It's not hard to make B&W photographic film; I have done it. But it is
extremely, extremely hard to make perfect film that is just the right
dimensions for motion picture work, has perfect perforation, no emulsion
defects, and controlled sensitivity and curve shape roll after roll.
This fine film from Kodak explains much of it:
Note that this is showing a facility that no longer exists; the current
Rochester plant deals with much much larger quantity runs and everything is
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