For preservation of the film and also artistic value and cost in multiplication for distribution, an understanding of a foreign film is the dialogues subtitles.
Subtitle may be made by different technologies, each involving the advantages and disadvantages. The trend in recent years is, however, orientated to materials and digital processes.
Chemical process consists of applying a thin layer of paraffin wax mixture on film. Then a metal cliché that mold is removed without affecting the emulsion coating. Then attack with a chemical solution to the emulsion so unprotected, then after removal of metallic silver letters remain.
If you are processing a movie from VHS and use vhs to dvd the subtitle will be included too.
Photographic process which means copying the intermediate negative or positive copies of film dialogues pending. It is a process quite economical and productivity can be copied on the machine running continuously. For readability, usually have a black outline letters.
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