Canon EOS-3 Instructions Manual page 27

Custom Function CF-3 can prevent the ISO film speed from being set
CF
automatically. See page 108.
Since an infrared sensor is used to detect
the film's transport, it will fog (expose)
infrared film below the picture area.
Basic Terminology 1
● ISO film speed
The ISO film speed indicates the
film's sensitivity to light. The higher
the film speed, the more sensitive
the film is. The more sensitive the
film is, the less light is required to
obtain a standard exposure.
Therefore, a high-speed film is
suited for low-light situations. The
ISO film speed is standardized by
the International Standardization
Organization (ISO). The EOS-3 can
display a film speed from 6 to 6400.
Loading Film
27