"Raiders of the Lost Ark" bears the mark of Spielberg's directorial style. The film is heavy in special effects, including lighting techniques. Spielberg is known for precision in his use of lighting, angles and lenses. Such precision creates realistic shots while maintaining the visual excitement of the scenes.
"Raiders of the Lost Ark" features a number of interior scenes that had to be carefully lit to make the action visible while preserving the feel of authenticity. For example, in scenes where the characters explore the archaeological sites, Spielberg used a four-point lighting setup with reflectors to manipulate the shadows (which are an important visual flourish in such scenes.)
One of the striking features of "Raiders of the Lost Ark" is its use of natural light. Spielberg took advantage of the bright light of the Tunisian desert (where parts of the movie were shot). The director uses the light of the setting sun in a dramatic, wide-angle view of workers toiling in the desert. Most of the city street scenes were also filmed while taking advantage of the clear, vivid daytime light.
Chiaroscuro is a visual design technique that contrasts light and dark areas. It was used to great effect in Renaissance portraiture and in film noir; it's also used repeatedly in "Raiders of the Lost Ark." For example, in shots with two individuals Spielberg often frames one in light and one in shadow. Dark lighting is used to communicate mystery or ill intentions (as used to characterize the Nazis in the film). Chiaroscuro is also employed in the scene in which the sun sets behind silhouetted figures working in the sands.