It was always possible to play with the speed of film on analog editing systems, though limitations of the technology meant that if you slowed anything down too much, the frame rate at which it had been shot could become apparent and the image quality would start to suffer. As a result, shooting in slo-mo on film meant shooting at a higher frame rate to ensure that the end results looked good. Also, conventional sound recordings associated with slowed down or sped up footage could suffer from becoming too high or low pitched, which wasn’t always desirable. Digital systems afford us much greater flexibility and computers are good at “filling in” and manipulating material to enable subtle or extreme speed changes to be performed with no ill effects. In Premiere, working with speed is pretty straightforward.
With a clip in the project bin you can right click on it and select the Speed / Duration option. The simplest way to affect a clip before placing it into a project is to manually enter a percentage speed value or a time duration in this box.
Clicking “Reverse Speed” will reverse both the audio and video, but maintain the clip’s original speed and duration.
If you choose to make a clip faster or slower, you can click the Maintain Audio Pitch checkbox to ensure that the audio associated with the clip doesn’t pitch up or down but is timestretched along with the clip.
The same thing can be performed on a clip when it is already in the timeline by right-clicking on it and choosing Speed / Duration again. This affects only the instance of the clip in the timeline, not the master clip in the project bin.
To manually stretch a clip on the timeline, for example to make it occupy the space up to the next clip, first ensure that snapping is on by checking in the Sequence > Snap menu option—or leave it off for freeform stretching. Then go to the Tool palette and choose the rate Stretch tool or press the X key as a shortcut.
Move the mouse over either the left or right edge of your clip and drag it to make it longer or shorter. The clip will update with a percentage speed value to show how much it has been changed by. It should play back without rendering, but to lessen the CPU load you can render the modified clip down.
Double-click on a clip to open it in the viewer and enter its Effect Controls section. Under the Time Remapping section you can click to add keyframes and change the speed value over time. Use the handles to create speed ramps, or create straight jumps so the speed changes instantly.
Render the effects in the work area so that your Mac is not too heavily loaded while playing back and you can continue experimenting with video playback speed!