We all love the Dewey Decimal System. However, just as the world we live in changes, the Dewey Decimal System also changes over time.
At the time of the earliest editions of Melville Dewey's Decimal Classification and Relative Index for Libraries, Clippings, Notes, Etc the medium of motion pictures did not yet exist. Before an actual call number was assigned for this subject, the librarians the San Francisco Public Library invented their own solution, placing them within the Dewey number 792 - Theater, pantomime, opera.
source: Melville Dewey, Decimal Classification and Relativ [sic] Index for Libraries, Clippings, Notes, Etc., edition 9 revized [sic], (Lake Placid Club NY, 1915).
Dewey number 792 was a reasonable choice, especially given that the earliest films without sound had much in common with pantomime. Unfortunately, when the compilers of the Dewey Decimal Classification got around to including film they placed it within the Dewey number 791 - Public entertainment. Thus the San Francisco Public Library became at odds with the official Dewey Decimal system.
In the days before computers and computer networking, assigning heterodox Dewey decimal numbers was not a terrible thing. All book cataloging was done in house. As long as San Francisco Public Library catalogers knew the library's established call numbers for film there was no problem at all.
In time, the San Francisco like nearly all other libraries joined OCLC - originally the Ohio College Library Center, later the Online Computer Library Center - a consortium that created a networked, standardized, communal library catalog. This meant that member libraries could take advantage of the cataloging work done at other institutions, saving them the time and expense of cataloging each item themselves. As this happened, the San Francisco Public Library found that many of its long established call numbers were at odds with the accepted standards of the Dewey classification and the Library of Congress (a major contributor of records to OCLC). Assigning in-house numbers to these materials added to the time and expense of bringing books to the shelves.
In 1992 the Library decided to do away with almost all of our in-house practices for assigning call numbers and to follow the most recent edition of the Dewey Decimal Classification. This has meant that for many areas, books with a similar subject matter has gotten scattered across more than one call number.
Dewey Dewey Classification Summaries (OCLC website)
One of the emblematic problems we encountered after 1993 was the division of our film collection into two discrete sections.
The bottom line is: books on motion pictures prior to 1993 used call numbers 792.1 and 792.5. Books acquired after 1993 have been given the call number 791.43. (This problem is exacerbated here at the Main Library where was have so many titles, and they happen to be separated by the elevator lobby between ranges 44 and 45). This is further muddied by the fact that books related to film and video making have been assigned the Dewey number 778.5 ("Fields and Kinds of Photography) and books on the motion picture industry have been assigned the Dewey number 384.8 ("Communication, telecommunication").
The guide below gives the old 792 San Francisco numbers and their translations to current Dewey numbers. Happy browsing!
792.1 = 791.4302
Film - actors and actresses biographies
792.5 = 791.43 / 791.4309
Film history, criticism
792.5 = 791.4305
792.5 = 791.4306 = 384.8309
792.5 = 384.806-384.809
792.501 = 791.4301
792.502 = 791.4302
792.503 = 791.4303
Film dictionaries and encyclopedias
792.507 = 791.4307
792.51 = 791.4372 / 791.4375
792.52 = 791.4309
Films - historic treatment
792.53 = 778.535
Film making - editing
792.55 = 778.534
Film making - special effects
792.59 = 791.437
792.59xx - 791.4309
film - geographic presentation
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