Your new camcorder shoots 50 or 60 frames per second? But nor iMovie nor FCPX handle thes type of videos!
Convert to edit them …And enjoy its "too many frames" to produces a slow-motion (what's the aim of a too much detailed movie if you cannot play with it).
Movie50p60p is especially designed for them.
Use your videos on Mac: easily, promptly and without quality lose.