Portrait photographers use a main light, often called a key light. In studios, the fill light may look like a sideways umbrella that emits a bright spotlight onto the subject. The main light gives shape to the object and is usually placed off to the side with the light shining onto the subject's body. The key light is also usually slightly above to shine down into the eyes, creating a shadow on the opposite side of the face when turned towards the light. When posing your subject and the main light source, place your subject as close to the light as possible without it being in the shot.
To highlight the hair and increase shadows around the subject, an overhead light casts a shine down onto the head. The overhead light also creates shadows on the background, so two light boxes are also used to show the colors of the background if the photographer finds the background to be necessary for the shot. For example, in the case of a school photo, students pick out the color of a background, so light boxes in addition to a hair light produce all the light necessary to create the right shadows and highlights on the hair and background.
To create an overall light in the photo, photographers use a flex fill light. A flex fill suspends a light from a stand. A portrait photographer places this light to either side of the subject, moving the stand back and forth to test out different highlights and shadows on the body. A flex fill is usually a soft light that only slightly brightens or darkens a subject depending on its proximity. Photographers usually have an assistant that moves the flex fill and key light around the subject, changing the distance by inches or feet to achieve the desired effect. For example, when both the flex fill and main light are placed 1 foot from the subject, most of the shadows and color are drained from the face. When placed 3 feet from the subject, the light diminishes and creates more color tones and shadows.
A background light is placed on the floor behind a subject pointed toward the background. Like the light boxes used in combination with the hair light, the background light highlights the colors of the background. However, portrait photographers create shadow portraits and silhouettes using the background light as the only source of light in a photo. For example, with all other lights turned off except for the background light, the subject sits in front and poses, the background is illuminated brightly in contrast to the subject, who is left in shadow. By moving the background light up and down on a stand behind the subject, you can create different shadows to highlight parts of the subject's body while still achieving a silhouette.