So I'm making a feature film. My camera only shoots mp4 files. I can import mp4 files into premiere, but after a while I start having trouble editing, or I get a grey or media pending screen instead of video. I don't have enough drive space to convert to prores for a whole feature. My question is, what other choices do I have? What file/container/codec format can I convert to that keeps file sizes in the range of mp4s, but that flow well for editing in Premiere? Please help. Thanks.
You can try the new Premiere PROXY workflow, where you make proxies and then relink to the masters later. Offline/online editing.
But really, any "full resolution" codec you cut with, that will be EASY to cut, will be larger. The larger data rate means less compression, and less work for the hardware to decompress on the fly...like what happens when you try to edit AVCHD or H.264 on the fly.