Bipack procedure

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The bipack method was used in early cinema technology, i.a. a. to make trick shots . Early color film techniques were also based on bi-pack processes.

Trick technique

For scenes in which two pieces of film to be recorded separately are to be combined, two film strips are placed directly on top of one another in a special camera or in special reels. One of the two film strips is unexposed, the other is already exposed and developed. If the already exposed strip contains z. For example, a thunderstorm recording with rapidly moving clouds, the scene that is recorded using the bipack method (e.g. a dialogue between actors in the studio) can be seen in the finished film against the background of the thunderstorm.

The image areas of the strips must be covered in a complementary manner. This is achieved when recording with masking masks in front of the camera. In the example, when recording the thunderstorm, a mask would have been used for the lower area and for the studio dialog a mask in the upper area of ​​the respective film strip (in the finished image the thunderstorm can be seen above, the dialogue below).

In contrast to an optical printer , no lenses or other optical aids are used in the bipack process ; the film strips lie flat on top of one another (contact copy).

Color film

The bipack process ( two-strip ) was used as a recording technique for cinema two-color film before the development of a sufficiently mature monopack process. Here, two differently sensitized film strips of black and white film , one of which is sensitive to blue-green, but not to red, while the other strip is only sensitive to red-orange ( orthochromatic ), are exposed together. After development , the different color separations become visible on the resulting film strip. The desired color impression is only created through the joint projection of the two superimposed films.

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