The rule of thirds is a "rule of thumb" or guideline which applies to the process of composing visual images such as paintings, photographs and designs. The guideline proposes 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.^{[citation needed]}

The photograph to the right 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 tree sits at the intersection of two lines, sometimes called a power point or a crash point^{[citation needed]}. Points of interest in the photo don't have to actually touch one of these lines to take advantage of the rule of thirds.^{[citation needed]} For example, the brightest part of the sky near the horizon where the sun recently set does not fall directly on one of the lines, but does fall near the intersection of two of the lines, close enough to take advantage of the rule.

Joe McNally (1952—) is an American photographer who has been shooting for the National Geographic Society since 1987.^{[dead link]}

McNally was born in Montclair, New Jersey. He received his bachelor's and graduate degrees from the S. I. Newhouse School of Public Communications at Syracuse University. He is based out of New York City and resides in Ridgefield, Connecticut.

From 1994 until 1998 Joe McNally was LIFE magazine's staff photographer, the first one in 23 years. His most well known series is the "Faces of Ground Zero — Portraits of the Heroes of September 11th", a collection of 246 giant Polaroid portraits shot in the Moby C Studio near Ground Zero in a three-week period shortly after 9/11. A large group of these life-size (9' x 4') photos were exhibited in seven cities in 2002, seen by almost a million people. The exhibit and the book, printed by LIFE, helped raise approximately $2 million for the 9/11-relief effort.

McNally has contributed for the National Geographic magazine for 20 years. One of his photographic projects for the magazine was "The Future of Flying," a 32-page cover story, published in December 2003, commemorating the centennial observance of the Wright brothers' flight. This story was the first all digital shoot for the magazine. This issue was a National Magazine Award Finalist, and one of the magazine’s most popular covers.