50i doesn't mean 50fps. It means 50 interlaced FIELDS...and since there are two field per second, that's 25fps. Just like 60i is 60 interlaced fields at 30fps. Confusing? Yup. I hate labeling things that way.
So, your footage is 25fps. But, you want to use it in a project with a frame rate of 60? That's a standards conversion. PAL to NTSC. That's a difficult thing to do and make it look right.
I understand the concept of interlacing, but this is what I thought: If I film in 50i, the cam takes frames two times faster than at 25p. It takes only half frames, though. I hoped, that by De-Interlacing, I could reconstruct part of the missing information, so that I get results that are – of course – not true 50p, but something that's more fluent than 25p.
Did I get that wrong? False expectation? Is the 50i spec only marketing bulls#§"?
Would be cool if someone could clarify this for me...