What is the difference between professional film, negative film and ordinary film, and what are the parameters

Types of film: photographic film has black and white film and color film, according to different sizes are divided into 120 film, 135 film two.

120 film according to different 120 cameras can be shot in different sizes of the picture, including shooting 16 negatives (4.5 × 6 cm); shooting 12 negatives (6 × 6 cm); and shooting 10 negatives (6 × 7 cm) and 8 negatives (6 × 9 cm). 120 film is generally 81-82.5 cm in length, width of 6.1-6.5 cm, and the length of the film is 81-82.5 cm. The number of negatives taken on 120 film varies depending on the camera model.

135 film adapted to various models of 135 cameras. A roll of 135 film can shoot 36 images of 24 × 36 mm film. 135 film length is generally 160-170 cm, width of 3.5 cm. This type of film has regularly arranged holes on both sides of the film.

Black and white film: according to the color-sensitive properties are also classified as panchromatic film, color separation film, color blind film, infrared film, X-ray film and so on. We commonly use panchromatic film, it is a variety of colors of nature, red, orange, yellow, green, cyan, blue, purple can be displayed in different shades of black tones. That is to say it is photosensitive to all visible light. Dichroic film in addition to feeling the visible light in the blue, purple, but also feel the yellow, green, for red it can not feel. This type of film is often used for printing plates and sometimes for landscape photography. Color-blind film, which is more sensitive to blue and violet light in visible light, and very insensitive to green and red light. This type of film is suitable for black patterns, charts and text reproductions. Infrared film, specializing in feeling the wavelength of light than red light, generally used for aviation, military photography.

Film sensitivity: sensitivity is the film's sensitivity to light, but also the film has the ability to sense light and signs. Film in the light is very weak in the case of light-sensitive, high-speed sensitivity (fast) film; on the contrary, low sensitivity film, it must be in the light of the occasion to shoot, if in the same light conditions, the use of different sensitivity of the film shooting, the aperture of the camera or the shutter speed should change, that is to say, high light sensitivity film, aperture should be smaller shutter speed faster; low sensitivity film is the opposite, aperture should be faster; low sensitivity film is the opposite, the aperture should be the same, the aperture should be the same. film is the opposite, the aperture should be larger or slower shutter speed.

Based on the sensitivity of the film can be divided into fast film (GB24 ° and above), medium-speed film (GB21 °), slow film (GB18 °) below.

The sensitivity has a variety of names, common in the United States ASA system and the German DIN system ("fixed" system). China adopts the GB (i.e., national standard) system, comparable to the DIN system.

China's GB national standard system, every GB3 °, its sensitivity doubled. Such as GB24 ° film is twice as fast as GB21 ° film sensitivity. Various sensitivity standards, can be converted to each other. ASA100 is equivalent to GB21 ° or 21DIN.

Black and white film selection: how to choose low-speed, medium-speed or high-speed film, according to the object of the shooting, shooting conditions, as well as the final photo magnification and other different requirements to decide.

Generally speaking, in outdoor shooting, light conditions are better, the scenery is bright, the contrast is also large when the choice of 21DIN medium-speed film is appropriate. If the contrast of the scene is flat, you can use low-speed film with slightly higher contrast.

In indoor shooting, if the subject has a sense of movement, whether with natural light or light, you should choose a high sensitivity film, you can avoid underexposure to affect the image level, or because the exposure time is too long to make the formation of objects with a sense of movement image blurred. The use of flash photography, the general selection of 21DIN or more sensitive film, so that not only the sensitivity index can be larger, and because of its high sensitivity tolerance is also large, do not lead to the negative contrast is too large.

Sports shooting, generally should not use the flash, sports shooting strong sense of movement, to use high-speed sensitivity (such as 24DIN, 27DIN) of the film.

Stage photography, generally should not use the flash, it must choose a higher sensitivity of the film.

Photographing portraits, still lifes, landscape photographs, the requirements of a rich hierarchy, silver grain fine, strong texture, pleasing and harmonious tone, should try to use low-speed and medium-speed film.

Color film: color film for photography has color negative film and color reversal film.

Color negative film, it is developed, the negative (negative) on the color is the original object color complementary negative image. Color negative film is mainly used for the production of color photographs; and can be directly printed, put black and white photos, but the level of the photo, the contrast is affected to some extent. Color negative film shooting sensitivity tolerance than black and white film is much smaller. In the shooting by the color temperature and the influence of the surrounding environment, resulting in the negative off-color, but can be used in the production of photographs with different color filters in order to correct. Color negative film is the most widely used type of color film.

Color reversal film, it is after the reversal of the processing process, you can get and the subject of the same color positive image. Color reversal film color image, color reproduction and image clarity are better than color photographs, with color reversal film plate printing is better than color photographs. Color reversal film, its color is true, bright, full. Shooting requirements are strict, light sensitivity tolerance is very small, requiring accurate exposure, if the exposure difference 1/2 times, a variety of colors and density, levels will be significantly affected.