In photography the Rule of Third refers to the guidelines which are used while taking photographs which allow for more accurate shots. These guidelines divide the image into thirds by two equally spaced horizontal and vertical lines, which makes the image much more pleasing to look at whilst the lines are present.
This is an example of how the guidelines will appear on a camera. As you can see they allow for you to centre the image as well as allow for you to have both foreground and horizon to a picture of a landscape. Points of interest commonly occupy the squares made by the lines.
Here is an example of the same image without the rule of third applied. Without the rule applied it is harder to analyse each section of the image; the image also appears to have less consistency and doesn't flow as well.
Side by side comparison between an image using the rule of third and an image not using the rule.
The Rule of Third is related to the Fibonacci Spiral; which is created by drawing a spiral and then adding lines into the spiral. This creates squares in the spiral with sizes which start large and gradually get smaller.
The Fibonacci Spiral uses the Phi number (more commonly known as The Golden Ratio) which is rounded to 1.618.
The Fibonacci Spiral uses the Phi number (more commonly known as The Golden Ratio) which is rounded to 1.618.