Hey,   I was reading through Kodak's 'The Essential Reference Guide for Filmmakers' and came across the following: A word about film speeds You probably know that motion picture films use exposure index (EI) to indicate speed. Although similar, EI is not the same as the ASA or ISO speed used for still films. EI denotes a somewhat conservative figure related to the higher quality requirements of motion picture film that must be projected onto a large screen. Typically the EI speed is about