In my last couple of years of digital photography I have a few curiosities. As of late, I am curious as to why images downloaded (as Preview) are only 160 kbs, and when converted to PS format (same image size with no corrections whatsoever) the size jumps to 580 kbs. Same file but much larger??? What am I gaining by converting them to PS files? I like to keep all my image files in the same type, but if they're going to be so much larger, what's the sense?