You’ve seen it before in the movies: one person shoots at another person then time suddenly slows down to an excruciating rate. Sometimes it can be employed in a number of different ways to emphasis a particular moment in time where traditional timing and pacing methods couldn’t capture it as nicely. This technique is often called “slow motion” or “retime.” Essentially you are slowing down a video to half or more the rate it would normally progress.
You can do a lot of interesting things with slow motion footage. A video artist named Bill Viola and Douglas Gordon play a lot with this technique and how time visually works. I shot a video recently in the style of Bill Viola. Viola employs a lot of slow motion footage to emphasis a lot of his spiritual and mystical themes. I’m going to take you through my process as to how I did my video which you can watch below.
1) Select the slip you are going to retime.
Normally you wouldn’t want to retime an entire clip unless that was your goal. You can cut a section out of your video to retime to, again, add emphasis to a particular moment in time.
2) Select the amount of retime.
You can select the retiming tool in the middle right hand side of the FCPX window. You have a few options to slow your clip down or speed it up. For mine I chose a custom speed of slowing it down to 2% of its normal speed.
3) Customize your retime.
Sometimes you don’t want to slow down to 50%. You might want to bring it down to 40%. How many frames per second (fps) you shot in will depend on how much you want to slow it down. For the standard 24fps, you wouldn’t want to slow that down too much unless you’re looking for quality loss. If you shoot in 60, 120, even 200fps, you can grab even the tiniest of details by slowing it down to 30, 20, even 10% of your clips original speed.
To customize you can drag the little icon on your clip in the timeline right or left depending on how fast or slow you want your clip.
4) Choose your method of retime
FCPX gives you three options when you’re retiming. Normal, Frame Blending, or Optical Flow. Say you chose “Normal” for your retiming and slowed your clip down to half its speed. In a 24fps video, you would only show 12 of those frames in one second. This makes your video look choppy.
In “Frame Blending,” FPCX essentially blends two frames together, which is helpful at speeds above 50%. However, it is a much less sophisticated technique compared to “Optical Flow.”
I love using “Optical Flow” because it just looks so good. A writer for FCPeffects.com writes, “Optical flow works by creating frames in between the actual frames of your footage. Instead of repeating frames or blending them together, FCPX creates new frames based on the content of your footage, thus making playback crisp and smooth.”
“Optical Flow” is obviously the smoothest of the bunch. But it can add an interesting effect to your video if employed for an extended period of time.
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