Like a piece of music, a painting has to be composed. Amateur painters often give little or no thought to composition, being instead obsessed with recording exactly what they see. Artists work differently, they tend to interpret what they see and consciously or intuitively, compose their paintings even if it means manipulating the scene or objects they are working from so that the final painting looks balanced. A good example of this is the painting, Flatford Mill 1817, by John Constable.
The painting has been composed using a compositional method called the Golden Section, which was invented by the Ancient Greeks. The whole painting, including the flow of the river and even the angle of the branches on the trees, are subjected to the constructs of the Golden Section. You will see the Golden Section influencing the composition of many paintings both old and new. It influences design in many walks of life outside of art, including architecture and even the shape of TV screens.
Angles are often important in paintings they can lead the eye in a particular direction to something the artist wants you to focus on. Or they can suggest stability when horizontal or vertical lines /elements such as trees, poles, streets etc. predominate. Stability, can be used to suggest calm or solitude.
The triangle is another compositional tool used to create stability> It is often used in portraits where the head is at the apex and maybe a folded arm forms the base of the triangle. Triangles can be used to group figures often with the most important being at the apex of the triangle. A good example of this is Édouard Manet’s painting, The Balcony 1868. Religious paintings often feature Christ at the apex of the triangle, surrounded by subordinate figures at the base.
If the angled lines cross each other, this creates instability and therefore can be used by the artist to create a sense of drama, action or conflict.
In artist speak composition is the process of arranging and organising the elements of Form in order to produce a conceptual unity.