The rule of thirds is a compositional rule of thumb in visual arts such as painting, photography and design. The rule states that an image should be imagined as divided into nine equal parts by two equally-spaced horizontal lines and two equally-spaced vertical lines, and that important compositional elements should be placed along these lines or their intersections. Proponents of the technique claim that aligning a subject with these points creates more tension, energy and interest in the composition than simply centering the subject would.
The photograph below demonstrates the application of the rule of thirds. The horizon sits at the horizontal line dividing the lower third of the photo from the upper two-thirds. The rock sits at the intersection of two lines, sometimes called a power point. Points of interest in the photo don't have to actually touch one of these lines to take advantage of the rule of thirds.
The principles of the rule of the thirds
The rule of thirds is applied by aligning a subject with the guide lines and their intersection points, placing the horizon on the top or bottom line, or allowing linear features in the image to flow from section to section. Using any compositional guidelines inflexibly is generally discouraged, as there are many situations in which they are best ignored; the main reason for observing the rule of thirds being to discourage placement of the subject at the center, or prevent a horizon "dividing the picture in half".
When photographing or filming people, it is common to line the body up with a vertical line, and having the person's eyes in line with a horizontal one. If filming a moving subject, the same pattern is often followed, with the majority of the extra room being in front of the person (the way they are moving).
