Converting 60p or 30p footage to smooth 24p: a quick guide

Shooting

During production, if you are sure you don’t want to do slow motion, set your shutter speed manually to 1/50 or 1/40.  This will greatly smooth the footage when converting to 24p.

Post Production: Importing footage

Though Final Cut Pro, FCP X, Premiere, and Vegas use different interfaces, the principles remain the same.

  • Set up a project with a 24p timeline.
  • I’m assuming you’re shooting AVCHD, which is the standard format for most non-24p cameras.  In FCP 7, import using Log and Transfer.  In FCP X, use the Import tool when you connect the camera or card to the computer.  In Premiere, you choose the Private folder from your Media Browser, or find it via File > Import.
  • Transcode/proxy your footage as necessary.  You can either use your NLE’s native conversion tools, or you can use Mpeg Streamclip, Clipwrap, or Adobe Media Encoder.  Preserve the native frame rate – don’t try to convert to 24p yet.

Achieving Smooth 24p, 100% Speed (non-slow motion)

Here’s the problem with 60p and 30p: they don’t divide into 24 by any whole number.  60/24 = 2.5, so you’re dropping every third frame.  30/24 is 1.25 and creates the same issue.  This results in jerky playback.  For easily achieving smooth playback, I recommend FCP X.

Rate Conform in FCP X for smoother playback

The key to smoothing the playback in FCP X is a tool called “Rate Conform” and is located in your Inspector in Video, below Spatial Conform.  You have four options here:

  • Floor: drops every third frame. Use on shots with little motion.
  • Nearest Neighbor: similar to Floor but is mathematically somehow different; it doesn’t really matter.  Just try it on shots that don’t quite look smooth with floor.
  • Frame Blending: blends nearby frames to create in-between frames.  Works well on shots with a moderate amount of motion.  Slow-moving subjects look better.  If someone is waving a hand, or walking across frame against a contrasting background, it will probably look bad.
  • Optical Flow: creates in-between frames by morphing.  Creates the smoothest results of the three.  Takes forever to render. Use on the toughest shots.

Note that your jerky motion could also be related to using the wrong shutter speed when shooting.

If you’re shooting a fast-moving subject at 1/60 or above, it might look fine at 60p, but atrocious at 24p.  To fix this, I recommend ReelSmart Motion Blur.  This plug-in adds back the motion blur missing in your footage to create a smoother overall look.  Just drag and drop the effect on the clip in your 24p timeline, and it will automatically fix the blur.  No tweaking necessary unless you notice too many warping artifacts.  Be aware that this will increase render time significantly.

If you don’t use FCP X:

For all other major NLE programs, you can still use ReelSmart Motion Blur.  You can also use the plugin Twixtor to create the same effect as Optical Flow – creating smooth in-between frames.   Click here for a tutorial on using Twixtor in Adobe After Effects.

Slow Motion

Achieving smooth slow-mo is much simpler, so I’ll only briefly touch on this.  Again, I recommend FCP X for the easiest and most flexible slow motion.

In FCP X:

  • Select your clip in the timeline
  • Modify > Retime > Conform Speed
  • Or select a clip in the timeline > hold Command + R > drag the top right  corner of the clip in the timeline.

In FCP 7: Follow this link for a video tutorial.

In Premiere Pro: Follow this link for a video tutorial.

In iMovie: Follow this link for a tutorial.  But don’t use iMovie.  Seriously.

Feel free to ask questions – I will happily update this article to include any missing info!