Effective expression requires clarity about what you are expressing. For example, this photo by the great French photographer Henri Cartier-Bresson. The interesting thing is how the apparent awkwardness of the shot, with one leg awkwardly cut, is key to its subject, which is a boy in the street, not just the boy.
C-B was making a choice. He could have pointed the camera down to get the foot, but if we add enough space at the bottom of the frame to catch the right foot, and take the same amount off the top to keep the proportion of the 35mm negative, we see how different the photo would have been. What we would have is merely a photo of two cute kids. It’s the context of street, of cars, of people, some noticing the boy and others not—the world around the kid—that gives his joie de vivre its punch. Keeping the viewpoint at an adult’s eye level so that we see the street beyond includes the kid but doesn’t make him the whole show. He shares our world, which is C-B’s actual subject.
Of course, as an abstract, formal matter, including the leg wouldn’t have been a bad choice. A large, calm area of pavement leading up to the boy’s middle-tone clothes merging with the building behind, and then the girl’s dark skirt rhyming the bottles—as a formal matter, pretty elegant. But C-B wasn’t doing abstraction, he was doing humanity. The busyness of it, the complexity, is what makes it so compelling.