How do I keep the size of my video after converting?

So my original video size is 1920x1080. But when I import it to Final Cut, it requires rendering. Therefore, I convert my videos using Mpeg Streamclip. I export as Quick Time and compressed to Apple DV/DVCPRO NTSC, frame size of 1920x1080(HDTV 1080i).

Now, when I upload it to final cut, the rendering issue is fine but the video size shrunk. Like it shrunk down to 720x480, even though I exported as 1920x1080?

How do I make the video size to remain the same but change the format to fit final cut rendering issue!!??