There are lots of "rules" to think about when composing an image. At its simplest, effective composition is mostly about arranging shapes. When you are thinking about a composition in front of your camera, it helps to remove the labels and view the scene in terms of just those shapes: the "shapes" that make up an image are the elements of visual design: line, shape, form, texture, pattern and colour. Looked at this way, even a simple pastoral scene of cattle grazing in a field becomes an exercise in those elements. of line and shape, of pattern and repetition, and of balance using visual weight.
Tree trunks become a repeated pattern of lines, the curve of a hillside is repeated in the arrangement of animals along the hillside and in the curve of the fence which must also follow the curve of the hill. A group of trees, leafed out in early spring foliage becomes a subtle texture composed of different shades of green. The loan animal off to itself on the lower left, since it contrasts sharply with the surrounding grass, becomes a strong draw for the viewer’s eye. Elements that draw a viewer’s eye in this way are said to possess significant “visual weight”, and in this scene the animal on the left as sufficient visual weight to help balance a composition that would be otherwise be weighted more to the right. Aside from just helping to balance the composition, the lone cow also momentarily pulls the viewer's eye way from the other areas of visual interest in the scene, causing the viewer's eye to move continuously through the composition. Creating movement in an image amplifies visual interest, and helps holds a viewer's interest longer
Effective composition is easier when we learn to let go of simply what a thing is, and concentrate on the shapes that make up our images.