Questions about movies

When the earliest movies with sound were released, the phonograph, artificial sound and so on. Used to match sounds and pictures, or to express dialogue with subtitles. Optical recording appeared from the early 1930s to the early 1950s.

There are two types of optical recording methods:

Densification: Change the density of the exposed part of the film.

Variable product formula: change the width (area) of the exposed part of the film.

In both types, the light modulated by the light modulator passes through a narrow gap, so that the film moving at a constant speed can be exposed in a certain range. This gap must be very narrow for recording high frequency.

Optical recording principle

Variable product optical recording

The whole recording process includes recording and playback.

(1) The microphone converts the sound in the air into corresponding analog electrical signals, or converts the mechanical energy of the diaphragm on the microphone into electrical energy.

(2) The recording amplifier will improve the analog electrical signal output by the microphone to a suitable level without distortion.

③ The optical modulator converts the electric signal output by the amplifier into an optical signal to control the exposure on the vocal film. When a sound film passes through the light blade of the light modulator, exposures corresponding to electrical signals are obtained at different positions, so that sound signals are recorded on the film.

(4) The recording and film conveying mechanism makes the film pass through the exposure point at a uniform speed. When taking pictures, the film is required to pass through the exposure window intermittently. Because recording and photography have different requirements for film transmission, and because shooting and recording are both required at the same time, we should adopt the dual-film system, so that both photography and recording can be carried out on our own equipment.

⑤ The playback film conveying mechanism makes the copied vocal cords pass through the playback scanning part of the projection system evenly at the recording speed. Projectors are used to show copies of pictures and sounds. Because the picture needs to pass through the window intermittently and the vocal cords need to pass through the sound scanning part at a constant speed, the two parts must be separated. The copy mounted on the projector is transported from top to bottom, and the sound reproduction scanning part is located at the lower part of the picture window, so the vocal cords and picture positions on the film copy should also be staggered back and forth. According to international regulations, the sound track of 35 mm film is 20 frames ahead of the corresponding picture, and the sound track of 16 mm film is 26 frames ahead of the corresponding picture, which ensures the synchronization of sound and picture.

⑥ The optical playback scanning part consists of a stable light source, optical elements and photovoltaic cells, and converts the optical signals with different widths or densities on the vocal cords into electrical signals. The stable light source forms a light blade at right angles to the thin film on the optical element through the gap, and irradiates the photoelectric cell through the vocal cord. Because the exposure density or exposure width of the upper vocal tract is different, the light transmitted to the photoelectric cell changes accordingly, so the audio analog signal recorded on the copy is also returned as an electrical signal.

⑦ The sound amplifier improves the electric energy output by the photocell to a suitable level. ⑧ The loudspeaker converts the electric signal output by the reduction amplifier into sound, or reproduces the sound originally acting on the microphone diaphragm.

Early optical recording vehicle system equipment. Mechanical Phillips-Miller system. Longitudinal needle engraving technology is directly applied to film materials, and sound is directly recorded on the film. The biggest defect of early traditional optical recording is that the photosensitive film used is a disposable recording material, which cannot be modified and reused once exposed. In 1950s, magnetic recording began to be used for film recording. The magnetic tape used for magnetic recording can be reused many times, which greatly reduces the production cost. But a large number of copies are still based on optical recording. In the1980s, magnetic recording and optical recording were used together.

Nowadays, movies are generally digital photography, and the film cost is too high. Nolan is the only director who still uses film, whether it is Inception, Interstellar or Dunkirk. So far, I can't understand it. As for the special effects and editing, the film is converted into digital format in the computer, using colloidal technology. This technology is very old. I don't know what it looks like now. The person who posted it is very good at it. I don't understand. Web links.