Basic introduction Chinese name: film mbth: Film? Nickname: film use: basic information of photos, classification, film size, photosensitive type, packaging method, size, development, basic information In PCB terminology, negative often refers to black and white negative. As for the brown "azo film", it was named by another photographic tool. The negatives used in printed circuit boards can be divided into "original negatives" and "working negatives". Film sensitivity (ISO) refers to the data of the International Lighting Organization, and film ASA refers to the abbreviation of American Standards Institute. ISO and ASA refer to the same data. Films are classified according to photosensitive speed, from the lowest ISO 25 degrees to the highest ISO 3600. According to the film size, there are 120 (large negative), 135 (most commonly used), 1 10, etc. , and 8"X 10 "large negatives for shooting advertisements or large posters. Film is divided into black and white film, color film, infrared film and so on. Classified film sizes are commonly used 120 (medium film), 135 (most commonly used, film width is 35mm), 1 10 (small box type) and so on. , and 4"x5 "or 8"x 10 for shooting advertisements or large posters. Before the 1960s, the commonly used film specification was 120. Since then, due to the development of lens production technology, the lens quality of low-priced 135 cameras has been greatly improved, and 135 film has become popular. It was not until the color photography technology matured in the 1970s that fully automatic 135 color developing and drying cameras flooded the market, and 120 negative was officially replaced. There are black and white negatives, color negative, infrared negatives and X-ray negatives. Color negative is divided into sunshine sheet and light sheet according to the color temperature of different light sources. If you shoot the scenery in the sun with a daylighting film, the color of the photo will be blue, otherwise it will be yellow. Packaging methods can be divided into soft film and hard film. Films made into strips and rolls are also called films. 120 filmable 12 6x6, commonly known as 2.5-inch negative. Roll it up with a long opaque paper roll and insert one end on a shaft made of iron. The paper is black inside and yellow outside (also pink green), and the words 1 to 12 are printed. There is a small window hole behind the camera. Turn the scroll handle or button to see if the numbers are aligned with the window. 135 film can take 36 negatives, commonly known as 1 inch. There is a hole in the film base (see figure) and a gear hook hole in the camera. When shooting, turn the handle to pass the film. Size millimeter (8 mm): 8 mm is the narrowest film with the smallest size. 1932, used for amateur and family films. Because of the low cost of negatives and films, many avant-garde and underground films also like to use 8 mm wide film negatives. Since the middle of 1960' s, 8 mm wide film negatives have been gradually replaced by super 8 mm film negatives. @ Over 8mm: 1965. 8 mm wide, but the quality is better than the standard 8 mm size, and the picture is bigger. Now it has largely replaced the 8 mm film. It is most commonly used in the fields of education, marketing, industrial training and home movies, and also used for reducing and developing the original camera film and 16 cm film. @ 16mm (16mm): negative with a width of 16mm. In silent movies, there are rows of holes on both sides of 16 mm film; On the other hand, movies with sound only have holes on one side, and the other side is used as an audio track. This kind of film was introduced into the amateur market on 1923, and gradually developed into a common media for family filmmakers who are not shown in general cinemas. Movies of this size are mostly used in independent short films, documentaries and educational films. [2] Super 16mm (Super 16mm):1971year. The picture of Super 16mm film is 40-46% larger than that of standard16mm film. Because of the low cost, films above 16 mm are often enlarged to 35 cm when shown in cinemas. @ 35mm (35mm): the width is 35mm, each frame has four rows of holes on each side, and one foot consists of 16 frames. Since the earliest film development, this kind of film has been the standard size film for professional film production. @ 65mm (65mm): 65mm wide, with sprocket positioning holes on both sides. Usually converted into 70 mm slides for film screening. @ 70mm (70mm): 70mm wide, with sprocket positioning holes on both sides. Movies shot with 35 mm or 65 mm negatives can be converted and enlarged into 70 mm wide negatives for broadcasting and distribution on the wide screen of cinemas. The development of American film industry and the rapid development of photosensitive material production technology. American photography technology has always been in the leading position in the world. The famous negative brands are Kodak, Agfa and Fuji. China's domestic photosensitive material industry began in the 1940s. Returned overseas Chinese from Nanyang founded Gong Yuan Photosensitive Material Factory in Shantou, Guangdong Province, producing Gong Yuan brand black-and-white film and photographic paper. Since then, Shanghai and Baoding have also produced black and white photographic materials. The research and development of color photography technology in China started too late, and Baoding began the trial production of color film in the 1970s. Due to poor quality and lack of matching cameras and processors, living space is lost. In the mid-1980s, foreign color photographic materials flooded into China and dominated the China market for more than 20 years. China's photosensitive material industry has completely declined. In the 20th century, the rapid development of computer technology and the invention of D promoted the popularization of digital imaging technology and the complete decline of photosensitive chemical industry. There are not many people taking photos with negative films today, although negative films have irreplaceable advantages. For example, the film area of 135 is larger than that of most digital cameras (digital media). If you want to take large photos, it is better to use film. In addition, the film image has strong layering, natural color (simulated color), fine picture quality (high pixel) and large tolerance (easy to keep bright or dark details), and the imaging quality is better than that of digital cameras. Especially in the case of dark light, it is necessary to shoot with long exposure, or to develop rationally when developing the negative film (increase the developer concentration or lengthen the development time). For example, Kodak Tri-X 400 is rationally developed to iso 1600, and even Kodak T-max p3200 is rationally developed to iso 6400, but long exposure will produce a lot of noise in digital photography, so some photographers have good imaging quality. Although you can take high-quality photos with negative film, you need to be familiar with darkroom skills. Generally speaking, it is difficult for fast film shops to give full play to the advantages of negative films. Therefore, it is best for photographers who use negative films to print photos themselves. For example, they can expose photos in different areas and adjust the contrast and cropping of photos themselves. In addition, because the toxicity of chemicals used in black-and-white printing is much lower than that in color printing, and the printing process is simpler, many people do manual printing in black-and-white darkroom, and color negative films are mostly avoided by automatic printing machine. Digital photography has incomparable advantages in imaging, storage, transmission, collection and retrieval. The receiver can see the scene in the lens thousands of miles away through the network. Photos stored in the matchbox memory can be piled up in a room with enough film. With the development of digital technology, the film market is shrinking year by year. However, due to the existence of digital film, the advantages of film photography in the field of large-format photography, and the unique "hair color" of film (referring to the more realistic color of film), film photography may coexist with digital photography for a long time.