A graduated backdrop can eliminate any unwanted shadows that can be created by strong studio lighting. To create a graduated backdrop you will need an off-camera strobe flash, a grid spot and a remote flash trigger. Also, use a simple photographic backdrop placed behind your subject in a color that will complement the subject’s outfit.
Set up for your portrait as you would normally, including rim, fill and key lights. When placed on the flash head of the camera, the grid spot, will force the light from the flash to be more direct. This will give you more control over the lighting.
Set the flash so it points toward the area of the photographic background where the shadow from the subject will be cast. To find where the shadow will be cast, position the key light in place and shoot sample flashes. To ensure you will get the desired background effect, take several sample photos at various exposures. You may have to experiment with lighting power, position and camera setting until you get the desired effect. Remember, the key to finding the right background and lighting effects is experience and experimentation.