When you look at this image, what catches your attention first? Is it the sky with its blue and white colours? Or is it the impressive desert landscape? Chances are you first see the car, even if it is comparatively small.

The rule of thirds (and, really, this is not a rule but rather a kind of guide) says that an image can be intersected by two horizontal and two vertical lines dividing it into nine equal parts. Important elements in the image can be positioned along these lines or where the lines cross, which has shown to be pleasing to the eye. A typical example would be placing the horizon in a landscape image one third from the bottom of the image, with greater emphasis on the sky, or two thirds from the bottom, with more emphasis on the foreground.

A viewer’s eyes are usually drawn to one of the crossing points (experiments have shown that the area that will first attract attention is the top left intersection) rather than to the centre of the image.

In the following image our attention is not primarily drawn to the cake and the other dishes on the table but to the little girl’s wistful look. The main message is not to show all the yummy things but to convey the girl’s longing for the birthday party to begin.

Even if an image is full of details, our attention can be directed towards a certain element due to its position. Here we first look at the woman dressed in black and white.

Sometimes a secondary point of interest is placed at the diagonally opposite thirds position as a counterpoint. In this image the young woman’s face is counterbalanced by the screen of her laptop.

A counterpoint can also be found in this vertical image, creating a strong link between the student and the lecturer.

Here is another vertical image with its main element in an eye-catching position.

And now it gets more theoretical…

The proportions of the rule of thirds are related to *the golden ratio*, which is a number that is calculated by dividing a line into two parts so that the longer line divided by the shorter part is equal to the whole length divided by the longer part. In mathematical language this is expressed as a/b = (a+b)/a. The result is 1.6180330887… (probably going on infinitely), usually rounded off as 1,618.

The imaginary lines of the golden ratio are a little closer to the centre of the image than the ones of the rule of thirds.

In the early 13^{th} century the mathematician Leonardo Fibonacci discovered an interesting sequence of numbers (it was actually known in India several centuries earlier). If you start with the number 0 the next number is 1. To get the next number you add the two previous ones. So in this case the next number is 1 (0+1). The following number is 2 (1+1), the one after that 3 (1+2). Then we get 5, 8, 13, 21, 34, 55, 89, and so on. An interesting fact is that the ratio between two Fibonacci numbers is very close to the golden ratio, especially with higher numbers.

There are, of course, other factors that make us notice a detail in an image, for example size, colour or contrast. And there’s a lot more when we talk about image compositon, like dynamic symmetry, negative space, proximity, figure–ground relationship, the S curve, sharpness, depth of field, etc.

There are people who argue that the rule of thirds is dead and that nobody follows it. What’s your opinion? Leave a reply below!

You can find more images based on the rule of thirds here.