Canon 518 Single -8 - Manual (Page 33)

Changing Films
From color to black and white film or vice versa,
the
film cartridges can be easily interchanged
any time halfway through the film. The amount
of film wasted will be approximately 12cm (4-3/4
inches), including the preceding and succeeding
parts of the film that is outside the film car­
tridge. It will be convenient to write down the
footage counter figure on the film cartridge to
be removed when changing film cartridges.