The filmstrip was a common form of still image instructional multimedia, once commonly used by educators in primary and secondary schools (K-12), overtaken at the end of the 1980s by newer and increasingly lower-cost full-motion videocassettes and later on by DVDs. From the 1940s to 1980s, filmstrips provided an easy and inexpensive alternative to 16 mm educational films, requiring very little storage space and being very quick to rewind for the next use. Filmstrips were large and durable, and rarely needed splicing. They are still used in some areas.
A filmstrip is a spooled roll of 35 mm positive film with approximately thirty to fifty images arranged in sequential order. Like 16 mm film, a filmstrip was inserted vertically down in front of the projector aperture, rather than horizontally as in a slide projector. Therefore, the frame size is smaller than normal 35 mm film. Two image frames of a filmstrip take up the same amount of space as a single 35mm frame, including its guard band, so that a 25 exposure 35mm film can contain 50 filmstrip images. Early celluloid filmstrips had a habit of melting or combusting from the intense and sustained heat of the projection lamp. These were called pictural filmstrips, the first filmstrips that were produced in a complete set.
