When you start a new video project you have to decide if you want it be comprised of photos or video clips. Now, I understand this can be a little confusing because no matter which option you choose, the end result will be a video. Each option can achieve a very different look. See exmaples below of videos made with video clips versus photo clips.
The video clips can range from 1/4 second, 1/2 second, 1 second, 2 seconds & 3 seconds.
When you create a project with photo clips, you have the option to customize how fast you want them to play. This option is currently only available for projects made up of photos.