Composition is one of the hardest things to grasp and is subject to more than its share of ridiculous theories. Even defining composition seems to cause controversy. There is formal composition, informal composition, dynamic, intuitive, and classical composition.
To help clear the field let’s start with the basic idea of what composition is. Composition is the placement of shapes of color and value within the four corners of the canvas. The goal is to focus your eye where the artist wants it to go. I submit the only thing you must remember is good compositions do this, bad compositions don’t.
To get the viewer to look where you want them to a number of tried and true formulae have been employed by artists for centuries. One of the oldest is based on the golden section or golden mean. This idea was used by the Greeks in their buildings. It is an observed proportion found in many natural things. Its mathematical ratio is 1 to 1.618. You can see it in the veins of leaves the volumetric curves of a seashell. It is repeated in division of your joints in your fingers and the ratio of the length to width of your hand.
The golden section is a perfect proportion and creates unity within a picture when applied.
The formula is AB is to BC as BC is to AC or the smaller is to the greater as the greater is to the whole.
There is even a sequence of numbers that relate to this concept, the Fibonacci sequence. The first number of the sequence is 0, the second number is 1, and each subsequent number is equal to the sum of the previous two numbers of the sequence itself; the first ten numbers look like this
An image of the sequence looks like this.
As you can see it makes it easy to decide how and where to place your center of interest. If you plot out the growth of the sequence you get a spiral. Secondary interst can be placed along the path to create movement throught the picture.
Some artists even go so far as incorporating the width of the frame as part of the design sequence. However far you take it, the golden section is a compositional guide that has stood the test of time.