When people watch a modern traditional photographic image and a digital image, only a little attention to observation and analysis will be able to tell that the image is lifelike, full and soft, and the beauty of color is the traditional photographic material image. The other looks bright and colorful, anti-differential, clear-cut digital image printing. Why are their respective advantages so distinct? This is explained from their respective imaging principles and production processes.
1 Imaging principle and production process of modern traditional photographic photographic imaging materials
Modern conventional photographic materials include general art photographic filmstrips, photographic papers, telecine films, aerographic films, medical radiographs, films used in printing plates, films for certain microfilms, astrophotography plates, and the like.
Generally, the conventional modern photographic light-sensitive material cannot obtain images directly after the photographic exposure. Usually, visible and long-lasting images can be obtained after chemical treatment such as development, fixation, water washing, and drying. Such a complicated imaging process is divided into three basic stages. , The photographic exposure stage (formation of latent images), and the development stage (formation of visible images).
1.1 Photosensitive material preparation stage
The first is the preparation of photographic emulsions. Different types of photographic film are required for different purposes. The raw materials used in the preparation of photographic emulsions are different from the recipes and methods used in the production process. According to the formulation and technology of various kinds of tablets, potassium bromide (potassium halide, potassium iodide) and silver nitrate solution prepared in the bright room are injected into a photographic gelatin aqueous solution at a certain temperature that is being stirred in a dark room by a double injection method. The potassium bromide reacts with silver nitrate to form a precipitate of silver bromide and is uniformly deposited on a gelatin carrier as a photographic emulsion.
Under a dark light, the emulsion is subjected to a very complicated manufacturing process, such as removing potassium nitrate with ice water, adding sensitizers, antifoggants, leveling agents, defoamers, hardeners and other chemical reagents. Become an official photographic emulsion that can be coated.
Coating and finishing section: The above photosensitive photographic emulsion is tempered to a temperature of 5 to 8°C in a dark room, injected into a coater coating tank, and then coated onto a film base or a photographic photographic paper carrier and dried at a low temperature to dry it. Cut, punch, after passing the test, packaged into products, put into storage, put on the market.
1.2 Traditional Film Exposure Stage
When the photosensitive center on the silver bromide crystal in the photosensitive material film is exposed, a chemical change occurs due to absorption of light energy, so that a portion of the silver bromide decomposes to produce a silver latent image and bromine. During exposure, the density of the latent image formed by the film irradiated by the strong light is large, and on the contrary, the latent image center piece. They will affect the next development speed and the impact of the density of metal silver particles and image quality (Figure 1).
After the exposure, the latent image and the sub-latent image are enhanced and the latent image is changed.
Fig.1 Schematic diagram of the change of photosensitivity center during exposure of silver halide
1.3 Traditional Photographic Materials Development Stage
Developing is the use of a developer to reduce the silver bromide crystal grains in the exposed silver halide emulsion to chemically change to produce metallic silver particles. Therefore, to study the progress of development, it is also possible to start by studying the development of individual silver halide crystals. The development of silver halide grains always starts from a certain point or points above. The reason why the development effect starts from a certain point or points above is due to the effect of the latent image. The latent image can prompt the silver halide around it to be quickly reduced to metallic silver. When these silver halides are reduced, they can promote the reduction of the surrounding silver halide until the entire silver halide is reduced. The latent image plays a catalytic role in developing or accelerating the reduction of silver halide in the development process (see Figure 2).
Figure 2 Schematic diagram of the process from exposure to development
The structure of the metallic silver particles obtained by the development is not a solid mass but a filamentous structure having a size roughly equivalent to that of the original particles.
From the above, it can be seen that particles of silver ions, metallic silver particles play an absolutely decisive role both in the preparation of emulsions and in the exposure and development of films or photographic papers. Because their fine particles are close to the size of the nanometer scale, the images that are dispersed and gathered together by the delicate particles are beautiful in color, soft and delicate in contrast, and are full of distinct layers, making people enjoy the most beautiful art enjoyment when viewing.
The use of modern traditional photographic photographic materials is extremely versatile. Such as fine art photography, tourism scenes, wedding photography, celebrity great man standard portraits, paintings of famous painters, as well as cultural and educational sports and health, industrial and agricultural production, scientific research, printing and electronic circuit middle plate and other activities in the video.