Learn how to speed ramp your video and how to create smooth slow motion by using Time Remapping in Adobe Premiere Pro.
There are 3 different ways that you can control the speed of your video in Adobe Premiere Pro.
Let's talk about how to use each of these options.
One of the easiest way to speed up or slow down your video is with the Rate Stretch tool. You can find this tool in your toolbar. It might be hidden behind one of the other editing tools so simply click and hold to access it.
With the Rate Stretch tool selected, simply click on the end of your clip and shorten or extend it to speed up or slow down your video.
Another option is to right click on your clip in the Editor Timeline and go to the 'Speed/Duration...' settings.
This will open up the Speed and Duration settings for the clip. In her you can specify the percentage speed of your video. You can also Reverse the video, select to Maintain Audio Pitch and Ripple Edit or Shift any clips further in the timeline.
All of the previous options affect the entire clip. If you need more control you can use Time Remapping. With Time Remapping you can create speed ramps where you ramp up or down the speed of your video smoothly.
You can enable Time Remapping by right clicking on your clip and going to Show Clip Keyframes -> Time Remapping -> Speed.
This will add a horizontal white line to the clip on your timeline that represents the playback speed. You can drag this line up or down to speed up or slow down the clip.
You can also create keyframes (with CTRL/CMD + click) and animate the speed of the clip. In order to smoothen out the transition you can drag the handles of the keyframes left and right to create interesting speed ramp effects.
When you slow down a video in Adobe Premiere Pro, you stretch out the content. Premiere Pro needs to figure out where to get the additional frames to extend your video duration.
If you want smooth slow motion you need to film your video at a high frame rate. If your clip is filmed at 60 FPS, your sequence is set to 30 FPS and you are playing your clip back at 50% speed, Premiere Pro has enough additional frames in the video to give you perfectly smooth motion.
However, if your video was shot at 30 FPS, Premiere Pro needs to figure out where to get those additional frames from to play back at 50% speed.
This is where Time Interpolation becomes important. Time Interpolation allows you to control how Premiere Pro generates the frames required to let you slow down your video.
You can access this option by right clicking the clip and going into the Speed/Duration settings.
Time Interpolation gives you 3 options.
Premiere Pro will source the frame from the video. If there are not enough frames in the video (e.g. not shot at a high enough frame rate), the nearest frame will be used. This can lead to duplicated frames and stuttering video if you slow down your video.
Premiere Pro will generate a blended frame to fill the extra space. This frame is a mix between consecutive frames in the source video. You will likely see duplicated edges and a motion trail where there is movement.
This can be an interesting effect if you want to convey the feeling of someone being a bit disoriented, drunk or zoned out.
Optical Flow looks ahead and back to guess the movement of the objects in your scene based on their pixels. Premiere Pro will try to generate frames that fill in the missing movement.
This option will look closest to true slow motion. However you may see little artefacts or glitches and it will likely not be quite as perfect as shooting your video at a high frame rate.