Need help backing up iMovie files to portable drive.

What you can do is to move your iMovie library to an external drive, so all projects will be created there and you will free up space.

To do it, you just have to go to Movies folder and move the iMovie library to an external drive. You can also finish your projects by creating the movies there, so you will free up even more space, and you will have only the iMovie app on your iMac's hard drive.

I recommend you to put the iMovie library on an external drive formatted in Mac OS Extended (Journaled)

Within iMovie itself you can move the files. Make sure your external drive is connected, start up iMovie then go to the help menu. Search for "move events". You will get complete instructions on how to move, copy, etc. Basically, you drag the event or project from it's curent location to the destination drive as listed in the left hand side bar. YOu will have options to move and erase, or simply copy.

My strategy is to import my video into iMovie on my internal drive, do any project/editing work there as it will be a tad faster. When I am finished with it then I move the project and event files to an external disk with the option of erasing it from my internal.

Hope this helps.

BF

Apple explains how to move the whole library to an external HD (EHD) in their article called:

iMovie: How to move the Library to an EHD

This is what I'd recommend you do, it will save HD space on your iMac. You should also have a second HD available to be backing up your total computer system using Time Machine. DO NOT use the same EHD to backup and store media!!!!!!