Canon VI-T - Manual (Page 27)

FILM TYPE INDICATOR
Depending on the type and variety of
film in use, the Film Type Indicator Disc
(22) is revolved with the tip of one’s
finger until the relevant indicator symbol
comes opposite the index.
Black color is used to indicate black
and white film, blue for daylight type
color film, and red to show for tungsten
color film.
This indicator also gives both ASA and
DIN film sensitivity readings.