Adjust zoom effects in iMovie on iPhone
The viewer in iMovie includes controls for adjusting zoom effects, including how big or small video clips appear during playback and how photos move using the Ken Burns effect.
Adjust the movement of photos with the Ken Burns effect
iMovie applies the Ken Burns effect to the photos you add to your project. With this effect, the camera appears to sweep across and zoom in and out of the photo. If there are people in the photo, iMovie uses face detection to keep faces within the viewing area.
You can adjust the Ken Burns effect so that the motion starts and ends on the parts of the image you specify.
In the timeline, tap the photo you want to adjust.
The Ken Burns effect controls appear in the lower-right corner of the image in the viewer.
To set the way the photo is framed at the beginning, tap the Start button
.Pinch to zoom in or out, then drag the image in the viewer to frame it the way you want.
To set the way the photo is framed at the end, tap the End button
.Pinch to zoom in or out, then drag the image in the viewer to frame it the way you want.
To close the controls, tap outside the clip.
To turn off the Ken Burns effect for the photo, tap Ken Burns Enabled 
. To turn on the Ken Burns effect, tap Ken Burns Disabled 
.
Adjust a video clip’s zoom level
With your project open, tap to select a video clip in the timeline.
To set the viewing area within the clip, tap the Zoom Control button
in the viewer.Pinch to zoom in or out, then drag the image in the viewer to frame it the way you want.
To preview your adjustments, tap the Play button
.