A childhood belief about cartoons

My favorite and most elaborate childhood belief went like this. I knew that cartoons were draw one frame at a time, like in a flipbook. I had also seen famous paintings like the Mona Lisa. I had noticed that those paintings were more realistic than cartoons, and that the figures did not have a clear definite outlines drawn around them, whereas in cartoons they did. So, my childhood belief was that regular movies too were painted one frame at a time, just like cartoons were, but without the cartoony-looking thick outline around the figures. I couldn't wait to grow up so that I could paint my own movies. I don't remember how old I was when I learned or figured out the truth.