Which innovative technique did Gance introduce that would influence future filmmaking?

Gance's introduction of Poly-vision, which involved displaying the film on three screens, marked a significant innovation in the way films could be experienced by audiences. This technique expanded the visual scope of cinema, allowing for a more immersive and engaging storytelling experience. The use of three screens created a vast panoramic view that enhanced the emotional impact of the narrative, providing a sense of grandeur and spectacle. This approach not only pushed the boundaries of visual storytelling at the time but also inspired future filmmakers to explore multi-screen presentations and immersive environments, demonstrating how innovative techniques can shape the evolution of cinematic experiences.

The other options, while representing important developments in film history, do not relate directly to Gance’s innovative contributions. Sound synchronization and color grading became essential components of filmmaking later on, and vertical synchronization of images is not a technique associated with Gance’s groundbreaking work.