta, cyan, and trichromatic colors based on their rich experience in life and color imagination. And make the component color version, after printing overprint, the prints will present the natural appearance of the scenery color. In the fifties, the People's Pictorial and the Popular Movie were a lot of color pictures. The original manuscript was originally a black-and-white photograph. It was printed in a color picture using this color separation method. However, this process technology has a long platemaking cycle and is difficult to operate. It not only requires that the color separation personnel have superb editing skills, but also has certain painting and color art culture.

Since the 1960s, with the popularity of color photography, the proportion of color manuscripts has become larger and larger, and black and white photographs have artificially imagined that the color separation gradually decreases, and the color separation of color manuscripts becomes the mainstream of color separation technology.

2. Photo separation

Before the 1950s, there were very few people who truly mastered camera separation in China.

Photo separation is the use of color science to color light the principle of three primary colors, the principle of complementary colors to use different color filter cleverly, when the camera separation, only one color light on the screen through, the rest of the color light is absorbed by the filter (filter To), a photographic method of printing a basic color image is formed on the photosensitive material. After obtaining the color separation, the color separation film is obtained. The relationship between color manuscripts, filters, and color separations is as follows:

Red filter → Green Separator Overcast Color Originals Green Filters Magenta Separation Sequins Blue Filters Yellow Separation Sequins

According to the principle of complementary colors, red and blue are complementary colors, and the red filter absorbs all the cyan of the original and forms a transparent Qingyin tablet on the separated color film. Green and magenta are a pair of complementary colors, and the green filter absorbs all the magenta of the original and forms a transparent magenta shade on the color separation film. Blue and yellow are a pair of complementary colors. The blue filter absorbs all the original yellow and forms a transparent yellowish film on the separated film. The level of transparency on the negative film corresponds to the size of the Internet.

Sometimes, in order to make up for the defects of the three-color inks and better reproduce the changes in the shades of the printed matter, a black shading film is also added.

3. Manual revision

In color separation technology, color decomposition and color correction complement each other. The color correction in the 1950s mainly relied on artificial rectification, commonly known as revision (color picture 23-4). Of course, artificial retouching is easier than artificially considering color separation, but it is not an overnight effort to get acquainted. At that time, the quality of color print reproduction was not largely determined by the separation of photographs, but by manual revision. In the 1950s, Shanghai Xu Shengji Printing Factory, Shanghai Zhonghua Book Printing Factory, and Beijing Xinhua Printing Factory all had several skilled revision personnel who used their two-handed correction color printing to print out “China” and “Indonesia President of the Republic of Sukarno-Ph.D. Collection of Tibetan Paintings, "Yongle Palace Mural" and "Shanghai Museum of Tibetan Painting" and other fine exquisite album. The last three albums were exhibited at the Leipzig International Book Art Exhibition of the German Democratic Republic in 1959 and won the gold award for book binding.

Coloring book 23-4

4. Apply mask technology

In the late 1950s, the use of mask technology began to be applied in camera color separation. This was achieved by photographing a mask with a certain density beforehand. When photographing or copying again, the color or tone correction was performed under the cooperation of the mask and mask. One way. The mask correction method eliminated a lot of manual corrections, shortened the plate making cycle, improved the printing quality, and raised the color printing level by one step.

Manual revisions, mask corrections, etc., cannot always achieve satisfactory copying results. Prior to the 1970s, in order to compensate for the lack of color separation, lithographic photography often added a light magenta and light blue (commonly known as Xiaohong and Xiaolan) on the basis of the yellow, magenta, and blue three-color editions, plus the black edition. , Color flat printing for six-color printing, sometimes with spot colors, a screen to print 7-8 color version. In this way, although the copying effect is better, the cycle of plate making and printing can be longer and the cost is higher.

5. Direct color separation

For a long time, the transfer of photo separation and revision techniques relied on masters and teachers, hand-to-hand and word-to-hand, and the teachers were honoured with their lives. The emphasis was on the accumulation of experience and the lack of emphasis on scientific and standardized operations. Therefore, technological progress has not been great for several decades. It was not until the late 1970s that there was a breakthrough.

In June 1977, Beijing, Shanghai, Liaoning, and Shaanxi provinces and municipalities held an experience exchange meeting for new process of photolithography and printing in Xi'an. The central theme of the conference was the advanced experience of the exchange of lithography and direct-web separation and four-color printing.

The feature of the new process is that during the photographing, the color separation passes through the net and is completed at the same time, and the color separation passes through the net negative film. There are no "tails" for color separation, no red and blue versions, and only yellow, magenta, cyan and black versions. The key to the new experience is that every variable factor in the process such as the color of the original, the contrast of the tone, the density contrast of the mask, the exposure time, the developer formulation and the developer temperature, and the development time must be