The Rule of Thirds is a basic principle that helps you to compose interesting and balanced shots.
Imagine that the image is divided into 9 equal segments (tic-tac-toe) by two vertical and two horizontal lines.
The Rule of Thirds suggests positioning the most important elements along these lines, or at the “points of interest” where they intersect.
Doing so will add balance and interest to the photo.
When in doubt, DON'T center your subjects.
The composition on the left is perfectly centered on the dune.
Using the Rule of Thirds, the crest of the sand dune is placed on the intersection line creating a more visually interesting image.
The horizon is also placed along the top horizontal line emphasizing the size.
Studies have shown that when viewing images that peopleʼs eyes usually go to one of the intersection points most naturally rather than the center of the shot
It's a good idea to position people off to one side of the frame. This provides some "breathing space", shows the subject's environment, and stops the photo from looking like a mugshot.
We are naturally drawn to people's eyes. Place them at one of the intersections on the rule of thirds grid to give the shot a clear focal point.
Vertical subjects such as this lighthouse can split a photo in two
To avoid this, position them off-center in your composition.
When photographing moving subjects, position them as normal, but also pay attention to the direction they're moving.
As a general rule, you should leave more space in front of them than behind, to show where they're going.
Many photos will have horizon lines, and because a horizon line is a strong line, this should be placed either at the bottom or at the top of a frame as seen in the examples below. The horizon line also needs to be leveled (i.e. do not tilt the horizon line).
In the photos below, placing the horizon line at the bottom emphasizes the sky. Placing it at the top emphasizes the water.
Left: This shot lacks impact due to the placement of the diver. The Rule of Thirds can definitely help this image.
Middle: This crop places the diver onto the one of the intersections. It also places one of the sharks on the upper left intersection, which also happens to be the direction of the diver’s gaze. All of these changes strengthen the shot.
Final shot - Right: Here is the cropped ‘final’ version after applying the Rule of Thirds. Compare it to the first version.