imovie canvas size

iMovie 10 only works in 16:9 aspect ratio but 750 x 1334 is 9:16. You could edit on its side then rotate it after sharing but of course titles would be a problem. You would have to create them in another app with as .png s with transparent background or .jpgs with green background then use the green screen facility

Geoff.

The iMovie canvas is 16x9 and you cannot set custom aspect ratios. Your dimensions are close to 9x16 so you can add your clip to the timeline and select crop tool and choose fit. Of course you will have side bars, but you can rotate the clip to aide in editing and rotate back to share.