Slow-motion videos are a fun option for iPhone and iPad videographers, letting you slow down the action for dramatic effect. If you have a iPhone 5S, you can shoot slo-mo videos at 120 frames per second, and if you have an iPhone 6 or later, you have two slo-mo options: 120fps and 240fps.
If you shoot a slow-motion video, you can return the video to regular speed. Or you can adjust the portion of the video that is slowed down.
To get started, open your video in the Photos app and tap Edit in the upper-right corner.
Below your video in edit mode, you will see a series of tick marks. The sections where the tick marks are tight together is regular-speed video, and the section where the tick marks are more spaced out is the slow-motion portion of the video. Two little sliders separate the slow-motion section from the regular-speed sections at the beginning and end.
To remove the slow-motion effect from your video and return it to regular speed, all you need to do is move the sliders at either end of the slow-motion section together. When the two sliders are aligned and all the tick marks are tight together, your video is regular speed from start to finish.
When you shoot a slo-mo video, by default the video features a few seconds at the beginning and end of regular motion. You can move the sliders to adjust how long the regular-motion intro and outro last, or slide the bars all the way to either end to make it so the entire video is slow-motion from start to finish. This flexibility allows you to start and stop the slow-motion effect at just the right points in your video.
Unfortunately, this edit tool is a one-way street. That is, you can’t take a video you shot in regular video mode and use the Photos app to add a slow-motion effect. You can do so, however, in iMovie for iOS. Learn how to add video effects in iMovie for iOS, including speeding up or slowing down portions of your video project. For more, read our complete guide to iMovie for iOS.
(Via WonderHowTo)