After Effects: create slow motion
Slow motion is a good way to highlight video clips. With the professional software After Effects you can create them quite simply. There are several ways that we present you in this article.
Slow motion with After Effects: 1. Time stretching of the video
The easiest way to slow down the normal playback speed: The menu "Time expansion". With a percentage value you simply change the original speed.
- After adding a video to your composition, right-click on it.
- In the context menu, select "Time" and then "Time expansion ...".
- Now enter any value. If you set the factor to 200%, for example, the playback speed is halved, doubled at 50%. You can also enter a negative number, then the video will run backwards.
2. Slow motion effect: time distortion of a film
For more freedom in adapting your video file, activate the time distortion. Here you can shift the original time by individual frames (pictures) using keyframes:
- Right click on your video to open the context menu.
- Here, click on "Time" and then "Activate Time Distortion". Alternatively, press the key combination [Ctrl] + [Alt] + [T].
- The line "Time distortion" now appears under your video in the composition window; the stopwatch icon should already be activated so that you can set keyframes. Now any number of keyframes (represented by diamonds) can be defined and moved to the left or right. If you move two keyframes closer together, the video will run faster if you increase the distance, but more slowly.
- If you only want to slow down a section of the video, be sure to mark and move the keyframes after this point as well. Otherwise the time will be stretched at the beginning, but the video will run faster from this point on.
3. Possibility for the slow motion effect: frame cross-fading for smooth video
Especially if you want to get more pictures out of a video than the camera has recorded, the video in slow motion quickly becomes jerky. The film needs at least 24 FPS (frames per second) for our eyes to perceive it smoothly. For slow motion, the original video should therefore be recorded with at least 50 FPS in order to display it smoothly at half the speed. If your camera does not cope with this or even 50 frames per second are not enough, After Effects offers a clever tool that calculates the missing images:
- In the composition there are several squares to the right of the file name, with a film strip over one. Click in this box until either a diagonally solid line or a dotted line appears. Alternatively, you can also select both by right-clicking on the file and then using "Frame Blend".
- The continuous line stands for pixel motion. Only the changing parts of the image are calculated and a kind of veil is created around the object. Overall, however, fewer resources are used when rendering and the overall picture looks calmer.
- If you select the dotted line, the frame mix is activated. Here, transitions between the entire images are calculated. The overall picture appears somewhat blurred and is particularly recommended for a higher starting FPS number. Accordingly, the rendering takes longer.
In this practical tip, you can read how to add further effects to your composition. A good camera for slow motion pictures is, for example, the GoPro action cam, with which you take up to 240 pictures per second. If these still jerky, you will find a solution here: GoPro video jerky - what to do ?.