dodge white backgrounds

I do a great deal of portraits on a white background and making that background white is difficult with lighting. You could set your background light to two stops brighter than your main light but this also usually produces flare or interferes in some way with your subject. I dont worry too much about this because i have a dodge tool in photoshop that works quite well. Set the tools mode to highlights in its option bar and the strength quite low (10 - 18). Use a nice soft brush, not too small, and go over the white areas of your background. It should not affect your subject unless they too are wearing white.