At our productions we often shoot overcranked, which means we shoot at a higher framerate than 25 to get a slow-motion effect. I like 32 frames-per-second, but 37 and 48 are also nice. The highest in normal cameras is 60fps, the RED can go to 120 in full rez and the FS700 goes to 240 in 1080p.
The letdown of overcranking-mode is usually the loss of audio-recording. So I often use 720p50 as recording mode, so I can have the audio and record in 50 frames-per-second. During the edit I then decide if I want the normal speed, the audio and/or the slow-motion. Mind you our normal timelines are at 25 frames-per-second. So the 720p50 material sticks out a bit and needs special treatment to actually be interpreted as 720p25.
In FCP7 to go the correct way of conforming the clips 720p50 clips so they play in slow-motion you would have to identify them, duplicate the original clips (to keep them untouched), then import the clones into cinema-tools (which was part of the Final Cut Studio product) and conform them (which is a destructive process!) and then re-import into FCP7.
In FCPX....much easier.
Here is a clip from our recent Peakbreak production.
The Inspector says it is a 720p clip at 50 fps.
In the 720p25 timeline it behaves like a normal clip (and would also in a 1080p25 timeline). But it would be resized of course. Here is the timeline setup:
The clip as approximately 25 Seconds; that´s the original time of the live-action.
Now comes the trick: Go to MODIFY > RETIME > CONFORM (I mapped the letter "4" for this menu-item)
And voila: without a roundtrip to cinema-tools and without any destructive messing with my quicktime or in this case XF-file, the clip is running in 25p now (doubling its length).
I have used this method also with 29.97 and 24fps material and it works visually flawless. But especially in conforming from 30 down to 25 you need to adjust the pitch of the audio!