Abstract: In the embodiment of the film canister described in the specification, a motion detector detects rotation of a roller each time film is withdrawn from the canister and supplies a corresponding signal to a microprocessor. Since the same length of film is withdrawn each time film is used by the COM system in which the canister is mounted, the microprocessor can determine the total length of film withdrawn from the number of film motion signals it receives. The microprocessor deducts that length from the original film length in the roll to provide an accurate indication of the current length of film stored in the canister. The canister also includes data entry keys and a display panel for displaying information about the type of film in the canister and the remaining film length. In addition, the microprocessor generates signals corresponding to the rate of film roll rotation as the film is withdrawn from the canister for use with various COM systems.