How to Use Optical Flow in Adobe Premiere Pro CC (2019)

Optical Flow is one of the most useful features in Premiere Pro for creating slow motion. It takes footage shot at a standard frame rate (like 24 or 30fps) and generates new frames between the existing ones. The result is smooth slow motion that looks like it was shot at a much higher frame rate. You don’t need to shoot at 120fps or 240fps to get buttery slow motion anymore. Optical Flow can fill in the gaps.

It is not perfect for every situation. Complex backgrounds and fast-moving subjects can cause artifacts. But for a lot of footage, it works surprisingly well. Today I am going to show you how to use Optical Flow in Adobe Premiere Pro CC.

Method 1: Speed/Duration

This is the quickest way to apply Optical Flow for a uniform slow-down.

1. Place your footage on the timeline.
2. Right click on the clip and select Speed/Duration.
3. Change the speed percentage to your desired slow motion amount. 50% is half speed. 25% is quarter speed. Anything below 25% may start showing artifacts depending on the footage.
4. At the bottom of the dialog, find Time Interpolation. Change it from Frame Sampling to Optical Flow.
5. Click OK. The clip will stretch on the timeline to its new, longer duration.
6. The clip may need to be rendered to preview smoothly. Press Enter on the timeline, or go to Sequence > Render In to Out.

Method 2: Time Remapping

This method gives you more control, letting you vary the speed within a single clip. You can have normal speed, then slow motion, then back to normal.

1. Place your footage on the timeline.
2. Right click on the clip and go to Show Clip Keyframes > Time Remapping > Speed.
3. Expand the clip height on the timeline so you can see the speed line (a horizontal rubber band).
4. Use the Pen Tool or Ctrl+click on the speed line to add keyframes. Drag the speed line down between keyframes to slow that section, or up to speed it up.
5. Right click on the clip and go to Time Interpolation > Optical Flow.
6. Render the timeline with Enter to preview the result.

For a deeper dive into speed ramping with Time Remapping, check out the slow motion tutorial.

When Optical Flow Works Well

• Simple backgrounds. A subject against a clean, uncluttered background gives Optical Flow the best conditions.
• Steady camera. Handheld footage with lots of shake creates more artifacts.
• Moderate slow-down. 50% speed works great on most footage. Going below 25% pushes the algorithm hard and artifacts become more likely.
• Green screen footage. Solid color backgrounds are ideal. You can slow footage to 5% or even 1% on a green screen with near-perfect results.

When It Struggles

• Complex, detailed backgrounds. Trees, crowds, and busy scenes can cause warping and ghosting.
• Fast-moving subjects crossing each other. Multiple subjects moving in different directions confuses the frame generation.
• High contrast edges. Strong edges between bright and dark areas can show visible artifacts.

Tips

• Always render before judging. Optical Flow looks terrible in real-time preview. It needs to be rendered to see the actual result. Press Enter and wait.
• Frame Blending is the alternative. If Optical Flow creates too many artifacts, try Frame Blending instead. It is less smooth but more reliable. You can set this in the same Time Interpolation menu.
• Combine with reverse speed for slow-motion rewind effects. Set the speed to -50% with Optical Flow for a smooth slow-motion reverse.
• Shoot at a higher frame rate when possible. Optical Flow is a great tool, but real high-frame-rate footage (60fps, 120fps, 240fps) will always look better. Use Optical Flow as a backup when high-fps footage is not available.

That is how you use Optical Flow in Premiere Pro. It is a powerful tool for creating slow motion from standard footage, and when the conditions are right, the results are excellent.