For the first photograph, I made the exposure by using only a softbox as the main light. The softbox had been positioned fairly close to the subject at a 40-45 degree angle. As a result, only one side of the model's face was brightened, and there are some distracting shadows on the opposite side; also the key triangle is not  clear in this picture.

     In the next two photographs, I used two light sources---main light and fill light: the difference in these photos was created by adjusting the distance between the model and the fill light. In the second photo, the fill light was used; so the shadows on the model's face are brightened, and the contrast between shadows and highlights is softer compared to the first photograph. Yet its edge of the shadows is still clear, since the fill light was placed far and the light was weaker than the main light: The light was not so strong enough to cover the whole shadows.

     In the third photograph, fill light placed near the subject covered most shadows on the model's face: In this case, the brightness was enough to cover up the shadows created by the main light, and the contrast---change in the brightness---is softer than that of the last two photographs.