The Earl Theisen collection spans the years 1773-1935 (bulk 1895-1934) and encompasses 1.0 linear foot. The collection consists primarily of correspondence and subject files relating to the early history of the cinema. The correspondence files contain letters from such early pioneers as inventor W. K. L. Dickson, inventor Thomas Armat, cinematographer G. W. Bitzer, inventor and film executive Leon Gaumont, inventor C. Francis Jenkins, and inventor and director-producer Louis Lumière. Of special interest is a letter from Dickson with his original drawing of the Black Maria, the first film studio. The subject files contain material relating to the early silent period, including a great amount of U.S., French, British, and German patent information. Among this material is a celluloid record for a 1912 talking picture of Edward H. Amet, a program for THE CLANSMAN (later THE BIRTH OF A NATION), animation cels by animator and producer Walter Lantz, and extensive patent information for Jean Le Roy. There is also a small number of books, magazines, and pamphlets. There is no information about Theisen's life and career.

The photograph series of the Earl Theisen collection spans the years 1895-1935 and encompasses approximately 3 linear feet. The series consists entirely of motion picture film-frame specimens. The specimens are numbered, and the collection is arranged in numerical order. The film frames, numbering in the hundreds, document a wide variety of formats in relation to image size, sound on film, and color processes. The specimens were collected by Theisen in the 1920s and 1930s, and they reflect his interest in film technology, cinematography, and film stocks. Some are copies the library made from originals Theisen collected for the Los Angeles Museum, now known as the Natural History Museum of Los Angeles County. The film frames, many of which are nitrate, have been copied to safety black-and-white negative, color negative, color transparency, or 35mm color slide film. Reference prints have been produced and are included in the collection.

Several early pioneer motion picture companies are represented, including extensive coverage of the Edison and Lumière companies. Some 19 different film gauges ranging from 8mm to 85mm, more than a dozen sound recording processes, and more than 50 types of color processes can be found. Many of the frames are extremely rare, such as 66mm film used in the earliest days of the Biograph Company in 1896, Handscheigl color frames from "Greed" (1924), and Lee DeForest's Phonofilm, an optical sound-on-film system dating from 1921. Individual specimens of special interest include those for the Lauste process for recording sound on film, dating from 1906 and 1911-1912; and a lap-dissolve accomplished inside the camera, on one piece of film, executed by the Gaumont Company in 1912.

Special effects are illustrated by the Peterson stereo effect, in which a mirror inside the camera resulted in a double image in the frame; an unidentified Georges Méliès frame depicting what appears to be disembodied heads resting on tabletops; and numerous examples of glass shots from the early 1920s. Glass shots—in which glass paintings were combined, by using a matte, with live action in the frame—were generally used to enhance a location or increase the size and scope of a set on screen.

Several frames are from one of the first animated films, J. Stuart Blackton's "Humorous Phases of Funny Faces," released by Vitagraph in 1906. Evidence of an early form of film piracy can be found in an original Lumière strip and unauthorized copy from the 1890s. Pathé Chrome frames exhibit hand and stencil coloring of exceptional quality used by the Pathé Film Company, circa 1900. Finally, there is good representation on several producers of early animation, with coverage of Walt Disney films from 1928 to 1933.

Earl Theisen (1903-1973) was born in Denver and educated in Chicago and Los Angeles. He entered the film industry in 1922 when he took a job with the Alexander Film Company. He left Alexander for Consolidated Film Company. In 1931 he began researching early cinema history and collecting artifacts under the auspices of the Los Angeles Museum, today known as the Natural History Museum of Los Angeles, and the Society of Motion Picture Engineers. He later became associate editor of "International Photographer," lectured at the University of Southern California, and became the West Coast representative for the Register Tribune Syndicate and a photographer for "Look."