Very new to editing in premiere, I'm making a sequence which has mixed in footage at 30, 24 and 12 fps. I merged it all into 1 in order to speed up the video slighlty (has to be under 3 min), and exported. But "match source" says that the sequence's framarate is 12 fps. Can I just change it to 30, or will that generate issues?
I would advise you to transcode the 12 fps footage to 24 (or is it 23,976?). This is the most challenging step, as either your computer will need to create the missing frames, or you'll have to double the speed of the original footage.
The translation of 30 to 24 will be handled by PPro internally without much problems, I expect.
I would just like everything to look as it did before I merged it. The stop motion to remain at 12 fps, the 2d animation at 24, and the real life footage at 30 (I explained myself pretty badly, which is why I'm saying this). If your solution allows for this, please tell me how to do this.
PPro cannot magically switch between framerates in a single sequence, so you have to make a choice on what your destination will be. It can be any framerate, but given that you'll likely want to use it somewhere online, 24 or 30 are your best bets in NTSC areas of thr world. In other parts it would be 25fps.