What are the differences between professional film, negative film and ordinary film, and what are their parameters?

Types of film: Film used for photography includes black and white film and color film, which are divided into 120 film and 135 film according to different sizes.

120 film can take pictures of different sizes according to different 120 cameras, including those that take 16 negatives (the frame is 4.5 × 6 cm); those that take 12 negatives (6 × 6 cm) ); there are also those that take 10 negatives (6×7 cm) and 8 negatives (6×9 cm). The length of 120 film is generally 81-82.5 cm, and the width is 6.1-6.5 cm. The number of negatives taken with 120 film varies depending on the model of camera.

135 film is suitable for various models of 135 cameras. A roll of 135 film can take 36 pictures of 24×36 mm. The length of 135 film is generally 160-170 cm and the width is 3.5 cm. This film has regularly arranged holes on both sides.

Black and white film: According to color sensitivity, it is also classified into panchromatic film, color separation film, color blind film, infrared film, X-ray film, etc. What we commonly use is full-color film, which can display various colors in nature, such as red, orange, yellow, green, cyan, blue, and purple, in different shades of black tones. This means it is sensitive to all visible light. In addition to detecting blue and purple in visible light, the color separation film can also detect yellow and green, but it cannot detect red. This film is often used in printing and platemaking, and sometimes in landscape photography. Color-blind films are more sensitive to blue-violet light in visible light and very insensitive to green and red light. This film is suitable for black patterns, graphics and text reproduction. Infrared films, which specifically sense light with wavelengths longer than red light, are generally used in aviation and military photography.

Sensitivity of the film: Sensitivity is the sensitivity of the film to light, and it is also the photosensitive ability and symbol of the film. Films that can be sensitive to light when the light is very weak are called high-speed (fast) films; on the contrary, films with low sensitivity must be shot in situations with strong light. If you use different sensitivities under the same light conditions, When shooting with high-sensitivity film, the aperture or shutter speed of the camera should change. In other words, for high-sensitivity film, the aperture should be smaller and the shutter speed should be faster; for low-sensitivity film, on the contrary, the aperture should be larger. Or the shutter speed needs to be slower.

According to the level of sensitivity, it can be divided into fast film (GB24° and above), medium speed film (GB21°), and slow film (GB18°) and below.

Sensitivity has many names, the common ones are the American ASA system and the German DIN system ("customized" system). Our country adopts the GB (national standard) system, which is equivalent to the DIN system.

my country's GB national standard system, for every GB3° increase, the sensitivity doubles. For example, GB24° film is twice as sensitive as GB21° film. Various sensitivity standards can be converted to each other. ASA100 is equivalent to GB21° or 21DIN.

Selection of black and white film: How to choose low-speed, medium-speed or high-speed film depends on different requirements such as the subject, shooting conditions, and final photo magnification.

Generally, when shooting outdoors, where the lighting conditions are good, the scenery is bright, and the contrast is large, it is better to use 21DIN medium-speed film. If the contrast of the scenery is dull, you can choose a low-speed film with a slightly higher contrast.

When shooting indoors, if the subject is moving, whether using natural light or lighting, you should choose a film with high sensitivity to avoid underexposure affecting the image quality, or the exposure time being too long. Long and moving objects create blurry images. When shooting with flash, 21DIN or higher-sensitivity film is generally used, so that not only the sensitivity index can be larger, but also the latitude is larger due to the higher sensitivity, so that the contrast of the film will not be too large.

For sports shooting, it is generally not advisable to use flash. Sports shooting has a strong sense of movement, so use high-speed film (such as 24DIN, 27DIN).

For stage photography, it is generally not advisable to use flash. It must use higher-sensitivity film.

Taking portraits, still life, and landscape photos requires rich layers, fine silver grains, strong texture, and pleasing and harmonious tones. Low-speed and medium-speed films should be used as much as possible.

Color film: Color films used in photography include color negative film and color reversal film.

Color negative film, after it is developed, the color on the negative film (film) is the complementary color negative image of the original object color. Color negative film is mainly used to produce color photos; it can also directly print and display black and white photos, but the level and contrast of the photos will be affected to a certain extent. The photosensitivity latitude of color negative film is much smaller than that of black and white film. The film is affected by the color temperature and surrounding environment during shooting, causing a color cast. However, it can be corrected by using different color filters during photo production. Color negative film is the most widely used type of color film.

Color reversal film, after undergoing a reversal processing process, can obtain the same color positive image as the subject. The color image, color reproduction and image clarity of color reversal film are better than color photos, and plate making and printing with color reversal film is better than color photos. Color reversal film, its colors are true, bright and full.

The requirements for shooting are strict, the photosensitivity latitude is very small, and the exposure is required to be accurate. If the exposure differs by 1/2 times, various colors, densities, and layers will be significantly affected.