The 250 watt halogen bulb was placed behind a large sheet of vellum, transforming a point light source into one that is both giant and diffuse. Fill light was not necessary because the large light source could be seen by all portions of Gemma's face. We can also observe light's exponential decay in intensity given the portion of Gemma's face closest to the vellum is brightest.
Two large flags were positioned parallel to each other a couple inches apart, creating a diagonal slit to place the halogen bulb within. Because light travels in a straight line, the only parts of Gemma's face that were illuminated were those that could see the light bulb between the flags.