Leading The Eye / Leading lines
Composing a picture is like telling a story—you need to connect elements together in a logical way. This is especially important if you are trying to capture a complex scene. One of the easiest ways of doing this is to provide a visual path that the viewer can follow.
This path can be as simple as a physical line within the image that links the foreground to the background. In landscape photography, if you are lucky, the scene may already contain a meandering river or a country lane that draws the eye through the picture. Since people scan images, rather than just staring at them, this provides a route for them to follow as they read your picture story.
This solution is fine for when you have a suitable stream, road, or railroad track to place strategically in the composition. But these are not available in every landscape, let alone other photographic subjects.
The answer is to use one or more diagonal lines. Diagonals can be found all around you—and can be engineered in areas where they are not obvious simply by altering the camera viewpoint—you just need to think creatively. For example, the straight lines of the front of a building can be turned into strong diagonals by getting in close and off-center—this will result in linear perspective creating converging verticals or horizontals.
The beauty of diagonals is not just that they are so easily found, and provide such a simple visual route across the picture. They also suggest a continuation beyond the confines of the image and give a feeling of movement. Strong diagonals make strong pictures, and part of the reason they have this effect is that they never run parallel with the sides of the frame.
However we shoot, show, and crop our digital images, they are almost always rectangular in shape. These four perfectly straight edges are not just boundaries to the picture—they are effectively part of the composition. If lines in the picture follow the same directions as the edges, the picture will tend to look predictable and staid. A diagonal refuses to go with the flow and so makes the composition more dynamic. With single lines, the maximum effect is achieved when the line is at 45° to the edges, and breaks into the picture at one of the four corners.