Queen Sized Softbox
Here is an instance where I wanted to create an image with the background completely white and the subject in front correctly exposed. So I was in a situation where I was taking pictures with a large south facing window that would have light streaming in all day. To create the “softbox” effect I hung a semi transparent queen sized white sheet between two stands in front of the window. By placing the model close to the light source it allowed light to spill in from both sides. 
In order to deal with the great difference in light levels I metered for the models face and allowed the backdrop/ light source to clip. In addition a reflector was placed in front of the model for fill. The resulting exposure was F5.6 at 1/60 sec and ISO 250. This was actually 1 1/3 stops over what had been metered for the models face but helps give the high key look I was after. In order to get a warmer look the white balance can also be increased by about 1000 degrees, but in this case it was fine and I have left it as shot.
With the same setup, you can get a different look by using flash to light the subject while still clipping the white background. Here I placed an off camera flash with an umbrella reflector right above the camera.
Settings f2.8, 1/80 s at ISO 125. The flash output power was adjusted manually for the correct exposure.
