This month's edition of DV has a great article on lighting. Jay Holben discusses how to diffuse light, thereby creating "a long transition between light and shadow".
He writes, "Many filmmakers who are new to lighting know that they want softer light...so they put diffusion on the face of their lights. Unfortunately, this has very little effect...If, however, you put that diffusion out away from the [barn]doors and fill it with the light, it becomes a much larger source and much softer light."
The article is a little tricky to access. After you go to DV's website, click on the magazine icon near the upper left corner of the browser window. A new window will appear and the full magazine will download.
The article is on pages 45 and 46 and is entitled "Character Study". Good stuff.