Art composition rules provide a starting point for deciding on a composition for a painting, for deciding where to put things. The Rule of Thirds is the easiest art composition rule to follow in a painting. It's a basic rule, popular among photographers, but equally applicable to the composition of paintings. Applying the rule of thirds to a painting means you'll never have a painting that's split in half, either vertically or horizontally, nor one with the main focus right in the center, like a bull's eye.
Quite simply, divide a canvas into thirds both horizontally and vertically, and place the focus of the painting either one-third across or one-third up or down the picture, or where the lines intersect (the red circles on the diagram).
Take a look at these two photos of a lion. On the one on the left, your eye is drawn straight into the center of the image and you tend to ignore the rest of the picture. On the one on the right, where the lion's face is on one of the Rule of Thirds 'hotspots', your eye is drawn the the lion's face, then around the painting following the curve of the body.
Until you're confident mentally visualizing the lines, draw them in lightly on your canvas or piece of paper with a pencil so you can easily check that the placement of the elements in your painting adheres to the Rule of Thirds. If you do thumbnail sketches first, draw the thirds grid on top to check the composition.
One of the first things to decide in a composition is how many elements or items there will be in it. And one of the simplest ways to make a composition more dynamic is to have an odd number in the composition, say three, five, or seven, rather than an even number, say two, four, or six. It's called the Rule of Odds.
Having an odd number of things in a composition means your eye and brain can't pair them up or group them easily. There's somehow always one thing left over, which keeps your eyes moving across the composition.
With an even number of elements, such as in the basic composition shown in the top image, your eye instinctively pairs up the trees, whether it's two left and two right or two top and two bottom. Whereas the lower two compositions, each with an odd number of elements, are more dynamic in terms of composition because your brain can't pair up the elements.
Why do we pair things up naturally? Perhaps it's because our body is designed in pairs: two eyes, two ears, two arms, two hands, and so on. (Okay, we've only one nose, but it's got two nostrils!)
No, whether it's bottles, apples, trees, or people, the same Rule of Odds applies. Of course, the number of elements is not the only thing to consider in a composition, but it's essential and quite a good starting point for developing a painting.
If I asked you to count the number of brushes in the left-hand photo, you'd be able to do so quickly. In the right-hand version of the painting you'd have to spend a little longer and, ultimately, may be uncertain because some of the brushes are hidden behind others.
In these two photos from a work-in-progress, the left photo shows the brushes in the container as I initially painted them. Stepping back a little later to assess what I'd been doing, I realized that I'd made a neat and tidy arrangement: two tall brushes and four shorter, all equally spaced. How boring to look at. One glance and you've taken it all in.
Whereas on the version of the painting on the right, I've added several more brushes of varying heights and angles. It's far more interesting to look at, it engages your attention and keeps you looking for a while, which is what a painting's composition should do. It's the Rule of Odds in action.