Turn your letterboxed 4:3 files into 16:9

We all know how cool MPEG Streamclip is and how we couldn’t live without it.  But did you ever wonder what those settings for Zoom and X/Y were down at the bottom of the settings box?  Turns out if you know what you’re doing you can use those settings to crop the letterbox on a 4:3 file and output a 16:9 file.  Nice little trick if you ever need it.