Had to resort to using ffmpeg to create a timelapse because iMovie doesn’t let you do 4:3 movies for some reason, and I didn’t want to download a new video editor.

In a directory where the photos are named photo-00001.JPG to photo-00456.JPG (using macOS Finder’s batch renaming tool)

ffmpeg -f image2 -r 10  -i photo-%05d.JPG \
    -c:v h264_videotoolbox -b:v 8500k \
    -preset slowest -profile:v high \
    -allow_sw 1 output.mp4

-r 10 tells it to use 10 images per second