What is a negative?

Photographic film

The negative is also the photographic film. Film is silver salt photosensitive film, also called film. Made of PC/PP/PET/PVC material. Photographic film is made by applying silver halide on an acetic acid base. When light shines on the silver halide, the silver halide turns into black silver and is fixed to the base after the development process, becoming the common black and white negative film we see. Color negative film is coated with three layers of silver halide to represent the three primary colors. In addition to negative films, there are also positive films, primary imaging films, etc. The photographic film is what people often call inverting black and white, because the camera itself uses objects placed outside the focal length of the convex lens twice as long. Therefore, the people and images in the photographic film are actually reversed.

The film is coated with photosensitive agent. When people take pictures, because the light-colored parts have a relatively strong ability to reflect light, the reflected light enters the camera's dark box and the photosensitive agent in the film appears. Chemical effect, and the dark-colored part has a higher ability to absorb light, so only less reflected light enters the film.

As a result, the light-colored parts in the film are very sensitive to light, while the dark-colored parts are just opposite to the light-colored parts and are relatively weak. During the process of developing the film, the photosensitive agent in the weakly sensitive part is easily washed away, so it basically appears as a light color. However, the photochemical reaction occurred in the parts that are more sensitive to light and cannot be washed cleanly. Therefore, the color that appears is a dark color.

In PCB terminology, film mostly refers to black and white film. As for the brown "Diazo Film" (Diazo Film), it is named after Phototool. The negatives used in PCB can be divided into the "original negatives" MasterArtwork and the reproduced "working negatives" WorkingArtwork, etc.

Film sensitivity (ISO) refers to the data of the International Illuminating Organization. Film ASA refers to the abbreviation of the American Standards Association. ISO and ASA refer to the same data. Films are classified according to their photosensitive speed, ranging from the lowest speed of ISO25 to the high speed of ISO3600.

The film types are divided into commonly used types such as 120 (large negative), 135 (the most commonly used), 110, etc., as well as other types such as 8" designed for shooting advertisements or large posters. X10" large format negative. Films are classified by photosensitive type, including black and white film, color film, infrared film, etc.

Purpose of negative film

Negative film is the light-sensitive material used in photography. Films include positive films and negative films, the positive films are for projection. It requires fine grain, high contrast, low fog, high resolution and sharpness, and negative film is used for shooting pictures. High sensitivity and wide latitude are required. Film includes positive and negative films.

Color film can be divided into two major types, namely reversal film and negative film. Color reversal film, sometimes also called slide film, is a film that directly obtains a color transparent positive image after reversal processing. Color reversal films can be viewed directly on a screen using a slide projector, or viewed on a film viewing light box. Photos can be printed directly or used as original films for color separation plate printing.