Complex sentence: The gun, capable of capturing 12 frames per second, produced images from which Marey deduced that as the cat had no rotational motion at the start of its descent the cat was not "cheating" by using the cat handler's hand as a fulcrum.
Split into simpler sentences: The gun, capable of capturing 12 frames per second, produced images from which Marey made some important deductions. Namely, that as the cat had no rotational motion at the start of its descent the cat was not "cheating" by using the cat handler's hand as a fulcrum.