3 Introduction to Expanding and Compressing Time
One of the functions of editing is to manipulate time. An editor will often need to do this so the viewer will not have to witness every second of the action in order to get an appreciation of a chain of events. For example, in a wedding ceremony the couple may be seen leaving the altar and heading towards the registry desk to sign the certificates. The scene could logically cut to them actually signing the certificate without the need to show their journey to the registry desk.
Also, long passages of time may be signified by a fade to and from a blank screen. The use of a close-up shot followed by a change in time and location can also achieve the same effect. In dramatisations, the editor may want to express extreme manipulations in time, which can be achieved with a combination of close-ups, dissolves or fades. Reverse transitions in time are often achieved by using ripple dissolves or other effects and are often used to demonstrate that a character is remembering something from their past.
3.1 Playback Speed & Direction
‘Slow motion’ is used for a number of reasons. In practical terms, slow motion can be used to show detail in a fast moving subject. In creative terms, slow motion can be used for dramatic effect; it is often used for its romantic quality and there are certain scenes in a wedding video which lend themselves perfectly to slow motion treatment.
In practical terms, ‘Fast motion’ (or ‘Accelerated motion’) is used to reveal an otherwise imperceptible development in a slow-moving or gradually-changing subject. For example, time-lapse images or speeded-up footage of a building being constructed gives the viewer an appreciation of the progress of the build. In creative terms, fast action can add humour to a sequence, or heighten the thrill of speed in footage filmed from a moving vehicle.
Reversing the motion of footage is generally only used for surreal or comic effect, but can also be used to explain an event to the viewer. However, slow, fast and reverse motion effects are generally used creatively to make normal or familiar action look strange or unusual. Indiscriminate or overuse of these effects is likely to confuse the viewer.
3.2 Freeze Frame
Like slow motion, freezing the action is used to show detail in a moving image. However, to create a clear ‘Freeze Frame’ in video will require consideration at the filming stage, especially when the subject is moving at speed.
Interlaced video is either 25 frames per second for PAL or 30 frames per second for NTSC. These frames are made up of two interlaced fields, which are perceived as one image to the human brain. Freezing a single frame will show the movement of the subject between the two fields as a juddering or flickering effect, so it is important to ‘de-interlace’ the fields to show a static image. However, with a fast moving subject this image will still appear blurred. To overcome this, the original footage will need to be filmed using a fast shutter speed setting – or by using a camera that films in progressive mode.