A film base is a transparent substrate which acts as a support medium for the photosensitive emulsion that lies atop it. Despite the numerous layers and coatings associated with the emulsion layer, the base generally accounts for the vast majority of the thickness of any given film stock. Historically there have been three major types of film base in use: nitrocellulose (cellulose nitrate), cellulose acetate, (cellulose triacetate, cellulose diacetate, cellulose acetate propionate, and cellulose acetate butyrate), and polyester (polyethylene terephthalate (PET) (Kodak trade-name: ESTAR)).

Nitrate film base was the first transparent flexible plasticized base commercially available, thanks to celluloid developments by John Carbutt, Hannibal Goodwin, and Eastman Kodak in the 1880s. Eastman was the first to manufacture this for public sale, in 1889. Unfortunately, nitrate also had the drawback that it was extremely flammable (being essentially the same chemically as guncotton) and decomposed after several decades into a no less flammable gas, leaving the film sticky and goo-like (and ultimately dust).

A film, also called a movie or motion picture, is a series of still or moving images. It is produced by recording photographic images with cameras, or by creating images using animation techniques or visual effects. The process of filmmaking has developed into an art form and industry.

Films are cultural artifacts created by specific cultures, which reflect those cultures, and, in turn, affect them. Film is considered to be an important art form, a source of popular entertainment and a powerful method for educating – or indoctrinating – citizens. The visual elements of cinema give motion pictures a universal power of communication. Some films have become popular worldwide attractions by using dubbing or subtitles that translate the dialogue into the language of the viewer.

Films are made up of a series of individual images called frames. When these images are shown rapidly in succession, a viewer has the illusion that motion is occurring. The viewer cannot see the flickering between frames due to an effect known as persistence of vision, whereby the eye retains a visual image for a fraction of a second after the source has been removed. Viewers perceive motion due to a psychological effect called beta movement.

Base or BASE may refer to:

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