I'm going to be shooting a series of fashion shots tomorrow however I can't keep my background white, at the moment the set up is 2 interfit halogen hot lights with one diffuser brolly and one reflector brolly to light the subject and 2 smaller workmans halogen lights to light the background which in this case is a white sheet stretched over a custom built frame. I tried intentionally overexposing the images by a couple of stops and it results in a still slightly off white background and a blown out subject. I have set the white balance according to the manufacturers spec Kelvin for the lights we have also. These are full length model shots by the way and i'm shooting on my Canon 20D, i'd like to be able to avoid a lot of photoshopping as i'll be shooting in excess of 100 images. Any ideas on what I can do to sort this out would be much appreciated.