How to export 120fps video from iPhone?

Question

Hello,
I've been on all day trying to find the answer to this question.... this is what I'd like to do:
I'm experimenting with slow motion in Final Cut Pro X. As I understand it, shooting at a higher frame rate will yield better results.
My camcorders only shoot at 50i or PF25.
I'm looking for a Camcorder that will shoot at 60fps or higher, but then it occurred to me that my iPhone 5s will shoot at 120fps in the slow mo setting.
So, I tried shooting something in this way and then emailed it to myself. My intention was to import the 120fps into Final Cut Pro X. As I understand it, FCPX will only handle up to 60fps(?).
Using the 'Optical Flow' in FCPX seems fairly straight forward, so.......
Do I really need to go out and buy another camcorder, or can I shoot at 120fps on the iPhone then import that into FCPX then use 'Optical Flow'?
* I don't want to use the option of slowing the footage down on the iPhone though *
I believe I have to do something in Final Cut Pro to make the footage playback properly, and make it conform or something...
If anyone can help please do so. I can't find simple step by step instructions on how to do this.
Thanks in advance!!!

Answer 1

Thank you so much for your reply fox_m.
You've made it clear to me that the iPhone 5s does indeed record at 120fps when using the slow mo function. I've taken your advice and imported the footage (rather than email it to myself) and after using a program called 'Mediainfo' I can see that it is indeed 120fps.
Great! So before I go out and buy a Camcorder that can shoot at 60fps, I can experiment with the iPhone 5s and FCPX.
Mathematically I think I'm with you on your explanation of 25% being 1 complete frame etc. (I think).
Would you be so kind as to help me out with a few more queries?
1: I've read that I should convert the footage to ProRes. So I used MPEG Steamclip to convert my footage. Now I don't know how necessary this is, but I noticed it turned a file that was around 30mb into a file that's 300mb. Do I have to convert files to ProRes?
When I import the 120fps footage I get this:
I click 'OK'.
2. Is that right?
3. Do I have to 'Conform' the footage? I don't seem to have the option though? I have this:
But, I don't know what this is!?
Lastly, it's this type of look I'm after...
http://vimeo.com/28234381
So, rather than just slowing down by 25%, I'd like to slow down a bit more like in this guys video.
I'm messing around but all the Conform, ProRes things have me worried I'm not doing it right.
How would you do it fox_m??
Many thanks for any help I really appreciate it.