My Sony HandyCam HDR-SR11 takes HUGE file sizes for videos, can I lower it?

Questions:
I own a Sony HandyCam AVCHD HDR-SR11 video camera and I use it to record high-definition video game gameplay. My only issue is that the camera creates very, very large video files that take forever to import into iMovie and then to export, and then to upload to YouTube. If there is any way to make the file size smaller so that these times can be cut down, I would appreciate it!