Continuity in Film: Rule of Thirds

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. This creates more tension and creates a more interesting composition rather than just putting things in the centre. Ideally, the points of interest should occur 1/3 or 2/3 of the way up or across the frame. Usually, the lower third or upper third line will be where the horizon sits, whilst the primary focus of the shot will remain on an intersection point.

The main reason for using the rule of thirds is to discourage the subject from being at the centre, or prevent the horizon from "dividing" the picture in half. When the subject is placed in 1/3 of the frame, the remaining 2/3 of the frame balances out the subject with some sort of context. This is because, if you have 2/3 of the frame to use, you can fill it with all sorts of visual aesthetics that can help aid the storyline.