iMovie won't let me make transitions shorter than 1 second

Hi,

I'm not able to replicate your situation. If I double click on the transition in the timeline and enter 0.5 seconds in the duration box, I get a transition of 1/2 second.

If that is not happening in your case, try deleting preferences. To delete preferences, open iMovie while holding down the Option and Command keys and select to delete preferences in the box that appears. iMovie will

open in a new empty library. If so, reopen your old library to get back to your projects. Possibly you may need to reboot to set the changes.  Deleting preferences is a safe procedure that will not cause data loss or disruption to your project.

-- Rich

I suggest you ask here: https://discussions.apple.com/community/applications-services/imovie