The 180 rule is essentially this: In any scene, an imaginary line can be drawn in the centre of the filming area, which divides it into two equal parts. You cannot change to another camera if you overstep this imaginary line. * You may not have thought this to be the case before, so take a look at any film you wish in order to research the 180 rule. So, why does this rule exist? * Continuity As the topic right now is continuity, a range and rhythm of shots is defined to be continuous (unless it isn't!) In order for us to maintain a sense of space and perspective, the camera cannot be allowed to constantly throw around our ideas of such spatial use. * Consistency Continuing from the above point, the change of camera must be seamless, in order to stop our ideas of the visual space from being disrupted. * Consider two people walking towards each other, as in the diagram above of A and B. There are cameras just over the shoulders of A and B, on the same side of the line. However, imagine if the camera which is on person A is not camera 1 but camera 2, crossing the line. We then have to get used to the other half of the space around the people. We would then have to be aware of the whole area around A and B, and to be readily aware to accept both on-screen. So, what the 180 rule also helps to do is to minimise the amount of space we see, speeding up the process of perception and helping to concentrate on a specific visual area. It also helps us in perception of other features of continuity editing, such as eyeline match, and shot/reverse shot. * The 180 rule is, however, a general rule of thumb. It applies more to indoor shooting than on location. Location shooting often increases the rule beyond 180, as we can take in more of the environment. * This rule goes hand-in-hand with the rule of perception in editing: The minimum change of camera angle in two different shots to avoid confusion is 30.