The number of times that a shot occurs. This is an excellent mechanism for building up tension. Frequency is also to do with temporal relations, in that a shot is allocated a certain number of 'runs' until it is succeeded. The length of the shot. Duration does not necessarily mean that that particular scene has passed - a take could perhaps be repeated again, shot from a different angle.
Duration is an excellent tool to play around with.
A personal experience of this is when I watched Martin Scorsese's Taxi Driver with my sister. However, the camera was still there. She began asking why the shot was going on for so long. Thus, duration is a powerful tool that can make viewers become aware of not only the situation, but also of the camera. Task - Consider the differing durations in shots between fictional and factual film.