Recording development

The process of recording all kinds of sounds matched with the picture at all stages of making sound films. No matter which manufacturing stage the recorded sound is, when it is finally made into a reproduction vocal cord, it should not only be synchronized with the picture, but also pay attention to the continuity and integrity of the whole film. Audio film appeared in the middle and late 1920s. In the process of development, it has successively selected several methods: mechanical recording (record recording), optical recording (photosensitive recording) and magnetic recording.

Mechanical recording

In the mid-1920s, records made by mechanical recording method were used to record and restore sound for audio films. For example, the audio feature films don Juan (1926) and jazz singer (1927) made in the United States are recorded mechanically. China's early audio feature films "singing girl red peony" and "beauty Yu" were also recorded in this way. Although mechanical recording played a certain role in the early stage of the development of audio films, due to the separation of records and films, it often presents the phenomenon of asynchronous sound and painting in cinemas. Sometimes the picture has already been played, and the sound on the record continues.

Optical recording

As early as the early stage of film development, many people put forward the imagination of using film to record and return sound. It was not until the early 1930s that the optical recording method was successfully applied to the film. The feature film produced by optical recording method as early as 1937 is the seven heavy days in the United States. Audio feature films made by optical recording method in China include "the sky is green after the rain" and "spring in the song field". By the 1980s, the vocal cords in general film reproduction were still recorded optically. In film reproduction, one side of the picture can be seen with traces of recorded sound, which is called optical sound trace or vocal cord.

Optical recording的进程，是把传声器所拾取的声响转换为相应的模仿电信号，再通过音频扩大器把它扩大到足以使光－电调幅器起作用的程度，以构成可记载的模仿光信号。光－电调幅器是光学录音的要害部件，它把声响的模仿电信号转换成声响的模仿光信号，并运用胶片对不同曝光量发生不同感光密度的特性，把声响记载下来。对通过录音的胶片进行显影、定影、冲刷加工之后，就能显示出感光密度不同或感光宽度不同的光学声带。和机械录音比较，光学录音的优越性在于它所录制的音域规模较大；它和电影摄影所用的前言都是感光资料，能够和画面一起印在复制上，这种办法既降低了制造成本、保证了声响质量，又使放映时的声画同步。

Optical recording改进了有声电影。前期的有声电影几乎全部是选用光学录音的。50年代中期以前，我国的电影出产基本上也选用这种办法。但是，光学录音也有不足之处：①录音后的感光胶片要进行冲刷，才干得到声带底片，制造进程比较复杂。②复制上的声带也象画面一样需要从录音底片上印制出声带正片才干还音，所以光学录音不能当即还音，不能及时查看录音作用。③感光胶片的声带上如有脏点或机械划伤，就会发生噪声，影响声响质量。④感光胶片有必要在黑私自操作，工作不便利。⑤由于第②条缺陷和剪接的需要，用的胶片很多，了制造成本。

Magnetic recording

From the late 1940s to the early 1950s, Americans introduced the tape recording technology successfully developed by Germans, Danes and Swedes before World War II into film recording, which greatly changed the film recording technology relying solely on optical recording in the past. From original audio tape data to mixed recording, it has gradually changed to magnetic recording, Optical recording is only used to make duplicate optical tapes. The key component of magnetic recording is the magnetic head, which converts the analog electrical signal of sound into analog magnetic signal and records it on the magnetic medium. There are two types of magnetic media for film recording: one is magnetic film, which has the same size as film film, and also uses film hole for film transmission. The difference is that the photosensitive coating is changed into a magnetizable magnetic coating. The commonly used magnetic film widths are 35 mm, 17.5 mm and 16 mm. The second is magnetic tape. It has no holes and is transmitted by conflict. The commonly used tape is 6.25 mm wide. Music recording also uses 25.4 mm and 51.8 mm wide tapes; Sometimes 3.81mm wide cassette tapes are used for location ambient sound recording.

Magnetic recording比光学录音便利得多，能够当即还音，查看作用，若不满足，能够重录，然后省去了一系列感光冲刷加工工序，大大节省了时刻和资料。磁片或磁带无需加工，不会呈现加工进程中可能的声响失真，并且磁性录音噪声小、频带宽、动态规模大、质量高。

When magnetic recording is used in film production, it is necessary to turn magnetic vocal cords into optical vocal cord negatives for many manufacturing, distribution and reproduction. Someone once imagined that the last optical recording would also be replaced by magnetic recording, that is, a long and narrow magnetic strip would be painted on the sound track orientation of the film reproduction, and the sound would be recorded on it. However, this will make the production of film reproduction more cumbersome. The film should be coated with both photosensitive emulsion and magnetic data layer, and each reproduction should be recorded separately, viewed separately, and all projectors should be modified. Therefore, this method is not necessary for other film reproduction except for 70mm stereo films and a small number of films for special purposes.

Film recording process

A film records the sound of the scene together with some pictures, which is called simultaneous recording; Some are not suitable for on-site recording. For example, it is inconvenient to record in the noisy environment of natural location or match the sound after the picture is made because the actors have difficulty in pronunciation, which is called post recording; Some need to record the sound in advance, and then release the sound when taking pictures, so that the actors can listen to the rhythm of the sound, such as arranging Chinese Peking Opera and opera films, which is called early recording. Usually, the sound obtained from early recording, simultaneous recording and later recording is recorded on many magnetic films or tapes as data. The sound recorder makes mixed recording according to the projected picture content and creative purpose, and records it into a synthetic sound tape. In order to print and copy, we need to convert the sound from the magnetic film on which the synthetic vocal cord is recorded to a photosensitive vocal cord negative, and finally print this vocal cord negative together with the picture negative onto a positive film to become a reproduction of the unity of sound and painting.

Article source: Jiangmen recording production http://www.sjttv.com