Getting my head around iMovie frame rates
A few months ago I started recording my fishing trips for a YouTube channel, starting with my iPhone and then buying an ORDRO EP7 head-mounted video camera for action shots. Both the ORDRO and the iPhone delivered video at 30 fps so I had no cause to worry about the effect of different frame rates.
Having now acquired a Panasonic HC-V380 camcorder to take over from my iPhone, offering quite spectacular zoom capabilities, I was concerned that the new camcorder delivers 50 fps, a significantly higher rate than the EP7, which I had set at 30 fps. I produced a short iMovie project with clips from both to see if this caused any problems, and it didn't seem to. Knowing that iMovie sets the resolution, and presumably the fps based on the first media clip added, I tried both combinations. It didn't seem to make any difference. I then discovered that iMovie had actually exported at 25 fps in each case and after some more trials found that this is a default, irrespective of the individual clip settings.
During all this experimentation I had increased the EP7 rate to 60 fps, as I found that iMovie would export at 60 fps if the first clip was set as such. Indeed, this was the case, but I had added as second clip from the camcorder set at 50 fps, which was totally ignored when iMovie rendered the output file.
So it seems that having now reset the EP7 to 30 fps, and with the camcorder at 50 fps, everything will be rendered at 25 fps and let's hope this doesn't lead to any issues with the output video. There will, after all, be too many frames rather than too few! During all this I couldn't find one article or forum discussion that explained this aspect of iMovie very clearly, although there were plenty of people trying to sort out the frame rate issue. Typing in 'frame rate' in iMovie Help yields no results.