If you are looking for a free solution to slow down 60 frames per second (FPS) AKA 60p footage to get a slow motion effect on your Mac, you can download and install the freeware video de-interlacer JSE Deinterlacer. This will allow you to export your video at a slower framerate like 24FPS through stretching the film to be double length and use the additional frames shot to fill the time, kind of like stretching out a coiled spring. Fast frame rates are now available from the Canon 7d and 550d cameras with signs that many more cameras follow suit by offering this feature, thus the reason to offer a no-cost option of how to handle the footage.
Step one: Import
Step Two: Project settings
This is the main part we need to care about. Ensure you have Deinterlace selected from the options and Both fields and Double movie duration checked. Normal height and Adaptive will be selected by default, this is what we want.
Step 3: Output
Step 4: Movie Settings
Step 5: Video Settings
Step 6: Finishing up
Now you can return back to the output screen and select Ok, this will start the conversion process off that could take some time depending on the size of your source video. Once you have converted your video, you can take it into your choice of video editing suites such as iMovie.