One of the fun new features of the iPhone 5S is the ability to shoot slow motion video. One of the not so fun features of iOS 7 is the non-destructive editing of images and videos, which basically means that anything you do to an image or video on your phone is not readable by anything outside of your phone.
I recorded a small clip of my son throwing corn from a fall festival in the air. On my phone, the slow motion was very cool. I imported the video to my computer using Lightroom and the image played at normal speed.
Slow motion on the iPhone works by recording 120 frames per second (fps) and then replaying the captured video at 30 fps. The benefit to doing slow motion this way is that you have enough raw data / stills to play cleanly at 30 fps. If you shoot a video at 30 fps and try to render slow motion at a quarter speed, then you would use 7.5 fps and the software would have to some how make those 7.5 frames last a full second. Some software does it better than others, but generally it introduces a lot of ghosting and artifacts to the final video. By recording more frames and slowing them down, you get a better quality slow motion output.
When you take that video off the phone, though, applications will play the clip at 120 frames a second, which is “normal” speed for the clip. What we need to do is reproduce what the iPhone does and play our 120 fps clip at 30 fps.
Fortunately, you can use iMovie to recreate the slow motion effect. Here’s how…
Connect your iPhone.
Select the video from your iPhone and import it.
Once the video is imported, if you look at the clip in iMove you’ll see a “120″ tag inside preview. That indicates that the clip was recorded at 120 fps.
Next, add the video to your project.
Select the clip and navigate to Clip > Slow Motion > 25%.
If you haven’t already done so, you will get prompted to optimize the clip before the speed can be adjusted.
Once the clip has been adjusted, it will appear 4 times longer in your project. Recorded at 120 fps played at 1/4 speed = 30 fps.