What invention by Eastman had a large impact on the motion picture industry?

The invention of flexible roll film by George Eastman was a pivotal advancement for the motion picture industry. Before this innovation, film was typically available only in rigid sheets, which made it cumbersome for filmmaking. Eastman's flexible roll film revolutionized the ease of capturing motion by allowing filmmakers to shoot continuous footage in a portable manner. This accessibility not only simplified the process of filmmaking but also enabled the creation of longer, more complex narratives. As a result, it played a crucial role in the establishment and growth of the motion picture industry, facilitating the production of movies on a much larger scale than had previously been possible.

The other options, while significant in their own right, do not capture the same foundational impact on the motion picture industry. For instance, the instant camera and digital camera are more relevant to photography rather than the development of cinema, and while the film projector is important for displaying films, it is the flexible roll film that fundamentally changed how films were made in the first place.