Certaines observations is a two-projector-one-screen piece : the two reels -- one B/W (positive) print, one W/B (negative) print --, struck from the same negative, should be projected superimposed on a single screen. If the two projectors are not locked in sync, the projectionist may occasionally stop one of them briefly to try to keep the two pictures in sync. The person projecting may also move one projector slightly, placing the two images side by side momentarily. The two reels should be re-superimposed afterwards.

The film's title stems from Newton's Mathematical Principles of Natural Philosophy where certain observations are used to define notions regarding the appearance of things in true or apparent motion. The material was structured while filming one evening the14th July street celebrations : lights strung across the road, a band, baloons, cars, an ambulance, a horse, fireworks and people dancing on the Pont d'Avignon.