The usual process of film making is to shoot negative film in a camera and then make a positive print for projection. For colour slides and 8mm cine, reversal film was common:
https://en.wikipedia.org/wiki/Reversal_film This saved the cost and effort of printing from negative to positive.
Reversal processing was very rare (never done?) for 16mm and 35mm cine.
Before portable videotape equipment TV stations shot a lot of 16mm film. Mainly for news but also low budget production. For news, the time from camera to telecine was critical. So the film was routinely scanned as negative in the telecine. The reversal to positive was done by inverting the video. There are other problems to do with grading and gamma correction but these were solved.